SOFTIMAGE|XSI

SOFTIMAGE®|XSI™
Version 1.0
Modeling & Deformations
a
Modeling & Deformations was written by Grahame Fuller, edited by
Edna Kruger and John Woolfrey, and formatted by Luc Langevin.
© 1999–2000 Avid Technology, Inc. All rights reserved.
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of their respective owners.
The SOFTIMAGE|XSI application uses JScript and Visual Basic Scripting
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Printed in Canada.
Document No. 0130-04615-01 0400
Contents
Contents
Roadmap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9
About This Guide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Where to Find Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Document Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Section I • Modeling
Chapter 1
Basic Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
Types of Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
Building Blocks of Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Centers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Geometry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Objects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Clusters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Normals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Useful Tools for Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Transformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Geometric Approximation Parameters . . . . . . . . . . . . . . . . . . . . . . .27
Visibility, Display, and Selectability . . . . . . . . . . . . . . . . . . . . . . . . . .27
Hierarchies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
Layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
Duplicating and Instancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
Grid Display and Snapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
Info Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
Symmetry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
Operator Stack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
Viewing and Modifying Operators . . . . . . . . . . . . . . . . . . . . . . . . . .30
Deleting Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
Freezing the Operator Stack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
Modeling Relations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Breaking the Modeling Relation . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
Working with Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
Clusters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
Transforming Components and Clusters . . . . . . . . . . . . . . . . . . . . . .34
Deforming Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36
Modeling & Deformations • 3
Contents
Chapter 2
Polygons & Polygon Meshes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Creating Polygon Meshes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Getting Primitive Polygon Meshes . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Importing Polygon Meshes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Working with Polygon-Mesh Components . . . . . . . . . . . . . . . . . . . . . 41
Working with Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Working with Edges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Working with Polygons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Geometric Approximation on Polygon Meshes . . . . . . . . . . . . . . . . . . 48
Faceted and Smooth Polygons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Displacement Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Chapter 3
Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Types of Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Curve Components and Attributes . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Parameterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Multiknots. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Creating Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Primitive Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Drawing Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Creating Curves from Other Objects . . . . . . . . . . . . . . . . . . . . . . . . . 59
Modifying Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Inverting Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Opening and Closing Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
Shifting U on Curves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
Cleaning Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
Reparameterizing Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Stitching Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Working with Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Selecting Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Moving Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
Using Proportional Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
Adding and Deleting Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Chapter 4
Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Surface UV Parameterization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Components of Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Multiknot Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Creating Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Primitive Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Creating Surfaces from Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
Creating Surfaces from Other Surfaces . . . . . . . . . . . . . . . . . . . . . . . 87
Modifying Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Inverting Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Opening and Closing Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
Shifting UV on Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
4 • SOFTIMAGE|XSI
Contents
Swapping UV on Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93
Cleaning Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93
Reparameterizing Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93
Extending Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .95
Stitching Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .96
Working with Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .97
Selecting Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .97
Moving Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .98
Using Proportional Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .98
Working with Knots and Knot Curves . . . . . . . . . . . . . . . . . . . . . . . .100
Selecting Knot Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100
Adding Knot Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100
Removing Knot Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101
Chapter 5
Surface Meshes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103
Building Surface Meshes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .106
Considerations for Modeling Component Surfaces . . . . . . . . . . . . . .108
Junction Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .108
Multiknots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .111
Snapping Boundaries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .112
Snapping Boundaries with Different Numbers of Points . . . . . . . .112
Assembling Surface Meshes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .113
Applying the Continuity Manager . . . . . . . . . . . . . . . . . . . . . . . . . . .114
Working with Subsurfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115
Selecting Subsurfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115
Applying Local Materials and Textures . . . . . . . . . . . . . . . . . . . . . .115
Section II • Deformations
Chapter 6
Introduction to Deformations . . . . . . . . . . . . . . . . . . . . . . . . . . . .119
Considerations for Deformations . . . . . . . . . . . . . . . . . . . . . . . . . . . .122
Modifying Deformations in the Operator Stack . . . . . . . . . . . . . . . .123
Modifying Deformation Parameters . . . . . . . . . . . . . . . . . . . . . . . .123
Muting Deformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .124
Removing Deformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .124
Freezing the Operator Stack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .124
Weight Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .125
Creating Weight Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .125
Selecting Weight Maps. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .126
Painting Weights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .126
Deforming with Weight Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . .127
Connecting Deformation Parameters to Weight Maps . . . . . . . . .128
Mixing Weight Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .128
Setting Weight-Map Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . .129
Freezing Weight Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .129
Modeling & Deformations • 5
Contents
Chapter 7
Basic Deformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
Applying Basic Deformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
Chapter 8
Deforming by Cluster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
Cluster Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
Creating a Cluster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
Selecting Clusters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
Viewing Clusters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
Adding Components to Clusters . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
Removing Components from Clusters. . . . . . . . . . . . . . . . . . . . . . . 143
Clusters’ Last Stand. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
Animating Clusters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
Deforming by Cluster Centers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
Chapter 9
Spatial Deformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
Deforming by Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
Deforming by Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
Deforming by Lattices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
Creating and Applying Lattices . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
Applying an Existing Lattice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
Setting Lattice Deformation Properties . . . . . . . . . . . . . . . . . . . . . 155
Deforming by Spines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
Modifying Spine Weights . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
C ha p t e r 10
Shrinkwrap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
Sample Uses of Shrinkwrap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
Types of Projection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
Other Shrinkwrap Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
Shrinkwrap and the Modeling Relation . . . . . . . . . . . . . . . . . . . . . 166
Shrinkwrapping toward an Inner Object . . . . . . . . . . . . . . . . . . . . . . 167
Shrinkwrapping toward the Target’s Center . . . . . . . . . . . . . . . . . . . 168
Shrinkwrapping along an Axis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
C ha p t e r 11
Waves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
Wave Control Objects and Wave Operators . . . . . . . . . . . . . . . . . . 173
Making Waves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
Wave Control Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
Creating Wave Control Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
Setting the Wave Shape. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
Controlling Periodicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
Controlling Speed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
Controlling Falloff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
Transforming the Wave Control Object . . . . . . . . . . . . . . . . . . . . . 176
6 • SOFTIMAGE|XSI
Contents
Wave Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .177
Applying Wave Deformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . .177
Editing Wave Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .178
C ha p t e r 12
Quickstretch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .179
Object Centers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .181
Object Subdivisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .182
Applying Quickstretch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183
Creating a Quickstretch Deformation . . . . . . . . . . . . . . . . . . . . . . .183
Viewing a Quickstretch Deformation . . . . . . . . . . . . . . . . . . . . . . .183
Motion Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .184
Quickstretch Deformation Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . .185
Flexing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .185
Stretching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .185
Yielding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .185
Editing Quickstretch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .186
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .187
Modeling & Deformations • 7
Contents
8 • SOFTIMAGE|XSI
Roadmap
Modeling & Deformations • 9
Roadmap
10 • SOFTIMAGE|XSI
About This Guide
About This Guide
Modeling & Deformations describes how to build and sculpt the objects you
will animate in SOFTIMAGE®|XSI™.
• Chapter 1: Basic Modeling—covers some underlying principles of
modeling as well as some common techniques.
• Chapter 2: Polygons & Polygon Meshes—lists the available tools for
manipulating polygon meshes.
• Chapter 3: Curves—how to create curves for building surfaces, controlling
deformations, and using as paths or trajectories.
• Chapter 4: Surfaces—describes the many tools available for creating and
modifying NURBS surface objects.
• Chapter 5: Surface Meshes—explains how to assemble a single, seamless
surface-mesh object out of multiple surfaces.
• Chapter 6: Introduction to Deformations—covers some underlying
principles common to most or all deformations, including how to use
weight maps and paint weights.
• Chapter 7: Basic Deformations—describes some simple deformations that
can be applied to objects, including Twist, Bend, Push, and others.
• Chapter 8: Deforming by Cluster—how to deform objects using groups of
components, as well as how to assign a center to a cluster.
• Chapter 9: Spatial Deformations—how to deform objects using curves,
surfaces, and lattices.
• Chapter 10: Shrinkwrap—how to project an object onto the surface of
another object.
• Chapter 11: Waves—how to apply a wave to an object to create an
animated deformation.
• Chapter 12: Quickstretch—how to make an object stretch, flex, or yield
automatically as it moves.
Modeling & Deformations • 11
Roadmap
Where to Find Information
The SOFTIMAGE|XSI package includes a comprehensive set of learning
materials. Use this Roadmap to find the information you need to get up and
running quickly and effectively.
Start with the Setup Guide to install and license all components.
Setup Online Help is also available as you go through the process.
We recommend you choose Custom install so that you can perform the tutorials.
Refer to Release Notes, an online listing of known problems and limitations for this
version. Also includes workarounds and supplemental information. Access through the
web at www.softimage.com > support.
Follow the Guided Tour (available from the Online Library CD).
This is a set of videoclips that provide overviews of features and tools.
Work through Tutorials to learn the features in the context of basic productions.
This is a full-color set of lessons showing you step-by-step how to perform typical tasks.
You can install the scenes from the Software CD. (Choose Custom install when installing
SOFTIMAGE|XSI). Then choose the Content option to install the Tutorials project.
The Softimage Discussion Group
You can join the worldwide network of Softimage users exchanging ideas and techniques
by e-mail. To find out more, e-mail [email protected] Leave the Subject line
empty and type the word “help” in the body of your mail message.
12 • SOFTIMAGE|XSI
Where to Find Information
The Global Index & Glossary is an
index to all user guides and Tutorials;
a glossary of terms; and a list of
books, videos, and web sites related
to the 3D animation industry.
The user guides contain
conceptual information and
procedures on how to use
specific tools. These comprise:
• Fundamentals
• Animating
• Modeling & Deformations
• Shaders, Lights & Cameras
• Rendering
The Online Library CD
The Online Library contains
the Guided Tour and all the
SOFTIMAGE|XSI and some
mental ray documentation in
electronic form in both PDF
and HTML formats. (See next
page for how to use.)
Online Help
On-screen reference
information on interface
elements, commands, and
parameters. There are two
ways to access it:
• Click the ? button in any
property editor or tool view.
• Choose Help >
Contents and Index
from the main-menu bar.
Using SOFTIMAGE|3D with
SOFTIMAGE|XSI provides tips and
techniques about using the two
software packages. Available from
the Online Library CD and
softimage.com > support only)
HTML Scripting Reference
An HTML-based reference help on the syntax
for all scripting commands and arguments.
It appears in your default HTML browser.
Click on the icon (above) to open the script editor,
then click Help > Scripting Reference or press F1.
Pin up the SOFTIMAGE|XSI Interface Layout and the Quick Reference Card
to help you become familiar with the interface and keyboard shortcuts.
Modeling & Deformations • 13
Roadmap
Using the Online Library
The Online Library contains the Guided Tour and all the SOFTIMAGE|XSI
and some mental ray documentation in electronic form in both PDF and
HTML formats.
For full-text searching and printing, we recommend PDF format. If you do
not have Acrobat Reader installed, you can install it it free of charge from the
Online Library CD: Follow the instructions in the readme file on the CD.
To access the Online Library
1. Insert the Online Library CD in your disk drive.
2. Open one of the following documents:
- mainmenu.pdf (PDF format)
- mainmenu.htm (HTML format)
Document Conventions
The following are ways that information is displayed in the SOFTIMAGE|XSI
documentation.
Typography Conventions
14 • SOFTIMAGE|XSI
Type style
Usage
Bold
Menu commands, dialog-box and property-editor options, and
file and directory names.
Italics
Definitions and emphasized words.
Courier
Text that you must type exactly as it appears. For example, if you
are asked to type mkdir style, you would type these
characters and the spacing between words exactly as they are
appear in this book.
>
The arrow (>) indicates menu commands (and subcommands) in
the order that you choose them: Menu name > Command
name. For example, when you see File > Open, it means to
open the File menu and then choose the Open command.
Document Conventions
Visual Identifiers
These icons help identify certain types of information:
Notes are used for information that is an aside to the text. Notes are
reminders or contain important information.
Tips are useful tidbits of information, workarounds, and shortcuts
that you might find helpful in a particular situation.
The 3D icon indicates information about differences in workflow or
concepts between SOFTIMAGE|3D and SOFTIMAGE|XSI. You will
find these very helpful when working with the two products.
Warnings are used when you can lose or damage information, such
as deleting data or not being able to easily undo an action. Warnings
always appear before you are about to do such a task!
Keyboard and Mouse Conventions
SOFTIMAGE|XSI uses a three-button mouse for most operations. These are
referred to as the left, middle, and right mouse buttons. In many cases, you will
use the different buttons to perform different operations; always use the left
mouse button unless otherwise stated.
The two-button mouse is not supported in SOFTIMAGE|XSI.
This table shows the terms relating to the mouse and keyboard.
When this term is
used...
...it means this
Click
Quickly press and release the left mouse button. Always use
the left mouse button unless otherwise stated.
Middle-click
Quickly press and release the middle mouse button of a
three-button mouse.
Right-click
Quickly press and release the right mouse button.
Double-click
Quickly click the left mouse button twice.
Shift+click,
Ctrl+click, Alt+click
Hold down the Shift, Ctrl, or Alt key as you click a mouse
button.
Drag
Hold down the left mouse button as you move the mouse.
Alt+key, Ctrl+key,
Shift+key
Hold down the first key as you press the second key. For
example, “Press Alt+Enter” means to hold down the Alt key
as you press the Enter key.
Modeling & Deformations • 15
Roadmap
16 • SOFTIMAGE|XSI
Section I • Modeling
Chapter 1
Basic Modeling
Modeling & Deformations • 19
Chapter 1 • Basic Modeling
20 • SOFTIMAGE|XSI
Modeling is the task of creating the objects that you will animate and render.
You can create objects by modifying predefined primitives, drawing curves to
build surfaces from, or importing from other software programs like
SOFTIMAGE|3D.
Types of Geometry
SOFTIMAGE|XSI offers several types of renderable geometry:
• Polygon meshes are quilts of polygons joined at their edges and vertices.
• Surfaces are NURBS (non-uniform rational B-splines) patches formed by
intersecting U and V isolines.
• Surface meshes are quilts of NURBS subsurfaces acting as a single
geometry. SOFTIMAGE|XSI gives you powerful tools to control the
continuity at the seams between subsurfaces.
In addition, there are several types of non-renderable geometry:
• Implicits are basic shapes defined by a mathematical formula. By
themselves, they are not renderable but can be used, for example, to define
bounding boxes when setting weights for envelopes or as control objects
for a character rig. They are also the starting point for primitive polygon
meshes and surfaces, which are actually primitives that have been
converted. Note that implicit objects are not exported to IGES format.
• Curves are NURBS of linear or higher degree. They are not renderable
because they have no thickness, but they have many uses. For example,
they can be used as the basis for constructing surfaces. They can also serve
as paths for objects to move along.
Modeling & Deformations • 21
Chapter 1 • Basic Modeling
• Nulls are simply points in space. They have many uses; for example,
setting constraints, organizing objects in hierarchies, and so on.
• Faces (including text) and metaballs are not supported. If you
import these objects from SOFTIMAGE|3D, they are converted
to polygon meshes.
• Bézier, B-Spline, and Cardinal curves and patches are not
supported. If you import these objects from SOFTIMAGE|3D,
they are converted to NURBS curves and surfaces.
• You cannot create text in SOFTIMAGE|XSI.
22 • SOFTIMAGE|XSI
Building Blocks of Modeling
Building Blocks of Modeling
Modeling is the process of creating and assembling basic shapes into a
representation of an object—you can group various objects together to work as
a model. How a model is built can also determine how it will be animated.
SOFTIMAGE|XSI is highly interactive, and it allows you to try different
approaches to modeling. By experimenting with different types of building
blocks, you can foresee problems you may encounter as a result of your design.
Here are the terms you will see in the course of using this guide.
Points
Objects in 3D space (polygons, curves, and surfaces) are made of points, with
each point being an XYZ location in space. Point coordinates provide the
minimum information from which SOFTIMAGE|XSI can calculate the
geometry for an element. When you model an object, you enter point
coordinates to define the size and shape of the element.
Points define
and control
the surface.
You can
display lines
between
points.
Centers
The 3D world has a center (called the origin) and each object in the 3D world
has its own center. The center is the reference for defining the object’s shape,
location, orientation, and size.
Object center
Modeling & Deformations • 23
Chapter 1 • Basic Modeling
This means that, for all practical purposes, the transformations you perform
on an object are really performed on the object’s center.
The center is related to the coordinate system you choose. For example, the
global center (called the origin) is the center of the 3D world in which you
are drawing.
When you create an object, its (local) center is located inside the object.
However, you can move this center to another location for performing
different modeling tasks.
This means you can transform objects using one of several possible
coordinate systems, with very different results.
Geometry
Geometry refers to the control points owned by an object, and these control
points are usually seen with objects that can be rendered. For example, a
cube’s geometry is composed of eight control points. By this definition, a
curve has geometry since it is also composed of one or more control points,
whereas nulls have no geometry.
Objects
Objects in SOFTIMAGE|XSI include polygon mesh, surface, curves, implicits,
and nulls, as well as lights, cameras, and control objects.
Predefined Primitives
The simplest objects to use are predefined objects called primitive objects.
These are basic 2D and 3D shapes such as circles, spheres, cubes, spirals,
multi-sided figures, and so on. These primitives can be used “as is” or
modified. Typically, you select a primitive form and then transform it and
combine it with other modified pieces, which is much easier than drawing it
point by point.
Primitives can be nulls, polygon mesh objects, curves, surfaces, implicits, or
control objects.
Nulls
A null has a center with no geometry, but it can still be transformed like any
other object. It is very useful as a reference tool—for precision modeling,
constraining animation, and building hierarchies of objects. It also provides
you with an easy way to indicate a precise spot or orientation.
24 • SOFTIMAGE|XSI
Building Blocks of Modeling
Polygon Meshes
Polygon mesh objects are made up of ... polygons! Polygons can be boxy, such
as the traditional cube, or smooth, depending on the number and size of
polygons used to create the object.
No matter how you define the object for modeling purposes, all objects are
tesselated into triangles during rendering.
Curves
Curves are defined by a set of control points. More precisely, they are a
collection of curve segments attached by their ends, or knots, to make a curve.
The look of the resulting curve varies depending on the manner of
interpolation between the control points.
Most of the time, you will draw a curve and model with the resulting profile.
You can also select a few predefined curves such as arcs or circles. Curves
come in various types, each with its characteristic behavior and possible
modeling uses.
Implicits
Implicits are basic shapes defined by a mathematical formula. By themselves,
they are not renderable but can be used, for example, to define bounding
boxes when setting weights for envelopes or as control objects for a character
rig. Note that implicit objects are not exported to IGES format.
Surfaces
A surface is an object made up of parametric surface curves, rather than
geometric polygons. Surface objects in SOFTIMAGE|XSI are NURBS. Most
operations that apply to curves apply equally to surfaces; however, surfaces
can also have textures applied to them, which curves cannot.
Modeling & Deformations • 25
Chapter 1 • Basic Modeling
Control Objects
Control objects are objects like waves, forces, and particle clouds that are not
rendered themselves but can be used to affect other objects.
Components
Components are like the atoms that make up objects. You can modify an
object by selecting and moving, adding, or deleting components such as
points. The components of polygon meshes include points, edges, and
polygons. The components of surfaces include points, knots, knot curves, and
boundaries, and the components of surface meshes are subsurfaces.
Clusters
Clusters are groups of components on an object. You can select, transform,
and deform clusters.
Normals
On polygon meshes and surfaces, the control points form closed areas. Normals
are vectors perpendicular to these closed areas on the surface, and their purpose
is to indicate the visible side of the object and its orientation to the camera.
Normals are computed to optimize shading between surface triangles.
Normals are represented by thin blue lines. To display them, make sure that
Show > Normals is on in a viewport.
When normals are oriented in the wrong direction, causing modeling or
rendering problems, you can invert them using Modify > Surface > Inverse
on the Model toolbar. If a surface object was generated from curves, you can
also invert its normals by inverting one or more of its generator curves with
Modify > Curve > Inverse.
Normals should point toward the camera.
Right
26 • SOFTIMAGE|XSI
Wrong
Useful Tools for Modeling
Useful Tools for Modeling
SOFTIMAGE|XSI provides several useful tools for modeling.
Transformations
As you model objects, you will be moving them around; that is, translating,
rotating, and scaling them and their components. For more information
about transformations in general, see Chapter 6: Working in 3D Space of the
Fundamentals guide.
Geometric
Approximation
Parameters
The geometric-approximation parameters control how the geometries of
objects are approximated—the number of steps drawn per curve segment,
and so on.
By default, a new scene defines the geometric-approximation parameters for
the Scene Root. This property is branch-propagated to all objects in the scene.
The Hardware Display parameters define the settings used for the OpenGL
display in the viewports, while the Surface, Surface Trim, Polygon Mesh, and
Displacement parameters define the settings used for rendering.
For more information about geometry approximation, see Geometric
Approximation on Polygon Meshes on page 48 as well as Setting an Object’s
Surface Approximation in Chapter 3 of the Rendering guide.
Steps = 3
Steps = 1
Geometric approximation: Setting the number of steps between knots on a surface
Visibility, Display,
and Selectability
Each object has visibility, display, and selectability parameters that can be set
independently of the camera settings for the viewports.
• The visibility parameters determine whether the object appears in the
viewports and when rendering.
• The display parameters control how the object appears as you select and
modify it.
• The selectability parameter controls whether you can select or pick the
object in a viewport. You can always select objects in the Explorer no
matter what the value of its selectability parameter.
Modeling & Deformations • 27
Chapter 1 • Basic Modeling
These parameters are propagated through hierarchies; an object can either
inherit its parent’s parameters or use its own local values. The global values
for a scene are stored in the Scene_Root model.
By changing these parameters, you can work faster by simplifying the tasks of
viewing, selecting, and navigating around your scene. For more information,
see Setting Object Visibility in Chapter 4, Setting Object Display in Chapter 4,
and Defining Object Selectability in Chapter 5 of the Fundamentals guide.
Hierarchies
To organize the objects of a scene into a hierarchy, you parent one element to
another—this lets you propagate properties down the hierarchy from the root
element. You can select an entire hierarchy at once in tree mode by right-clicking
on any member of the hierarchy, or select an individual branch by middle-clicking
on the top node of the branch you want. For example, when you select an object
in branch mode and translate it, its children are translated with it.
You can create hierarchies using the Parent button, or by dragging and
dropping nodes in the Explorer. For more information about hierarchies in
general, see Hierarchies in Chapter 5 of the Fundamentals guide.
Layers
Layers are a useful tool for organizing your scene. You can divide your scene
into layers and control the visibility, display, and selectability of all objects in a
layer at once. For more information, see Layers in Chapter 5 of the
Fundamentals guide.
Duplicating
and Instancing
You can quickly build objects with similar parts by duplicating and instancing
objects. A duplicate is simply a copy of another object, while an instance is a
“linked” copy—you can modify all instances by modifying the original object.
For more information, see Duplicating Objects in Chapter 5 of the
Fundamentals guide.
Grid Display
and Snapping
You can use the viewport grid as a guide for modeling.
You cannot snap to points or other geometry.
Displaying the Grid Options
The grid options are on the Visibility Settings property editor. To display them,
1. Do one of the following:
- To modify the setting for a particular viewport, choose Visibility
Options from the Show menu of that viewport.
or
- To modify the settings for all viewports, choose View > Visibility
Options from the main-menu bar.
2. Click Grid.
28 • SOFTIMAGE|XSI
Useful Tools for Modeling
Showing the Grid
Several settings control how the grid is displayed:
• You can show and hide the grid with the Show > Grid option in a
viewport. Alternatively, you can use the Grid option in the Show box on
the Grid page of the Visibility Settings property editor.
• To set the size and orientation of the grid, use the options in the Display
Setup box on the Grid page of the Visibility Settings property editor.
Grid Snapping
When adding or moving points and objects, you can align them to the grid by
activating snapping. The grid for snapping can be set independently of the
display grid; the options are located in the Snap Setup box on the Grid page of
the Visibility Settings property editor:
• The Plane options specify the plane in which snapping occurs.
• Enable U and Enable V activate snapping along the two axes independently.
The exact meaning of U and V depends on which plane is selected.
• U Step and V Step specify the granularity of the snapping plane.
Alternatively, you can temporarily activate snapping in both U and V while
moving points and objects by holding down modifier keys as you drag
the mouse:
• Shift snaps objects to the grid.
• Ctrl snaps objects in integral offsets of the Step values.
These temporary modifier keys use the U and V Step parameters set in the
Snap Setup box on the Grid page of the Visibility Settings property editor.
For rotations, Ctrl snaps in increments of 11.25 degrees. Shift has no effect
with rotations.
Info Selection
Select an object and choose Edit > Info Selection or press Shift+Enter to get
useful information about an object: name, type of geometry, number of
components, number of triangles when tesselated for rendering, and so on.
Symmetry
To make a symmetrical copy of an object or hierarchy, duplicate it then scale it
by –1 in the axis of symmetry. You can also set the scaling in the Duplicate
Options property editor. For more information about duplicating in general,
see Duplicating Objects in Chapter 5 of the Fundamentals guide.
Note that this method does not work with skeletons and envelopes.
Modeling & Deformations • 29
Chapter 1 • Basic Modeling
Operator Stack
The operator stack is fundamental to modeling in SOFTIMAGE|XSI. It is the
history of all the operators (such as deformation and topology modifications)
that have been applied to an object. At any time you can go back and modify
or delete them.
Viewing and
Modifying Operators
You can view the operator stack of an object in the Explorer or use the Select
or Property button on the Selection panel to see it. The operator stack is
under the first subnode of an object in the explorer, typically named Polygon
Mesh, NURBS Surface Mesh, NURBS Curve List, Null, and so on.
For example, suppose you get a primitive polygon mesh grid, apply a twist,
then randomize the surface. The operator stack shows the operators that have
been applied. You can open the property page of any operator by selecting it
and pressing Enter, or by clicking on its icon. Any changes you make are
passed up through the history and reflected in the object. You can:
• Change the size of the grid.
• Change the number of subdivisions.
• Change the angle, offset, and axis of the twist in Twist Op.
• Change the random displacement parameters in Randomize Op.
Deleting Operators
To delete an operator in the stack, simply select it and press the Delete key.
Freezing the
Operator Stack
When you are satisfied with an object, you can freeze its operator stack. This
removes the history—you can no longer go back and change values. However,
the object requires less memory and is quicker to update.
To freeze an object’s operator stack, select the object and choose Edit > Freeze
Operator Stack or click the Freeze button on the Edit panel.
• You can only freeze the entire operator stack; you cannot freeze
only the selected operators.
• Freezing an object node freezes the entire object, including
texture projections. To freeze just the generator and deformation
nodes, select the operator stack node before freezing.
30 • SOFTIMAGE|XSI
Modeling Relations
Modeling Relations
When you create objects from other objects, a modeling relation is
established. For example, if you create a surface by extruding one curve along
another curve, the resulting surface is linked to its generator curves. If you
modify the curves, the surface updates automatically. The modeling relation is
sometimes called construction history.
Modeling Relation
The road was created by extruding a crosssection along a guide. When the original
guide was deformed into a loop, the road
was updated automatically.
You can modify the generated object in any way you like; for example, by
moving points or applying a deformation. When you change the generators,
the object is updated and your modifications are preserved—the object does
not “snap” back to its generated shape the way it does in SOFTIMAGE|3D.
Modeling & Deformations • 31
Chapter 1 • Basic Modeling
1 The original curve
2 Surface created by revolution
3 Revolved surface modified by
moving points
3 MoveComponent operators
are added to the stack after
the Revolution.
4 The original curve is modified.
32 • SOFTIMAGE|XSI
4 The revolved surface automatically
updates to reflect the new curve
shape. The modifications you
made to the surface after
revolving are preserved.
Modeling Relations
Breaking the
Modeling Relation
To break the modeling relation, freeze the generated object’s operator stack as
described on page 30.
If you delete the generator (input) objects without freezing the
operator stack of the generated (output) object first, the output
object is removed from the scene. See Freezing the Operator Stack on
page 30.
If this happens accidentally, press Ctrl+z to undo.
Modeling & Deformations • 33
Chapter 1 • Basic Modeling
Working with Components
You can work with components of objects like points, edges, polygons, and
subsurfaces by selecting, transforming, and deforming them. You can select
various component types using the selection filters in the Selection panel as well
as with supra keys. These methods are described in the appropriate chapter:
Chapter 2: Polygons & Polygon Meshes on page 37, Chapter 3: Curves on page 51,
Chapter 4: Surfaces on page 73, and Chapter 5: Surface Meshes on page 103.
Clusters
Clusters are groups of components. To create a cluster, select components
then click the Cluster button on the Edit panel. For more information about
clusters in general, see Chapter 8: Deforming by Cluster on page 137.
Transforming
Components
and Clusters
You can transform selected components and clusters using the tools on the
Transform panel. For more information about transformations in general, see
Transforming Objects in Chapter 6 of the Fundamentals guide.
To scale components and clusters
To scale by dragging the mouse, click the Scale (s) button. Alternatively,
quickly press and release the x key to activate the Scale tool in sticky mode, or
press and hold the x key while dragging to scale in supra mode.
Use the left, middle, and right mouse buttons to scale in different axes. Click
on the x, y, and z icons to enable scaling on an individual axis, or Ctrl+click to
toggle-select axes. Press and hold the Shift key down while dragging to scale
uniformly in all selected axes.
To rotate components and clusters
To rotate by dragging the mouse, click the Rotate (r) button. Alternatively,
quickly press and release the c key to activate the Rotate tool in sticky mode,
or press and hold the c key while dragging to rotate in supra mode.
Use the left, middle, and right mouse buttons to rotate in different axes. Click
on the x, y, and z icons to enable rotation on an individual axis, or Ctrl+click
to toggle-select axes.
To translate components and clusters
To translate by dragging the mouse, click the translate (t) button. Alternatively,
quickly press and release the v key to activate the Translate tool in sticky mode,
or press and hold the v key while dragging to translate in supra mode.
Use the left, middle, and right mouse buttons to translate in different axes.
Click on the x, y, and z icons to enable translation on an individual axis, or
Ctrl+click to toggle-select axes.
You can also translate individual points with the Move Point tool.
34 • SOFTIMAGE|XSI
Working with Components
Transformation Modes
The buttons below the SRT boxes on the Transform panel control the
reference axes for transformations.
• Global transformations are performed along the scene’s global axes.
• Local transformations are performed along the components’ or clusters’
own reference axes. To display these axes, see Cluster Reference Frames on
page 35.
• View transformations are performed with respect to the viewing plane of
the viewport.
• Object transformations are performed in the local coordinate system of
the parent object. To display these axes, make sure that Show > Centers is
on in a viewport.
Each transformation tool has its own “memory.” When you activate a
transformation tool, the last mode is automatically selected.
Cluster Reference Frames
The cluster reference frame is the coordinate system that is used when
transforming components or clusters in Local mode. It acts like a center for
the selected clusters or components and defines the reference axes when you
transform clusters in Local mode. When multiple components are selected,
the average reference frame is used.
Selected polygons always share a reference frame, even if they are
not adjacent.
To display cluster reference frames
1. Do one of the following:
Cluster reference frame of
selected polygon
- To display cluster reference frames in a single viewport, choose Show >
Visibility Options in that viewport’s menu bar.
or
- To display cluster reference frames in all viewports, choose View >
Visibility Options (All Views) from the main-menu bar.
2. On the Attributes page of the Visibility Settings property editor, set
the following:
- Cluster Reference Frame—displays an axis indicator for the selected
clusters or components.
- Cluster Reference Frame Info—displays the XYZ position of the
reference frame.
Modeling & Deformations • 35
Chapter 1 • Basic Modeling
Cluster Centers
If you want more control over the center used for transforming components,
create a cluster and apply a cluster center deformation. For more information,
see Deforming by Cluster Centers on page 144.
Deforming
Components
36 • SOFTIMAGE|XSI
You can apply deformations to selected components and clusters in the same
way that you apply them to objects. See Chapter 6: Introduction to
Deformations on page 119 for general information about deformations, and
see other chapters in this guide for information about specific deformations.
Chapter 2
Polygons & Polygon Meshes
Modeling & Deformations • 37
Chapter 2 • Polygons & Polygon Meshes
38 • SOFTIMAGE|XSI
A polygon is a closed 2D shape formed by straight line segments that meet at
points called vertices. There are exactly the same number of vertex points as
line segments, and the line segments do not intersect anywhere else. The
simplest polygon is a triangle.
Approximating a smooth object surface from straight lines depends on the
number of polygons defined and also on the treatment of the surface normals
during the rendering process.
Each polygon on the object may or may not be planar (flat). As you move
vertices around in 3D space, you can make polygons non-planar. However,
when objects are automatically triangulated for rendering, non-planar
polygons are divided into triangles.
You can do most of your polygon modeling in SOFTIMAGE|3D and
import your objects into SOFTIMAGE|XSI for animation,
texturing, and rendering.
Modeling & Deformations • 39
Chapter 2 • Polygons & Polygon Meshes
Creating Polygon Meshes
There are two ways of creating polygon meshes:
• Choose a predefined item from the Get > Primitive > Polygon Mesh
menu on the Model toolbar.
or
• Import a polygon mesh object from SOFTIMAGE|3D.
Getting Primitive
Polygon Meshes
To get one of the primitive polygon meshes:
1. Choose Get > Primitive > Polygon Mesh, then choose a shape. The
corresponding property editor opens.
2. Set the parameters as desired:
- The shape-specific page contains the basic characteristics of the shape.
Each shape has different characteristics: for example, a sphere has only a
radius but a cylinder has both a radius and a height.
- The Geometry page controls how the implicit shape is subdivided when
converted into polygons. More subdivisions yield more points and
polygons, resulting in greater detail but heavier geometry.
Importing
Polygon Meshes
40 • SOFTIMAGE|XSI
You can import models and scenes with polygon objects from
SOFTIMAGE|3D. For more information see Importing Scenes in Chapter 3 of
the Fundamentals guide.
Working with Polygon-Mesh Components
Working with Polygon-Mesh Components
Polygon meshes are composed of several different types of component. Using
the filters on the Selection panel, you can select and work with each
component type:
• Points are the vertices of the polygons. Each point can be shared by many
adjacent polygons in the same mesh.
• Edges are the straight line segments joining two adjacent points. Edges can
be shared by at most two polygons. Edges that are not shared represent the
boundary of the polygon-mesh object.
• Polygons are the closed flat shapes that make up the “tiles” of the mesh.
Polygon
Edge
Point
Samples and polynodes will be available in a future release.
Modeling & Deformations • 41
Chapter 2 • Polygons & Polygon Meshes
Working with Points
You can modify polygon-mesh objects by moving points, as well as by
selecting points or point clusters then transforming them as described in
Transforming Components and Clusters on page 34. You can also apply
deformations to selected points and clusters in the same way that you apply
them to objects; see Chapter 6: Introduction to Deformations on page 119 for
general information about deformations, and other chapters for information
about specific deformations.
You cannot add or delete points on polygon-mesh objects.
Selecting Points
You can select (or tag) points, add and remove points from the selection, and
select point clusters using the selection filters in the main command area or
shortcut keys. For more information about selecting in general, see Selecting
and Deselecting Objects in Chapter 5 of the Fundamentals guide.
To select points
Choose the Point selection filter on the Selection panel and drag across points
in a viewport.
Alternatively, quickly press and release the t key to activate point selection in
sticky mode, or press and hold the t key while dragging to select points in
supra mode.
Selected points are displayed in red.
To extend the selection
If both the SI3D Selection Model and Extended Component Selection
options are off in the Selection menu, use modifier keys to add or remove
points from the selection:
• Shift+drag to select additional points.
• Ctrl+drag to toggle-select points.
• Ctrl+Shift+drag to deselect points.
If either SI3D Selection Model or Extended Component Selection are on, use
the different mouse buttons to add or remove points from the selection:
• Left-click to select additional points.
• Middle-click to toggle-select points.
• Right-click to deselect points.
42 • SOFTIMAGE|XSI
Working with Polygon-Mesh Components
To select clusters
Activate point selection using either the Point selection filter button or the t
key, then choose the Group/Cluster (+) selection filter in the Selection panel
and drag to select any point in the cluster.
Alternatively, if both the SI3D Selection Model and Extended Component
Selection options are off in the Selection menu, activate point selection and
middle-click to select any point in the cluster.
Selected clusters are displayed in white.
Using the Move Point Tool
As an alternative to selecting and translating points, you can move points
individually using the Move Point tool:
1. Select a polygon-mesh object.
2. Do one of the following:
- Choose Modify > Component > Move Point tool from the Model toolbar.
or
- Quickly press and release the m key to activate the Move Point tool in
sticky mode.
or
- Press and hold the m key move points in supra mode.
3. In a viewport, position the mouse pointer over a point on the object, then
click and drag to move it.
The Move Point tool has its own transformation mode “memory.” See
Transformation Modes on page 35.
Using Proportional Modeling
When you move or transform points and point clusters, you can use
proportional modeling. When this option is on, neighboring points are
moved as well, with a falloff that depends on distance. After you have moved
points, you can adjust the proportional settings.
To activate proportional modeling
On the Model toolbar, choose Modify > Component > Proportional. When
this option is on, neighboring points are affected any time you move or
transform points and point clusters.
To deactivate proportional modeling, choose Modify > Component >
Proportional to remove the check mark.
Modeling & Deformations • 43
Chapter 2 • Polygons & Polygon Meshes
To adjust proportional settings
1. Select the object.
2. Do one of the following:
- Choose Edit > Modeling Properties from the Edit panel and click the
Proportional tab. There is one Proportional property page for each
MovePoint operation with proportional on.
or
- Choose Property on the Selection panel, expand a MovePoint node, and
click the Proportional icon.
3. Adjust the parameters. Click the help icon for details.
Proportional modeling off
Working with Edges
Proportional modeling
using default profile
Proportional modeling
using modified profile
You can select edges and edge clusters, then transform them as described in
Transforming Components and Clusters on page 34. You can also apply
deformations to selected edges and clusters in the same way that you apply
them to objects; see Chapter 6: Introduction to Deformations on page 119 for
general information about deformations, and other chapters for information
about specific deformations.
You cannot add or delete edges on polygon-mesh objects.
Selecting Edges
You can select (or tag) edges, add and remove edges from the selection, and
select edge clusters using the selection filters in the Selection panel or shortcut
keys. For more information about selecting in general, see Selecting and
Deselecting Objects in Chapter 5 of the Fundamentals guide.
To select edges
Choose the Edge selection filter on the Selection panel in or press F10, then
drag across edges in a viewport.
Selected edges are displayed in red.
44 • SOFTIMAGE|XSI
Working with Polygon-Mesh Components
To extend the selection
If both the SI3D Selection Model and Extended Component Selection
options are off in the Selection menu in the Selection panel, use modifier keys
to add or remove edges from the selection:
• Shift+drag to select additional edges.
• Ctrl+drag to toggle-select edges.
• Ctrl+Shift+drag to deselect edges.
If either SI3D Selection Model or Extended Component Selection are on, use
the different mouse buttons to add or remove edges from the selection:
• Left-click to select additional edges.
• Middle-click to toggle-select edges.
• Right-click to deselect edges.
To select clusters
Activate edge selection using either the Edge selection filter button in or the
F10 key, then choose the Group/Cluster (+) selection filter in the Selection
panel and drag to select any edge in the cluster.
Alternatively, if both the SI3D Selection Model and Extended Component
Selection options are off in the Selection menu, activate edge selection and
middle-click to select any edge in the cluster.
Selected clusters are displayed in white.
Working
with Polygons
You can select polygons and polygon clusters, then transform them as
described in Transforming Components and Clusters on page 34. You can also
apply deformations to selected polygons and clusters in the same way that you
apply them to objects; see Chapter 6: Introduction to Deformations on
page 119 for general information about deformations, and see other chapters
for information about specific deformations. In addition, you can apply local
materials and textures to polygons.
• You cannot add or delete polygons on polygon-mesh objects.
• You cannot invert polygons.
• You cannot duplicate or extrude polygons.
Modeling & Deformations • 45
Chapter 2 • Polygons & Polygon Meshes
Selecting Polygons
You can select (or tag) polygons, add and remove points from the selection,
and select polygon clusters using the selection filters in the Selection panel or
shortcut keys.
The technique for selecting polygons depends on which selection tool you
are using:
• With the Rectangle, Lasso, and Paint Selection tools, you must include all
of a polygon’s vertex points to select it.
• With the Free Form Selection tool, you need only draw anywhere in the
interior of a polygon to select it. Like the Lasso tool, this tool works only
in wireframe views.
For more information about selecting in general, see Selecting and Deselecting
Objects in Chapter 5 of the Fundamentals guide.
Selected polygons always share a reference frame, even if they are
not adjacent.
To select polygons
Choose the Polygon selection filter on the Selection panel then drag across
polygons in a viewport.
Alternatively, quickly press and release the y key to activate polygon selection
in sticky mode, or press and hold the y key while dragging to select polygons
in supra mode.
Selected polygons are displayed in pink.
To extend the selection
If both the SI3D Selection Model and Extended Component Selection
options are off in the Selection menu, use modifier keys to add or remove
polygons from the selection:
• Shift+drag to select additional polygons.
• Ctrl+ctrl+drag to toggle-select polygons.
• Ctrl+Shift+drag to deselect polygons.
If either SI3D Selection Model or Extended Component Selection are on, use
the different mouse buttons to add or remove polygons from the selection:
• Left-click to select additional polygons.
• Middle-click to toggle-select polygons.
• Right-click to deselect polygons.
46 • SOFTIMAGE|XSI
Working with Polygon-Mesh Components
To select clusters
Activate polygon selection using either the Polygon selection filter button or
the y key, then choose the Group/Cluster (+) selection filter in the Selection
panel and drag to select any point in the cluster.
Alternatively, if both the SI3D Selection Model and Extended Component
Selection options are off in the Selection menu, activate polygon selection and
middle-click to select any polygon in the cluster.
Selected clusters are displayed in gray.
Applying Local Materials and Textures
You can apply materials and textures locally to selected polygons on a polygonmesh object. This allows you to put different materials and textures on different
polygons. For more information, see Applying a Local Material and Applying a
Local Texture in Chapter 3 of the Shaders, Lights & Cameras guide.
Modeling & Deformations • 47
Chapter 2 • Polygons & Polygon Meshes
Geometric Approximation on Polygon Meshes
You can control how polygon meshes are rendered by setting the geometry
approximation parameters. By default, there is one geometric approximation
property that is shared by all objects in the scene. You can modify the shared
property, or add a local property on the selected objects.
In addition, you can apply geometric approximation properties to groups and
layers, as well as use them in overrides.
In the Geometry Approximation property editor, only the options on the
Polygon Mesh and Displacement pages apply to polygon mesh objects.
To display shared geometric approximation properties
1. Select an object with a shared geometric approximation property.
2. Do one of the following:
- Choose Edit > Viewing Properties then click on the Geometry
Approximation tab. This tab is italicized if the property is shared.
or
- Click Property on the Selection panel, then click the Geometry
Approximation icon. When you are asked whether you want to create a
local copy, click No.
To create a local geometric approximation property
1. Select an element.
2. Do one of the following:
- Choose Get > Property > Geometry Approximation from a toolbar.
or
- Click Property on the Selection panel, then click the Geometry
Approximation icon. When you are asked whether you want to create a
local copy, click Yes.
48 • SOFTIMAGE|XSI
Geometric Approximation on Polygon Meshes
Faceted and
Smooth Polygons
The options on the Polygon Mesh page of the Geometry Approximation
property editor control whether the objects are faceted or smooth at the edges.
Faceted polygons are
appropriate for geometric
shapes like dice.
Faceted
Smooth
Smooth polygons are
appropriate for organic
shapes like faces.
By default, the illusion of smoothness is created by averaging the normals of
adjacent polygons if the angle between them (dihedral angle) is less than
60 degrees. At greater angles, no averaging occurs and the discontinuity
results in a faceted edge.
To change the threshold angle for faceted edges, make sure that Automatic
Discontinuity is on and adjust the Discontinuity Angle. For a completely
faceted object, set it to 0.
For a completely smooth object, turn off Automatic Discontinuity.
For a description of the other parameters, click for ? for Online Help.
Modeling & Deformations • 49
Chapter 2 • Polygons & Polygon Meshes
Setting an Automatic Discontinuity of 60 degrees smooths the edge on the left (< 60°)
but not the edge on the right (> 60°).
There is no option to keep exactly computed normals.
Displacement Mapping
The options on the Displacement page of the Geometry Approximation
property editor are used when you apply displacement maps. For more
information, see Creating a Displacement Map in Chapter 4 of the Shaders,
Lights & Cameras guide.
If you have set surface approximation options for a polygon-mesh
object in SOFTIMAGE|3D, they are translated into the corresponding options on the Displacement page when you import the object
into SOFTIMAGE|XSI.
50 • SOFTIMAGE|XSI
Chapter 3
Curves
Modeling & Deformations • 51
Chapter 3 • Curves
52 • SOFTIMAGE|XSI
In SOFTIMAGE|XSI, curves are linear (degree 1) or cubic (degree 3) NURBS
(non-uniform rational B-splines). NURBS are a class of curves that are easily
manipulated by computers, allowing for a great deal of flexibility in modeling.
Curves cannot be rendered because they have length but no width. Instead,
you can use curves to build surfaces as described in Chapter 4: Surfaces on
page 73. You can also use curves to control deformations as described in
Deforming by Curves on page 150 and Deforming by Spines on page 157. In
addition, you can use curves as paths and trajectories for animation as
described in Chapter 3: Animating along Paths and Trajectories in the
Animating guide.
Types of Curves
SOFTIMAGE|XSI lets you create two types of NURBS curve:
• Linear—straight line segments joined at the control points. Linear curves
have positional continuity (also known as C0, degree 0, or zero-order
continuity); this means that although the curve is connected, it is not
necessarily smooth. At least two control points are required to define a
linear curve.
• Cubic—smooth curves that are interpolated between the control points.
Cubic curves have curvature continuity (also known as C2, degree 2, or
second-order continuity); this means that there are no abrupt changes in
the position, tangent, or curvature along the curve—in other words, the
curve is very smooth. At least four control points are required to define a
cubic curve.
Linear NURBS curve
Cubic NURBS curve
You can import quadratic NURBS curves from SOFTIMAGE|3D.
Other types of curves—Bézier, Cardinal, and B-Spline—are
converted to cubic NURBS when imported. Clusters are lost
during conversion.
Modeling & Deformations • 53
Chapter 3 • Curves
Curve Components
and Attributes
Curves have many components and attributes which you can display with the
options on the Show menu in viewports.
Knots lie on the curve.
Boundary flags
show the
beginning of the
curve (U = 0).
Cubic curves are
interpolated
between points.
Segments are
the span
between knots.
Lines join points.
Points
Points, sometimes called control points or CVs (control vertices), define the
curve mathematically.
In linear curves, the points lie on the curve itself. At least two points are
required to define a linear curve.
In cubic curves, the curve is interpolated between the points. At least four
points are required to define a cubic curve.
You can modify curves by moving, adding, and deleting points. See Chapter 3:
Curves on page 69 for more information.
To display points, make sure that Show > Points is on in a viewport (or
View > Points to set all viewports at once). Alternatively, choose Show >
Visibility Options in a viewport (or View > Visibility Options to set all
viewports at once), then turn on the Points option on the Components page.
You can display points for selected objects, unselected objects, or both. Note
that the Show > Points option is automatically turned on whenever you
select, move, add, or delete points.
54 • SOFTIMAGE|XSI
Knots
Knots are the points at which curve segments meet. Each curve is actually a
series of connected segments, and every set of four consecutive points defines
a segment.
To display knots, choose Show > Knots in a viewport (or View > Knots to set
all viewports at once). Alternatively, choose Show > Visibility Options in a
viewport (or View > Visibility Options to set all viewports at once), then turn
on the Knots option on the Components page. You can display knots for
selected objects, unselected objects, or both.
You cannot manipulate knots directly.
Segments
Segments are spans of a curve between consecutive knots. For display
purposes, they are subdivided approximated by several straight line segments.
To specify how many straight line segments are used, set the Curve Step
option on the Hardware Display page of the Geometry Approximation
property editor. Note that this setting affects only the display; for example,
objects on paths will follow the curve as mathematically defined, not as
displayed. For more information about geometry approximation in general,
see Geometric Approximation Parameters on page 27.
Lines
Lines, sometimes called hulls, join consecutive points. When working with
curves and surfaces, it is sometimes useful to display them: turn on Show >
Lines in a viewport (or View > Lines to set all viewports at once).
Alternatively, choose Show > Visibility Options in a viewport (or View >
Visibility Options to set all viewports at once), then turn on the NURBS
Lines option on the Attributes page. You can display lines for selected objects,
unselected objects, or both.
Boundary Flags
Any point along a curve can be defined in terms of a single parameter U. You
can display boundary flags (also called edge flags) to show the beginning
(U = 0) of a curve: turn on Show > Boundaries in a viewport (or View >
Boundaries to set all viewports at once).
Alternatively, choose Show > Visibility Options in a viewport (or View >
Visibility Options to set all viewports at once), then turn on the Boundary
Flags option on the Attributes page. You can display boundaries for selected
objects, unselected objects, or both. The U = 0 boundary of a curve is shown
in red.
Other Components
Samples and isopoints will be available in a future version.
Modeling & Deformations • 55
Chapter 3 • Curves
Parameterization
Curves have a single parameter, U, along their length. Depending on how the
curve is parameterized, different values of U correspond to different points
along the length of the curve. You can reparameterize a curve as described in
Reparameterizing Curves on page 67.
Multiknots
If you add multiple control points at the same position, you create
multiknots—two or more overlapping knots. These let you create sharp
discontinuities on cubic curves. You can use grid snapping to add points at the
same position.
Single control point
56 • SOFTIMAGE|XSI
Two overlapping
control points
Three overlapping
control points
Creating Curves
Creating Curves
You can create a curve in several ways:
• By getting one of the predefined primitive curves, such as an arc or a spiral.
• By drawing a curve.
• By creating a curve from other objects in your scene. For example, you can
extract a portion of another curve, extract a curve from a surface, or
extract the intersection of two surfaces as a curve.
Primitive Curves
There are four types of primitive curve: arcs, circles, spirals, and squares. To
get a primitive curve:
1. Choose Get > Primitive > Curve, then choose a shape. The corresponding
property editor opens.
2. Set the parameters as desired:
- The shape-specific page contains the basic characteristics of the shape.
Each shape has different characteristics; for example, a square has only a
length but an arc has a radius, start angle, and end angle.
- The Geometry page controls how the implicit shape is subdivided when
converted into a curve. More subdivisions yield more points, resulting
in greater detail but heavier geometry.
Once you have added a primitive curve to your scene, you can modify it like
any other.
Drawing Curves
You can draw cubic curves in several different ways:
• By placing the control points explicitly. The curve is interpolated between
them. This is the traditional way to draw NURBS curves.
• By specifying the points that you want the curve to pass through.
SOFTIMAGE|XSI automatically adjusts the control points so that the
curve always passes through the points you pick.
• By clicking and dragging continuously as if you were sketching with a pen.
When you release the mouse button, SOFTIMAGE|XSI creates a curve
that approximates what you sketched.
There is only one way to draw linear curves: by adding points at the locations
where you want the straight segments to meet.
When drawing curves, grid snapping can be very useful for controlling the
position of points. See Grid Display and Snapping on page 28 for more
information.
Modeling & Deformations • 57
Chapter 3 • Curves
You should always draw curves in a counter-clockwise direction.
This ensures that the normals of any surfaces you create from the
curves will be oriented correctly.
Drawing Curves by Placing Control Points
To explicitly place control points and have a cubic curve pass between them:
1. Choose Create > Curve > Draw CV NURBS on the Model or Animate
toolbar. The mouse pointer changes to a pen.
2. Click in any geometry view to add the first point. Before you release the
mouse button, you can drag the mouse to adjust the point’s location.
3. Continue clicking to add more points.
- Left-click to add a point at the end of the curve.
- Middle-click to add a point in between two others on the curve.
- Right-click to add a point at the beginning of the curve.
You may be surprised that a curve is drawn after the second point,
even though it takes four points to define a cubic curve segment.
This is because points are automatically being automatically so that
there are always at least four. When you place the second point, three
are added. When you place the third point, the extra points are
removed and two are added at the third location. After you add the
fourth point, there are no extra points.
4. When you have finished drawing, exit the curve tool by choosing another
tool or pressing the Esc key. Alternatively, if you want to draw another
curve right away, middle-click on Create > Curve.
Drawing Curves by Placing Points on the Curve
To draw a curve by specifying the locations through which it should pass:
1. Choose Create > Curve > Draw Interpolating NURBS on the Model or
Animate toolbar. The mouse pointer changes to a pen.
2. Click in any geometry view to add the first point. Before you release the
mouse button, you can drag the mouse to adjust the point’s location.
3. Continue clicking to add more points.
- Left-click to add a point at the end of the curve.
- Middle-click to add a point in between two others on the curve.
- Right-click to add a point at the beginning of the curve.
4. When you have finished drawing, exit the curve tool by choosing another
tool or pressing the Esc key. Alternatively, if you want to draw another
curve right away, middle-click on Create > Curve.
58 • SOFTIMAGE|XSI
Creating Curves
Sketching Curves
You can draw a cubic curve by dragging the mouse freehand as if it were a pen:
1. Choose Create > Curve > Sketch on the Model or Animate toolbar. The
mouse pointer changes to a pen.
2. Click in any geometry view and drag the mouse freehand.
3. Release the mouse button to create the curve. The sketch tool remains
active and you can continue to draw more curves.
You can use Create > Curve > Fit on Curve to resample a sketched
curve. See Fitting Curves onto Curves on page 61 for more information.
Drawing Linear Curves
To draw a linear curve:
1. Choose Create > Curve > Linear on the Model or Animate toolbar. The
mouse pointer changes to a pen.
2. Click in any geometry view to add the first point. Before you release the
mouse button, you can drag the mouse to adjust the point’s location.
3. Continue clicking to add more points.
- Left-click to add a point at the end of the curve.
- Middle-click to add a point in between two others on the curve.
- Right-click to add a point at the beginning of the curve.
4. When you have finished drawing, exit the curve tool by choosing another
tool or pressing the Esc key. Alternatively, if you want to draw another
curve right away, middle-click on Create > Curve.
Creating Curves
from Other Objects
You can use other objects in your scene to create curves. For example, you can:
• Extract an arbitrary segment of an existing curve.
• Extract a curve from a surface.
• Fit a curve onto another curve.
• Create a curve from the intersection of two surfaces.
• Blend two curves; that is, create a third joining curve between them.
• Create a fillet between two intersecting curves.
• Merge two curves; that is, create a curve that spans the originals.
• Generate a curve from the animated translation of an object.
Modeling & Deformations • 59
Chapter 3 • Curves
In each case except the last, a modeling relation exists between the new curve
and the original objects used to define it. Modifying the originals in any way
also modifies the created curve. In addition, you can select the created curve
and open the property editor of the corresponding operator to adjust its
parameters. The modeling relation exists until you select the created curve
and choose Edit > Freeze Operator Stack from the Edit panel.
If you delete the input objects without freezing the operator stack of
the output object first, the output object is removed from the scene.
See Freezing the Operator Stack on page 30.
If this happens accidentally, press Ctrl+z to undo.
To extract an arbitrary segment of an existing curve
1. Select the curve in Object mode.
2. Choose Create > Curve > Extract Segment from the Model toolbar. A
new curve is created corresponding to the total length of the original
curve, and the Extract Curve Segment property editor opens.
3. Adjust the Start Position and End Position parameters to the define the
segment you want to extract.
Original curve
Extracted segment
To extract a curve from a surface
1. Select the surface in Object mode.
2. Choose Create > Curve > Extract from Surface from the Model toolbar. A
curve is created on the surface and the Extract Curve property editor
opens.
3. Adjust the parameters to define the curve you want to extract.
Extracting a curve
from a surface
60 • SOFTIMAGE|XSI
Creating Curves
Fitting Curves onto Curves
You can fit one curve onto another. This is useful for cleaning curves that were
drawn with the Sketch tool. You can specify the number of points and the
degree of the new curve.
Original sketched curve
New curve fitted onto sketched curve
To fit one curve onto another
1. Select a curve in Object mode.
2. Choose Create > Curve > Fit on Curve from the Model toolbar. A new
curve is created and the Fit Curve property editor opens.
3. Set values as desired:
- Number of Points controls the number of control points on the created
curve and, indirectly, how accurately the new curve follows the original.
- Continuity controls the smoothness of the curve. Choose Position (C0,
or linear), Tangent (C1, or quadratic), or Curvature (C2, or cubic).
- Close does not create a true periodic curve; instead, it superimposes the
last point on the first.
Intersecting Surfaces
You can create a curve that represents the intersection of two surfaces. For best
results, first make sure that the surfaces have the same parameterization; see
Chapter 4: Surfaces on page 93.
Intersection between
two surfaces
1. Select one of the surfaces in Object mode.
Modeling & Deformations • 61
Chapter 3 • Curves
2. Choose Create > Curve > Intersect Surfaces from the Model toolbar.
3. Pick the other surface. A curve is created and the Intersect Surfaces
property editor opens.
If you change your mind, press the Esc key to cancel the operation without
picking anything.
If the two surfaces intersect in multiple places, the new curve will be
composed of multiple disjoint segments. However, the curve is one
single 3D object as shown in the explorer.
4. You may need to adjust the tolerance parameters for the curve.
Blending Curves
Blending two curves creates a third curve that joins the two originals.
Original curves
New blend curve
1. Select the first curve in Object mode.
2. Choose Create > Curve > Blend from the Model toolbar.
3. Pick the other curve. A third curve is created and the Blend Curves
property editor opens.
If you change your mind, press the Esc key to cancel the operation without
picking anything.
4. Depending on how you drew the original curves, you may need to adjust
the parameters for the blended curve.
As an alternative to blending curves, you can merge them as described on
page 64 or stitch them as described on page 68.
62 • SOFTIMAGE|XSI
Creating Curves
Filleting Curves
You can create a curve that is a fillet, or smooth blending arc, between two
curves. Depending on how the curves are drawn and the options you set, the
two original curves do not need to intersect.
Intersecting curves
Fillet between them
1. Select the first curve in Object mode.
2. Choose Create > Curve > Fillet Intersection from the Model toolbar.
3. Select the second curve.
If you change your mind, press the Esc key to cancel the operation without
picking anything.
4. An arc is drawn from the beginning of the first curve to the end of the
second, and the Fillet Curves property editor appears.
If the two curves intersect in multiple places, the new curve will be
composed of multiple disjoint segments. However, the curve is one
single 3D object as shown in the explorer.
5. Adjust the Radius and the Tolerance. If no fillet can be created with the
specified settings, a unit circle is created at the origin.
To change where the fillet is created on the crossing curves, invert
one or both curves using Modify > Curve > Inverse.
For a non-circular fillet, you can move points or otherwise deform
the created curve. The modeling relation with the original curve
remains, so that if you modify the original curves the deformed fillet
changes accordingly.
As an alternative to filleting curves, you can blend curves as described in the
previous section, or merge them as described in the next section.
Modeling & Deformations • 63
Chapter 3 • Curves
Merging Curves
Merging two curves creates a third curve that spans the original two.
Two separate curves
Single merged curve
1. Select the first curve in Object mode.
2. Choose Create > Curve > Merge from the Model toolbar.
3. Pick the other curve. A third curve is created as if the first point of the
second curve was superimposed on the last point of the first curve, and
the Merge Curves Together property editor opens.
If you change your mind, press the Esc key to cancel the operation without
picking anything.
4. If necessary, adjust the parameters of the merged curve. Click the help
icon for more information.
As an alternative to merging curves, you can also or stitch them as described
on page 68 or blend them as described on page 62.
Creating Curves from Animation
If you have animated the translation of an object, you can plot the motion of
its center to generate a curve. For example, this can be used to create a
trajectory curve. You can also plot the movement of a selected point or cluster,
similar to the Tag2Path command in SOFTIMAGE|3D.
1. Select an object, point, or cluster.
2. Choose Tools > Plot > Curve from the Animate toolbar.
3. When prompted, set the start frame and click OK.
4. When prompted, set the end frame and click OK.
A curve is created, with one control point for every frame. The original
animation remains.
64 • SOFTIMAGE|XSI
Modifying Curves
Modifying Curves
You can modify curves in a variety of ways using the commands in the
Modify > Curve menu of the Model toolbar. The Add Point Tool and Delete
Point Tool are described in Adding and Deleting Points on page 71.
All of the commands in the Modify > Curve menu change the curve’s
underlying topology. Topological changes are always evaluated before
any deformations, even if you applied the deformations first. If you
don’t get the results you want, try freezing the curve’s operator stack as
described in Freezing the Operator Stack on page 30.
Inverting Curves
Inverting a curve reverses its parameterization so that U increases in the
opposite direction. The result is as if you had drawn the curve clockwise
instead of counter-clockwise, or vice versa. For example, if an object uses the
curve as a path, it moves in the opposite direction once you invert the curve.
Similarly, if a surface has been built from the curve and its operator stack was
not frozen, its normals become reversed.
To invert curves:
1. Select one or more curves in Object mode.
2. Choose Modify > Curve > Inverse from the Model toolbar.
Reinverting Curves
If you later decide that you no longer want the curve inverted, you can do one
of three things:
• Select the curve and choose Edit > Modeling Properties, then uncheck the
Inverse Curve parameter on the Inverse Curve page. Later operations in
the stack may be affected.
or
• Use an explorer view to expand the curve’s node and delete the Inverse
Curve operator. Later operations in the stack may be affected.
or
• Select the curve and choose Modify > Curve > Inverse again. This adds
another Inverse Curve node to the operator stack and may result in
unnecessary calculations.
Modeling & Deformations • 65
Chapter 3 • Curves
Opening and Closing
Curves
You can open a closed curve, and close an open curve. Curves are always
opened at the U = 0) position.
1. Select one or more curves in Object mode.
2. Choose Modify > Curve > Open/Close. The curve is opened if it were
closed, and closed if open.
Open curve
Closed curve
Reopening and Reclosing Curves
If you later decide that you no longer want the curve to be open (or closed),
you can do one of two things:
• Select the curve and choose Modify > Curve > Open/Close again. This
adds another Open/Close Curve node to the operator stack and may result
in unnecessary calculations.
or
• Use an explorer view to expand the curve’s node and delete the
Open/Close Curve operator. Later operations in the stack may be affected.
Shifting U on Curves
On closed curves, you can shift the start point (U = 0 position) along the
length of the curve.
1. Select one or more curves in Object mode.
2. Choose Modify > Curve > Shift U. The Curve Shift property editor opens.
3. Adjust the Shift U parameter. As you change values, the start point jumps
to the nearest knot.
Cleaning Curves
Cleaning a curve reduces the number of control points while keeping the
same general shape.
1. Select one or more curves using the Object filter on the Selection panel.
2. Choose Modify > Curve > Clean from the Model toolbar. The Clean
Curve property editor opens.
3. Set the Tolerance. This controls the maximum difference between the
original curve and the resampled shape.
66 • SOFTIMAGE|XSI
Modifying Curves
Reparameterizing
Curves
Parameterization refers to the way that any point along the length of a curve is
described in terms of the parameter U. Any given point along the curve can
have different U values under different parameterizations.
The various parameterization methods can affect the curve’s behavior when you
perform certain operations. There are four parameterization methods available:
• With uniform parameterization, the difference between successive knots is
equal to 1 regardless of the actual length of the curve segment. (While it
may seem strange that non-uniform rational B-splines can have a uniform
parameterization, it is not a contradiction; “non-uniform” here means
“not necessarily uniform.”) Uniform parameterization is especially
suitable when merging and lofting.
• With non-uniform parameterization (the default), the difference between
successive knots is related to the length of each curve segment the first
time the curve is drawn. However, when you edit the curve, the
parameterization is not recomputed. Instead, the exact shape of your
curve is preserved. For this reason, you can manipulate curves with nonuniform parameterization more accurately.
• With chord length parameterization, the difference between successive
knot values is related to the actual length of each curve segment. If you
could see the knot values on the actual curve, these values might be
unequal: 1, 3.2, 5.3, and so on. Chord length always strives to preserve the
relation between the length of the curve segment and the spacing of the
knot vector. When you modify the curve, the parameterization of the
curve is completely recomputed to preserve the relation of length of
segment/knot spacing. As a result of this recomputation, when you move
a control point, the edited segment jumps to a slightly different position
when you release the mouse button.
• With centripetal parameterization, the knot spacing is related to the
square root of the length of each curve segment. In some cases, this may
make smoother curves. As with chord length parameterization, the
parameterization is completely recomputed when you move points, with
the result that the curve may jump when you release the mouse button.
To reparameterize curves
1. Select one or more curves in Object mode.
2. Choose Modify > Curve > Reparameterize from the Model toolbar. The
Reparameterize Curve property editor opens.
3. Choose a parameterization method.
Modeling & Deformations • 67
Chapter 3 • Curves
To reparameterize curves again
If you later decide to change the parameterization again, do one of the following:
• Select the curve and choose Edit > Modeling Properties, then click on the
Reparameterize Curve tab and choose a different option. The results of
later operators in the stack may be affected.
or
• Select the curve and choose Modify > Curve > Reparameterize again.
This adds another Reparameterize Curve node to the operator stack and
may cause unnecessary calculations.
or
• Use an explorer view to expand the curve’s node and delete the
Reparameterize Curve operator. This returns to the original
parameterization—later operators in the stack may be affected.
Stitching Curves
Stitching two curves glues their ends together. Unlike blending (page 62) or
merging (page 64), it does not create a new curve but instead distorts the
originals.
1. Select the first curve in Object mode.
2. Choose Modify > Curve > Stitch from the Model toolbar.
3. Pick the second curve. The Stitch Curves property editor opens.
If you change your mind, press the Esc key to cancel the operation without
picking anything.
4. Adjust the parameters to obtain the desired shape. Click the help icon for
more information.
68 • SOFTIMAGE|XSI
Working with Points
Working with Points
You can modify curves by moving points, as well as by selecting points or
point clusters then transforming them as described in Transforming
Components and Clusters on page 34. You can also apply deformations to
selected points and clusters in the same way that you apply them to objects;
see Chapter 6: Introduction to Deformations on page 119 for general
information about deformations, and see other chapters for information
about specific deformations. In addition, you can add and delete points as
described in Adding and Deleting Points on page 71.
Selecting Points
You can select (or tag) points, add and remove points from the selection, and
select point clusters using the selection filters in the Selection panel or using
shortcut keys. For more information about selecting in general, see Selecting
and Deselecting Objects in Chapter 5 of the Fundamentals guide.
To select points
Choose the Point selection filter on the Selection panel and drag across points
in a viewport.
Alternatively, quickly press and release the t key to activate point selection in
sticky mode, or press and hold the t key while dragging to select points in
supra mode.
Selected points are displayed in red.
To extend the selection
If both the SI3D Selection Model and Extended Component Selection
options are off in the Selection menu in the Selection panel, use modifier keys
to add or remove points from the selection:
• Shift+drag to select additional points.
• Ctrl+drag to toggle-select points.
• Ctrl+Shift+drag to deselect points.
If either SI3D Selection Model or Extended Component Selection are on, use
the different mouse buttons to add or remove points from the selection:
• Left-click to select additional points.
• Middle-click to toggle-select points.
• Right-click to deselect points.
Modeling & Deformations • 69
Chapter 3 • Curves
To select clusters
Activate point selection using either the Point selection filter button or the t
key, then choose the Group/Cluster (+) selection filter in the Selection panel
and drag to select any point in the cluster.
Alternatively, if both the SI3D Selection Model and Extended Component
Selection options are off in the Selection menu, activate point selection and
middle-click to select any point in the cluster.
Selected clusters are displayed in white.
Moving Points
As an alternative to selecting and translating points, you can move points
individually using the Move Point tool:
1. Select an object.
2. Do one of the following:
- Choose Modify > Component > Move Point tool from the Model toolbar.
or
- Quickly press and release the m key to activate the Move Point tool in
sticky mode.
or
- Press and hold the m key move points in supra mode.
3. In a viewport, position the mouse pointer over a point on the object, then
click and drag to move it.
The Move Point tool has its own transformation mode “memory.” See
Transformation Modes on page 35.
Using Proportional
Modeling
When you move or transform points and point clusters, you can use
proportional modeling. When this option is on, neighboring points are
moved as well, with a falloff that depends on distance. After you have moved
points, you can adjust the proportional settings.
To activate proportional modeling
On the Model toolbar, choose Modify > Component > Proportional. When
this option is on, neighboring points are affected any time you move or
transform points and point clusters.
To deactivate proportional modeling, choose Modify > Component >
Proportional to remove the check mark.
To adjust proportional settings
1. Select the object.
2. Do one of the following:
70 • SOFTIMAGE|XSI
Working with Points
- Choose Edit > Modeling Properties and click the Proportional tab.
There is one Proportional property page for each MovePoint operation
with Proportional on.
or
- Choose Property on the Selection panel, expand a MovePoint node, and
click the Proportional icon.
3. Adjust the parameters. Click the help icon for details.
Adding and Deleting
Points
You can add and delete points on curves.
When you add or delete points, you change the curve’s underlying
topology. Topological changes are always evaluated before any
deformations, even if you applied the deformations first. If you don’t
get the results you want, try freezing the curve’s operator stack as
described in Freezing the Operator Stack on page 30.
If you add points or knots to an object with clusters, the clusters
will shift.
To add points to an existing curve
1. Select a curve in Object mode.
2. Choose Modify > Curve > Add Point from the Model toolbar. The
pointer changes to a pen.
3. Click to add points, just as if you were drawing the curve:
- Left-click to add a point at the end of the curve.
- Middle-click to add a point in-between two others on the curve.
- Right-click to add a point at the beginning of the curve.
Before you release the mouse button, you can drag the mouse to adjust the
point’s location.
4. When you have finished drawing, exit the Add Point tool by choosing
another tool or pressing the Esc key.
If you want to add points to another curve, you must first select it and
choose Modify > Curve > Add Point again—if you don’t choose the
command again, the points are added to the previous curve. Note that you
can middle-click to quickly repeat the last command chosen from a
toolbar menu button.
Modeling & Deformations • 71
Chapter 3 • Curves
The mode in which you originally drew the curve is preserved until
you freeze it or apply a topology operator as described in Modifying
Curves on page 65. For example, if you add a point between two
others on a curve drawn with Draw CV NURBS, a control point is
added where you clicked and the curve is interpolated accordingly. If
you add a point to a curve drawn with Draw Interpolating NURBS,
a control point is added so that the curve passes through the
position you clicked.
After you freeze the curve or apply a topology operator, the curve
always passes through the position you clicked.
To delete points on a curve
1. Select a curve in Object mode.
2. Choose Modify > Curve > Delete Point from the Model toolbar.
3. Click on a point to delete it.
You can continue to click on other points to delete them. When you have
finished deleting points, exit the Delete Point tool by choosing another
tool or pressing the Esc key.
72 • SOFTIMAGE|XSI
Chapter 4
Surfaces
Modeling & Deformations • 73
Chapter 4 • Surfaces
74 • SOFTIMAGE|XSI
Surfaces are one of the basic types of renderable geometry in
SOFTIMAGE|XSI. Surfaces are typically smoother than polygon meshes, and
they’re ideal for organic and flexible shapes.
In SOFTIMAGE|XSI, surfaces are NURBS patches. Mathematically, they are
an interconnected patchwork of smaller surfaces defined by intersecting
NURBS curves.
Surfaces are the building blocks of surface meshes, described in Chapter 5:
Surface Meshes on page 103.
As you manipulate objects and play back animation, you may notice
that surface objects are displayed in coarse mode. This is an option
that allows for faster interaction. You can toggle this on or off by
choosing File > User Preferences from the main-menu bar then
choosing the Interaction tab and clicking Display Options Use
Coarse Step by Default for Interaction and Playback under Display
Performance. You must restart SOFTIMAGE|XSI before this change
takes effect.
You can also set the Step value to Coarse, Medium, or Full during
Interaction and Playback for Selected Objects and Unselected
Objects in individual viewports or all viewports at once. For more
information, see Setting Object Display in Chapter 4 of the
Fundamentals guide.
If you import a Cardinal, Bézier, or B-Spline patch object, it is
converted to a NURBS surface. Some things will be lost:
• Clusters, cluster animation, and cluster constraints will not be
included in the conversion.
• If the object is an envelope, the original weight assignment is
lost. To avoid this, convert patches to NURBS and use the Skin >
Weight Copy and Weight Paste commands before importing the
converted NURBS envelopes.
Surface UV
Parameterization
Surfaces have two parameters, U and V. In Wireframe view, surfaces are
represented by a grid of curves that intersect at points called knots. Each of
these curves is constant in either U or V. An arbitrary point on a surface can
be described in terms of its (U, V) coordinates.
Like curves, surfaces can be either cubic (second order, or C2) or linear (zero
order, or C0). In addition, they can have different orders in their U and V
directions, so that they can be smooth in one direction and jagged in the
other. You can reparameterize surfaces as described in Reparameterizing
Surfaces on page 93.
A surface can be open in both U and V like a grid, closed in both like a torus,
or open in one and closed in the other like a tube.
Modeling & Deformations • 75
Chapter 4 • Surfaces
U and V are similar to latitude and longitude.
Components
of Surfaces
Surfaces have many components: points, knots, boundaries, and isolines.
Points
Points are the control points of the curves that define the surface.
Points define
and control the
surface.
You can display
lines between
points.
You cannot add or remove points directly, but you can add and remove knots
as described in Working with Knots and Knot Curves on page 100—this has the
effect of adding or removing points indirectly.
To display points, make sure that Show > Points is on in a viewport (or
View > Points to set all viewports at once). Alternatively, choose Show >
Visibility Options in a viewport (or View > Visibility Options to set all
viewports at once), then turn on the Points option on the Components page.
You can display points for selected objects, unselected objects, or both. Note
that the Show > Points option is automatically turned on whenever you select
or move points.
76 • SOFTIMAGE|XSI
Lines
Lines, sometimes called hulls, join consecutive points. When working with
curves and surfaces, it is sometimes useful to display them: turn on Show >
Lines in a viewport (or View > Lines to set all viewports at once).
Alternatively, choose Show > Visibility Options in a viewport (or View >
Visibility Options to set all viewports at once), then turn on the NURBS
Lines option on the Attributes page. You can display lines for selected objects,
unselected objects, or both.
Knots and Knot Curves
Surface knots are the knots of the curves that define the surface; they lie on the
surface where the U and V curve segments meet. Knot curves are sets of
connected knots along U or V—they are the “wires” shown in wireframe
views. You can select knot curves and use them, for example, to build other
surfaces using the Loft operator. You can add and remove knots as described
in Working with Knots and Knot Curves on page 100.
Knots lie
on the surface.
Knot curves
connect knots.
To display knots, choose Show > Knots in a viewport (or View > Knots to set
all viewports at once). Alternatively, choose Show > Visibility Options in a
viewport (or View > Visibility Options to set all viewports at once), then turn
on the Knots option on the Components page. You can display knots for
selected objects, unselected objects, or both.
You cannot transform or deform knots directly.
Boundaries
The minimum and maximum U and V values define the boundaries of a
surface. On surfaces that are open in one or both directions, these are the
outer edges. You can use the Boundaries selection filter to help you pick
boundaries for lofting and other operations.
When working with surfaces, it may be helpful to display boundary flags (also
called edge flags). This shows the U = 0 boundary in red and the V = 0
boundary in green. Turn on Show > Boundaries in a viewport (or View >
Boundary to set all viewports at once).
Modeling & Deformations • 77
Chapter 4 • Surfaces
Alternatively, choose Show > Visibility Options in a viewport (or View >
Visibility Options to set all viewports at once), then turn on the Boundary
Flags option on the Attributes page. You can display boundaries for selected
objects, unselected objects, or both.
Isolines
Isolines are not true components. They are in fact arbitrary lines of constant
U or V on a surface . You can use the U and V Isoline selection filter to help
you pick isolines for lofting and other operations.
Isolines are arbitrary lines
on the surface in U or V.
Surface Curves and Trim Curves
You cannot create projected surface curves or trim curves in
SOFTIMAGE|XSI. However, you can import objects with projected surface
curves and trim curves from SOFTIMAGE|3D. In SOFTIMAGE|XSI, you can
select them using the Surface Curve and Trim Curve selection filters, then use
them for lofting and other operations.
Other Components
Samples and isopoints will be available in a future release.
Multiknot Curves
78 • SOFTIMAGE|XSI
Just like with multiknots on curves, you can add multiple knot curves at the
same position. This lets you create sharp ridges on surfaces. See Adding Knot
Curves on page 100.
Creating Surfaces
Creating Surfaces
There are two basic ways to create a surface:
• By getting one of the predefined primitive surfaces.
or
• By building a surface from curves or other objects in your scene. There are
several ways to do this.
Primitive Surfaces
There are several types of predefined primitive surfaces. To get a primitive surface:
1. Choose Get > Primitive > Surface then choose a shape. The
corresponding property editor opens.
2. Set the parameters as desired:
- The shape-specific page contains the basic characteristics of the shape.
Each shape has different characteristics; for example, a sphere has one
radius and a torus has two.
- The Geometry page controls how the implicit shape is subdivided when
converted into a surface. More subdivisions yield more points, resulting
in greater detail but heavier geometry.
Once you have added a primitive surface to your scene, you can modify it like
any other.
Modeling & Deformations • 79
Chapter 4 • Surfaces
Creating Surfaces
from Curves
You can create surfaces by first creating curves and using them as building
blocks. There are several ways to use curves to create surfaces:
• By extruding one curve along an axis or another curve.
• By extruding with two profiles, morphing one into the other as it runs
along a rail curve.
• By creating a series of profiles and lofting them.
• By revolving a curve around an axis or another curve.
• By extruding an open curve along two guides. (Birail)
• By picking a series of curves in U and V. (Curve Net)
• By picking the four curves to use as boundaries. (Four Sided)
In each case, a modeling relation exists between the surface and the curves
used to define it. Modifying the curves in any way also modifies the created
surface. In addition, you can select the surface and open the property editor of
the corresponding operator to adjust the parameters that control how the
surface is created. The modeling relation exists until you select the surface and
choose Edit > Freeze Operator Stack from the Edit panel.
If you delete the input objects without freezing the operator stack of
the output object first, the output object is removed from the scene.
See Freezing the Operator Stack on page 30.
If this happens accidentally, press Ctrl+z to undo.
The resulting surfaces can be linear or cubic in either U or V, depending on
whether the original curves are linear or cubic. Remember to draw curves
counter-clockwise for the proper alignment of normals. If the normals of the
resulting surface are pointing in the wrong direction, you can invert the
surface as described on page 91 or invert one or more of the input curves as
described on page 65.
80 • SOFTIMAGE|XSI
Creating Surfaces
Extruding Curves
You can create a surface by extruding a profile curve along an axis or a rail
curve. This and similar operations are sometimes called rail or sweep.
1. Select the profile curve.
2. Choose Create > Surface > Extrusion from the Model toolbar. If you
change your mind, press the Esc key to cancel the operation.
3. Do one of the following:
- Pick a guide curve to extrude along and then right-click.
or
- Right-click without picking anything to extrude along an axis.
The Extrude Curve property editor opens.
4. Adjust the parameters as desired:
- Specify the number of Subdivisions in U and V.
- Specify whether the surface should be open or closed in U and V.
- Specify the Start Position and Length along the curve or axis.
- Specify whether the surface should be created at the position of the
guide curve (Snap to Profile off) or the profile curve (on).
- Specify whether the profile should be rotated according to the tangency
of the guide curve (Rotate Profile).
- If you did not pick a guide curve, specify the axis to extrude along. You
can select a combination of axes to extrude along the resulting diagonal.
Profile curve
Guide curve
Extruded surface
Modeling & Deformations • 81
Chapter 4 • Surfaces
Extruding with Two Profiles
When you create a surface by extruding with two profiles, the first profile
morphs into the second profile as it runs along a single rail curve.
1. Create two profile curves and a rail curve. For best results, the first points
of the two profiles should be close to the endpoints of the rail. You can use
the Ctrl key to snap to the grid when adding or moving points.
2. Select the rail curve.
3. Choose Create > Surface > Extrusion - 2 Profiles from the Model toolbar.
If you change your mind, press the Esc key to cancel the operation.
4. Pick the first profile. If you made a mistake, Ctrl+click to unpick it.
5. Pick the second profile. The Extrusion 2 Profiles property editor opens.
6. Set the parameters:
- Adjust the Maximum Endpoint Gap, depending on how far apart the
endpoints of the profile are from the guide rails.
- Set the desired number of subdivisions in U and V.
Profile 2
Resulting surface
Guide curve
Profile 1
82 • SOFTIMAGE|XSI
Creating Surfaces
Lofting Curves
You can create a series of profile curves, then use the Loft command to create a
surface with the corresponding cross-sections. This procedure is sometimes
called skinning.
While lofting, you can use the selection filters in the Selection panel to pick any
combination of curve objects, knot curves, boundaries, isolines, surface curves,
and trim curves. For example, you can create a loft surface that joins two
surfaces while passing through other curves. You can also quickly create a low
resolution version of an object by picking isolines along its surface.
1. Select the first curve in the series. You can use the Selection filters to select a
boundary, isoline, or knot curve on a surface as well as an ordinary curve object.
2. Choose Create > Surface > Loft from the Model toolbar. If you change
your mind, press the Esc key to cancel the operation.
3. Pick each of the other profile curves in order. As you pick, you can change
the selection filters to pick any combination of boundaries, isolines, knot
curves, and object curves.
If you make a mistake, you can unpick curves in order using Ctrl+click.
You can also cancel the loft operation by pressing Esc.
• With the Free Form selection tool, you can pick curve objects in
a single sweep.
• To create a surface that is closed in U, repick the first curve as the
last curve.
Loft will not work if there are overlapping curves. If you created
curves by duplicating them, make sure that two or more don’t overlap.
4. Right-click to indicate that you have finished picking profile curves. The
Loft property editor opens.
5. Set the parameters as desired:
- Specify the number of Subdivisions in U and V.
- The Start and End Surface parameters are used only when the first and
last curves are on surfaces (boundaries, knot curves, or isolines). They
determine how the continuity of the loft surface matches that of the
input surfaces. For more information, click the help icon.
Modeling & Deformations • 83
Chapter 4 • Surfaces
Lofting curve objects
Lofting using mixed curves
Boundary
Curve
object
Isoline
Revolving Curves
You can create a surface by revolving a curve around an axis or around
another curve:
1. Select the curve to be revolved in Object mode.
2. Choose Create > Surface > Revolution from the Model toolbar. If you
change your mind, press the Esc key to cancel the operation.
3. Do one of the following:
- Pick a curve to revolve around and then right-click. The revolution
occurs around a straight line from the start to the endpoint of the curve
you pick.
or
84 • SOFTIMAGE|XSI
Creating Surfaces
- Right-click without picking anything to revolve around an axis.
The Revolution property editor opens.
4. Adjust the parameters as desired:
- Specify the number of Subdivisions in U and V.
- Specify whether the surface should be open or closed in U and V.
- Specify the angle at which to begin the revolution (Start Angle) and
number of degrees to sweep through (Revolution Angle).
- If you did not pick a curve to revolve around, specify the axis to extrude
along. You can select a combination of axes to revolve around the
resulting diagonal.
Revolution
Axis
Profile
Birail
The Birail operator lets you extrude an open-profile curve by running its endpoints
along two rails, or guide curves. This is sometimes called guided extrusion.
1. Create the profile curve and the two rail curves. For best results, make sure
that each endpoint of the profile is close to the start of the corresponding rail.
You can use the Ctrl key to snap to the grid when adding or moving points.
2. Select the profile curve, then choose Surface > Create > Birail from the Model
toolbar. If you change your mind, press the Esc key to cancel the operation.
3. Pick the first rail. If you make a mistake, you can unpick it with Ctrl+click.
4. Pick the second rail. The Birail property editor opens.
5. Set the parameters:
- Adjust the Maximum Endpoint Gap, depending on how far apart the
endpoints of the profile are from the guide rails.
- Set the desired number of subdivisions in U and V.
Modeling & Deformations • 85
Chapter 4 • Surfaces
Birail
Profile
Guide rails
Using Curve Net
You can create a surface by picking a series of curves in U and V. Curve Net is
similar to Loft, but you can control the detail in both the U and V directions.
1. Create two sets of curves, representing cross-sections in U and V. For best
results, make sure the curves intersect each other as closely as possible,
particularly at the boundaries.
2. Select the first U curve in Object mode.
3. Choose Create > Surface > Curve Net from the Model toolbar. If you
change your mind, press the Esc key to cancel the operation.
4. Pick the remaining U curves in order.
With the Free Form selection tool, you can pick the curves in a single
sweep. Be careful not to accidentally select a V curve.
If you make a mistake, Ctrl+click to “unpick” the last curve. Repeat
to “unpick” multiple curves.
5. Right-click to indicate that you have finished picking U curves.
6. Pick the V curves in order.
7. Right-click. The Curve Net property editor opens.
8. Adjust parameters as necessary:
- Specify the number of Subdivisions in U and V.
- Set Feature Match to follow the detail of the input curves more closely.
Note that this may significantly affect performance.
86 • SOFTIMAGE|XSI
Creating Surfaces
Picking Boundaries Using Four-Sided
You can create a simple surface by picking four curves to define the surface’s
boundaries:
1. Draw the four curves to serve as the boundaries. For best results, make
sure that their ends meet as closely as possible. You can use the Ctrl key to
snap to the grid when adding or moving points.
2. Select one of the curves in Object mode.
3. Choose Create > Surface > Four Sided from the Model toolbar. If you
change your mind, press the Esc key to cancel the operation.
4. Pick the remaining boundary curves in clockwise order. If you make a
mistake, Ctrl+click to unpick the last curve. When you pick the last one, the
surface is created immediately and the FourSided property editor opens.
5. Set the desired number of subdivisions in U and V.
Four Sided
Creating Surfaces
from Other Surfaces
You can create surfaces from other surfaces in several ways:
• You can create a third surface that fills the gap and blends between the
boundaries of two surfaces.
• You can create a fillet to smooth the intersection of two surfaces.
• You can create a merged surface that spans two others.
In each case, a modeling relation exists between the new surface and the
originals used to define it. Modifying the originals in any way also modifies the
created curve. In addition, you can select the created surface and open the
property editor of the corresponding operator to adjust the parameters that
control how the surface is created. The modeling relation exists until you select
the surface and choose Edit > Freeze Operator Stack from the Edit panel.
If you delete the input objects without freezing the operator stack of
the output object first, the output object is removed from the scene.
See Freezing the Operator Stack on page 30.
If this happens accidentally, press Ctrl+z to undo.
Modeling & Deformations • 87
Chapter 4 • Surfaces
Blending Surfaces
To create a surface that fills the gap and blends between two other surfaces:
1. Select one of the surfaces in Object mode.
2. Choose Create > Surface > Blend from the Model toolbar. If you change
your mind, press the Esc key to cancel the operation.
3. Pick the other surface. A blend is created and the Blend Surfaces property
editor opens.
4. Set the options as desired:
- If the blend was not created between the boundaries you wanted, use the
options on the Boundaries page to specify which boundaries of the
original surfaces to use.
- Use the options on the Subdivision page to specify the resolution in U
and V.
- Use the options on the Shape page to adjust the overall shape of the
blend. For information about each parameter, click the help icon.
Blending surfaces
Input surfaces
88 • SOFTIMAGE|XSI
Resulting blend
Creating Surfaces
Filleting Intersections
A fillet is a surface that smooths the intersection of two others, like a molding
between a wall and a ceiling.
To create a fillet
1. Select one of the intersecting surfaces in Object mode.
2. Choose Create > Surface > Fillet Intersection from the Model toolbar. If
you change your mind, press the Esc key to cancel the operation.
3. Pick the other surface. A fillet is created and the Fillet Intersecting Surfaces
property editor opens.
4. Adjust the options as desired:
- Specify the number of Subdivisions in U and V.
- Specify the Radius and Radius Type of the fillet. The fillet can have a
Constant radius, or one that interpolates from a Start to an End value in
a Linear or Cubic way. If you set the radius value too high, it may be
impossible to fit the fillet on the input surfaces.
Filleting
surfaces
Input surfaces
Resulting fillet
Shaded view
Modeling & Deformations • 89
Chapter 4 • Surfaces
Merging Surfaces
Merging two surfaces creates a third surface that spans the originals. You have the
option of specifying an intermediary curve for the merged surface to pass through.
For best results, first reparameterize the surfaces uniformly as described on page 93.
To merge two surfaces
1. Select one of the surfaces in Object mode.
2. Choose Create > Surface > Merge from the Model toolbar. If you change
your mind, press the Esc key to cancel the operation.
3. Pick the other surface.
4. Do one of the following:
- To specify an intermediary curve for the merged surface to pass through,
pick a curve.
or
- To create a merged surface without an intermediary curve, right-click in
a 3D view.
A merged surface is created and the Merge Surfaces property editor opens.
5. Set options as desired:
- If the merged surface was not created along the boundaries you wanted,
use the options on the Boundaries page to specify which boundaries of
the original surfaces to use.
- Use the Tolerance option on the Clean page to specify the maximum error
for calculating the merged surface. Lower values result in more subdivisions.
- Use the options on the Shape page to adjust the overall shape of the blend.
In particular, if you selected a curve to pass through in step 4, set Seam to
Curve. For information about each parameter, click ? for Online Help.
Merging surfaces
Input surfaces
90 • SOFTIMAGE|XSI
Single merged surface
Modifying Surfaces
Modifying Surfaces
You can modify surfaces in a variety of ways using the commands in the
Modify > Surface menu of the Model toolbar. The Insert Knot and Remove
Knot commands are described in Working with Knots and Knot Curves on
page 100.
All of the commands in the Modify > Surface menu change the
surface’s underlying topology. Topological changes are always
evaluated before any deformations, even if you applied the
deformations first. If you don’t get the results you want, try freezing
the surface’s operator stack as described in Freezing the
Operator Stack on page 30.
If you add points or knots to an object with clusters, the clusters
will shift.
Inverting Surfaces
If the normals of a surface are pointing the wrong way, you can invert it:
1. Select one or more surfaces in Object mode.
2. Choose Modify > Surface > Inverse from the Model toolbar. In the
Inverse Surface property editor that opens, leave the Inverse Surface
option checked.
When you invert a surface in SOFTIMAGE|XSI, the U direction
becomes V and V becomes U. This is different from
SOFTIMAGE|3D, where U becomes –U and V is unchanged.
Reinverting Surfaces
If you later decide that you no longer want the surface inverted, you can do
one of three things:
• Select the surface and choose Modify > Surface > Inverse again. This adds
another Inverse Surface node to the operator stack and may cause
unnecessary calculations.
or
• Select the surface and choose Edit > Modeling Properties, then uncheck
the Inverse Surface parameter on the Inverse Surface tab.
or
• Use an explorer view to expand the surface’s node and delete the Inverse
Surface operator.
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Chapter 4 • Surfaces
Opening and Closing
Surfaces
You can open a closed surface and close an open surface. A surface can be
open in both U and V like a grid, closed in both like a torus, or open in one
and closed in the other like a tube.
1. Select one or more surfaces in Object mode.
2. Choose Modify > Surface > Open/Close from the Model toolbar. The
Open/Close Surface property editor opens.
3. Specify the directions in which to open or close the surface. Closed
surfaces always open at their boundary.
Reopening and Reclosing Surfaces
If you later decide that you no longer want the surface to be open (or closed),
you can do one of three things:
• Select the surface and choose Modify > Surface > Open/Close again and
set different options. This adds another Open/Close Surface node to the
operator stack and may cause unnecessary calculations.
or
• Choose Edit > Modeling Properties, then click the Open/Close Surface
tab and change options.
or
• Use an explorer view to expand the curve’s node and delete the
Open/Close Surface operator.
Shifting UV
on Surfaces
If a surface is closed in a direction, you can shift the boundary (U = 0 or V = 0
position) along the surface.
1. Select one or more surfaces in Object mode.
2. Choose Modify > Surface > Shift UV. The Surface Shift property editor opens.
3. Adjust the Shift U and Shift V parameters. As you change values, the
corresponding boundary jumps to the nearest knot curve.
92 • SOFTIMAGE|XSI
Modifying Surfaces
Swapping UV
on Surfaces
You can swap the U and V directions on a surface. This simply changes which
direction is considered U and which is V for the purpose of other modeling
operations; it does not change the object’s shape. The new U direction is the
old -V and the new V is the old U, preserving the direction of the normals.
1. Select one or more surfaces in Object mode.
2. Choose Modify > Surface > Swap UV from the Model toolbar. In the
Surface UV Swap property editor that opens, leave the Swap UVs option
checked.
Reswapping U and V
If you later decide that you no longer want U and V to be swapped, you can do
one of three things:
• Choose Edit > Modeling Properties, then click the Surface UV Swap tab
and turn Swap UVs off.
or
• Use an explorer view to expand the surface’s node and delete the Surface
UV Swap operator.
or
• Select the surface and choose Modify > Surface > Swap UV again. This
adds another Surface UV Swap node to the operator stack and will cause
unnecessary calculations.
Cleaning Surfaces
Cleaning a surface reduces the number of control points while keeping the
same general shape.
1. Select one or more surfaces using the Object filter.
2. Choose Modify > Surface > Clean from the Model toolbar. The Clean
Surface property editor opens.
3. Specify the directions in which to clean. You can also set Tolerance
separately for U and V; the tolerance controls the maximum difference
between the original curve and the resampled shape.
Reparameterizing
Surfaces
Parameterization refers to the way that any position on a surface is described
in terms of the parameters U and V. Different parameterizations give different
behaviors as you manipulate the surface.
Reparameterizing surfaces does not affect how textures are applied.
In SOFTIMAGE|XSI, surfaces can have separate texture spaces.
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Chapter 4 • Surfaces
The various parameterization methods can affect the surface’s behavior when
you perform certain operations. There are four parameterization methods
available:
• With uniform parameterization, the difference between successive knots is
equal to 1 regardless of the actual length of the knot curve segment.
(While it may seem strange that non-uniform rational B-splines can have
a uniform parameterization, it is not a contradiction; “non-uniform” here
means “not necessarily uniform.”) Uniform parameterization is especially
suitable when merging.
• With non-uniform parameterization (the default), the parameterization is
not recomputed when you edit the surface. Instead, the exact shape of
your surface is preserved. For this reason, you can manipulate surfaces
with non-uniform parameterization more accurately.
• With chord length parameterization, the difference between successive
knot values is related to the actual length of each knot curve segment. If
you could see the knot values on the curve, these values might be unequal:
1, 3.2, 5.3, and so on. Chord length always strives to preserve the relation
between the length of the curve segment and the spacing of the knot
vector. When you modify the curve, the parameterization of the curve is
completely recomputed to preserve the relation of length of segment/knot
spacing. As a result of this recomputation, when you move a control
point, the surface changes slightly when you release the mouse button.
• With centripetal parameterization, the knot spacing is related to the
square root of the length of each knot curve segment. In some cases, this
may make smoother surfaces. As with chord length parameterization, the
parameterization is completely recomputed when you move points, with
the result that the surface may change when you release the mouse button.
To reparameterize surfaces
1. Select one or more surfaces in Object mode.
2. Choose Modify > Surface > Reparameterize from the Model toolbar.
3. Select a parameterization method. For a description of the available
options, see Reparameterizing Curves on page 67.
94 • SOFTIMAGE|XSI
Modifying Surfaces
To reparameterize surfaces again
If you later decide to change the parameterization again, there are three ways:
• Select the surface and choose Edit > Modeling Properties, then click on
the Reparameterize Surface tab and choose different options. The results
of later operators in the stack may be affected.
or
• Select the surface and choose Modify > Surface > Reparameterize again.
This adds another Reparameterize Surface node to the operator stack and
may cause unnecessary calculations.
or
• Use an explorer view to expand the surface’s node and delete the
Reparameterize Surface operator. This returns to the original
parameterization—later operators in the stack may be affected.
UV Parameterization and Textures
If you reparameterize a surface first then apply a UV texture support, and later
go back and change the parameterization in the original operator, the texture
may slide on the surface. This is the same behavior as in SOFTIMAGE|3D.
However, if you apply the UV texture support first and then reparameterize a
surface, the texture will not slide. This is because the texture support comes
before the reparameterization in the operator stack.
Extending Surfaces
You can extend a surface to a curve.
1. Select the surface.
2. Choose Modify > Surface > Extend to Curve on the Model toolbar. If you
change your mind, press the Esc key to cancel the operation.
3. Pick the curve. The surface is extended and the Extend to Curve property
editor opens.
4. If the wrong boundary of the surface was extended, specify the correct one
in the Boundary box. You can also specify the Continuity (degree) and
the Scaling factor.
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Chapter 4 • Surfaces
Stitching Surfaces
You can stitch the boundaries of two surfaces together. This is similar to
merging (described on page 90) but instead of creating a new surface, the
original input surfaces are modified. For best results, first reparameterize the
surfaces uniformly as described on page 93.
1. Select one of the surfaces in Object mode.
2. Choose Modify > Surface > Stitch from the Model toolbar. If you change
your mind, press the Esc key to cancel the operation.
3. Pick the other surface.
4. Do one of the following:
- To specify an intermediary curve to pass through, pick a curve.
- To stitch without an intermediary curve, right-click in a 3D view.
The surfaces are stitched and the Merge Surfaces property editor opens.
5. Set options as desired:
- If the stitch was not created along the boundaries you wanted, use the
options on the Boundaries page to specify which boundaries of the
original surfaces to use.
- Use the Tolerance option on the Clean page to specify the maximum error
for calculating the merged surface. Lower values result in more subdivisions.
- Use the options on the Shape page to adjust the overall shape. In
particular, if you selected a curve to pass through in step 4, set Seam to
Curve. For information about each parameter, click the help icon.
96 • SOFTIMAGE|XSI
Working with Points
Working with Points
You can modify surfaces by moving points as well as by selecting points or
point clusters then transforming them as described in Transforming
Components and Clusters on page 34. You can also apply deformations to
selected points and clusters in the same way that you apply them to objects;
see Chapter 6: Introduction to Deformations on page 119 for general
information about deformations, and other chapters for information about
specific deformations.
You cannot add or delete points directly. However, you can add and
delete them indirectly by adding and removing knot curves; see
Working with Knots and Knot Curves on page 100.
Selecting Points
You can select (or tag) points, add and remove points from the selection, and
select point clusters using the selection filters in the main command area or
shortcut keys. For more information about selecting in general, see Selecting
and Deselecting Objects in Chapter 5 of the Fundamentals guide.
To select points
Choose the Point selection filter on the Selection panel and drag across points
in a viewport.
Alternatively, quickly press and release the t key to activate point selection in
sticky mode, or press and hold the t key while dragging to select points in
supra mode.
Selected points are red.
To extend the selection
If both the SI3D Selection Model and Extended Component Selection
options are off in the Selection menu, use modifier keys to add or remove
points from the selection:
• Shift+drag to select additional points.
• Ctrl+drag to toggle-select points.
• Ctrl+Shift+drag to deselect points.
If either SI3D Selection Model or Extended Component Selection are on, use
the different mouse buttons to add or remove points from the selection:
• Left-click to select additional points.
• Middle-click to toggle-select points.
• Right-click to deselect points.
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Chapter 4 • Surfaces
To select clusters
Activate point selection using either the Point selection filter button or the t
key, then choose the Group/Cluster (+) selection filter in the Selection panel
and drag to select any point in the cluster.
Alternatively, if both the SI3D Selection Model and Extended Component
Selection options are off in the Selection menu, activate point selection and
middle-click to select any point in the cluster.
Selected clusters are displayed in white.
Moving Points
As an alternative to selecting and translating points, you can move points
individually using the Move Point tool:
1. Select an object.
2. Do one of the following:
- Choose Modify > Component > Move Point tool from the Model toolbar.
or
- Quickly press and release the m key to activate the Move Point tool in
sticky mode.
or
- Press and hold the m key move points in supra mode.
3. In a viewport, position the mouse pointer over a point on the object, then
click and drag to move it.
The Move Point tool has its own transformation mode “memory.” See
Transformation Modes on page 35.
Using Proportional
Modeling
When you move or transform points and point clusters, you can use
proportional modeling. When this option is on, neighboring points are
moved as well, with a fall-off that depends on distance. After you have moved
points, you can adjust the proportional settings.
To activate proportional modeling
On the Model toolbar, choose Modify > Component > Proportional. When
this option is on, neighboring points are affected any time you move or
transform points and point clusters.
To deactivate proportional modeling, choose Modify > Component >
Proportional to remove the check mark.
98 • SOFTIMAGE|XSI
Working with Points
To adjust proportional settings
1. Select the object.
2. Do one of the following:
- Choose Edit > Modeling Properties and click the Proportional tab.
There is one Proportional property page for each MovePoint operation
with proportional on.
or
- Choose Property on the Selection panel, expand a MovePoint node, and
click the Proportional icon.
3. Adjust the parameters. Click Online Help (?) for details.
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Chapter 4 • Surfaces
Working with Knots and Knot Curves
Knot curves are sets of connected knots along U or V—they are the “wires”
shown in wireframe views. You can select knot curves to use with modeling
operations such as lofting. You can also add and remove knot curves to change
the resolution of a surface.
When you add or delete knots, you change the topology of the
surface. Topological changes are always evaluated before any
deformations, even if you applied the deformations first. If you don’t
get the results you want, try freezing the surface’s operator stack as
described in Freezing the Operator Stack on page 30.
Selecting Knot Curves
To select knot curves
1. Select a surface object.
2. Choose the U Knot Curve or V Knot Curve selection filter in the
Selection panel.
3. Click in a 3D view to select knot curves:
If both the SI3D Selection Model and Extended Component Selection
options are off in the Selection menu in the Selection panel, use modifier
keys to add or remove points from the selection:
Selection filter list
- Shift+drag to select additional points.
- Ctrl+drag to toggle-select points.
- Ctrl+Shift+drag to deselect points.
If either SI3D Selection Model or Extended Component Selection are on,
use the different mouse buttons to add or remove points from the selection:
- Left-click to select additional points.
- Middle-click to toggle-select points.
- Right-click to deselect points.
Adding Knot Curves
You can add knot curves to increase the resolution of a surface. You can add
multiple knot curves at the same position (multiknots) to create sharp ridges.
1. Select a surface object.
2. Choose Modify > Surface > Insert Knot. The Insert Surface Knot
property editor opens.
3. Set the options:
- Choose the Insertion Domain for the new knot curve: Surface U or
Surface V.
100 • SOFTIMAGE|XSI
Working with Knots and Knot Curves
- Use the Knot Value slider to choose the location along U or V for the
new knot.
- Use the Knot Multiplicity slider to specify how many overlapping knot
curves to add at that location.
Knot multiplicity = 1
Knot multiplicity = 2
Knot multiplicity = 3
Removing Knot Curves
You can remove knot curves to decrease the resolution of surfaces. For
multiknot curves, you can choose how many knot curves to remove.
1. Select a surface object.
2. Choose Modify > Surface > Remove Knot. The Remove Surface Knot
property editor opens.
3. Set the options:
- Choose the Removal Domain, that is, the type of knot curve you want to
remove: Surface U or Surface V.
- Use the Knot Value slider to choose the knot curve to remove. As you
adjust this slider, the nearest knot curve is removed.
- For multiknots, use the Knot Multiplicity slider to specify how many
knot curves to remove from that location.
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Chapter 4 • Surfaces
102 • SOFTIMAGE|XSI
Chapter 5
Surface Meshes
Modeling & Deformations • 103
Chapter 5 • Surface Meshes
104 • SOFTIMAGE|XSI
Surface meshes are quilts of surfaces joined at their boundaries, just as
polygon meshes are quilts of polygons joined at their edges. They are a special
type of renderable geometry. Surface meshes are ideal for complex envelopes
on skeletons.
The component surfaces of a surface are called subsurfaces. The continuity at their
seams is maintained automatically no matter how the surface mesh is deformed.
Subsurfaces can also have their own local clusters, materials, and textures.
The main distinction between surface meshes and ordinary surfaces (such as a
primitive or a surface you create) is the number of subsurfaces. Ordinary
surfaces have just one subsurface—they can be thought of as extremely simple
surface meshes. You can select both simple and complex surface meshes with
the Surface_Mesh filter in the Selection filter list in the Selection panel.
Modeling & Deformations • 105
Chapter 5 • Surface Meshes
Building Surface Meshes
There are several parts to building a surface mesh:
1. Create a collection of separate surfaces. These will become the surface
mesh’s subsurfaces.
For example, you can import the component surfaces from scanning
software, or you can shrinkwrap curves onto a high-resolution polygon
mesh and use the curves to build the surfaces.
2. Optionally, apply the Snap Boundary operator to help align control points
along the surfaces’ boundaries.
106 • SOFTIMAGE|XSI
Building Surface Meshes
3. Assemble the surfaces into a single surface mesh.
4. Apply the continuity manager to ensure that the continuity is preserved at
the seams.
You can then deform and animate the surface mesh as desired. Each of
these stages is explained in more detail in the sections that follow.
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Chapter 5 • Surface Meshes
Considerations for Modeling Component Surfaces
There are several considerations when modeling the surfaces that will be
assembled into a surface mesh:
• All surfaces must be either cubic NURBS in both the U and V directions,
or linear NURBS in both U and V. SCM (surface continuity manager)
does not work with quadratic NURBS.
• Surface meshes work by locking boundary points together then managing
the continuity across the junction. Each boundary point can match one
and only one point on another surface’s boundary. You can insert and
remove knots to create the necessary boundary points. See Working with
Knots and Knot Curves on page 100.
• SCM uses the next row of points after the boundary to calculate
continuity. Make sure that there are enough rows between two junctions:
preferably two or more.
• The assemble operation uses distance to determine whether two points
across a junction should be locked together, so make sure points are
overlapping or very close together. You can apply the Snap Boundary
operator to help line up points along boundaries.
Junction Types
Surfaces can meet at an edge (I Junction), a T junction, or a star junction.
Alternatively, an edge of one or more surfaces may be collapsed to a single
point as at the poles of a sphere.
I Junctions
In an I junction, two surfaces are joined along a common border. This is the
simplest of all possible junctions.
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Considerations for Modeling Component Surfaces
T Junctions
In a T junction, three surfaces are joined. The border of one surface is joined to
the borders of the other two. In addition, the other two surfaces share a border.
Star Junctions
In a star junction, several surfaces come together at a point. You can have
three surfaces (Y junction), 4 surfaces (X junction), or more. When using star
junctions:
• Make sure that the points around the star junction are more or less equidistant.
• Make sure that there are at least four control points between two star junctions.
• Avoid placing star junctions in areas of high deformation.
Good: Points around the
junction are equidistant.
Bad: This junction will
not deform well.
Modeling & Deformations • 109
Chapter 5 • Surface Meshes
Make sure there are at least four pairs of points between star junctions.
Collapsed Junctions
In a collapsed junction, one boundary of a surface is collapsed to a point (like
at the poles of a sphere) and two opposite boundaries are joined like a cone.
Boundary collapsed to a single point.
Opposite boundaries lined up.
110 • SOFTIMAGE|XSI
Considerations for Modeling Component Surfaces
Multiknots
You can use multiknots (created by overlapping control points) to create
discontinuities that help to line up surfaces. This is especially useful to
eliminate holes where three or more surfaces meet in a complex way.
Three surfaces meeting at a point
can pose a problem.
Simply joining them at the central
point causes overlapping edges.
To solve the problem, create knots of
multiplicity 3 (shown here with an outline).
The multiknots create a discontinuity that
helps align the surfaces. Continuity is
maintained across the multiknot curves as
if they were junctions.
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Chapter 5 • Surface Meshes
Snapping Boundaries
Snapping boundaries constrains the control points on the boundary of one
surface to the matching control points on the boundary of another. This is
useful when you are aligning points on boundaries before assembling a
surface mesh.
1. Select one of the surfaces.
2. Set the selection filter to Boundary and select the boundary to which you
want to snap points.
3. Choose Create > Surf Mesh > Snap Boundary from the Model toolbar.
4. Click to pick the second surface, then click again to pick the boundary you
want. The boundary points of the second surface snap to the first, and the
Snap Boundary property editor opens.
5. Adjust the parameters as desired:
- Subsurface specifies the index of the subsurface that “owns” the
boundary if one or other of the surfaces you selected was already a
complex surface mesh.
- Boundary specifies which boundary to snap on the corresponding
surface.
- Inverse Boundary lines up points in the opposite direction.
- Offset is used when the two boundaries do not have the same number of
points. See the next section Snapping Boundaries with Different Numbers
of Points.
The Snap Boundary operator is persistent—any time you move the second
surface, the boundary points of the first one follow it.
Repeat the procedure to snap other boundaries together.
Snapping Boundaries
with Different
Numbers of Points
If two boundaries don’t have the same number of points, you can still snap
them. In addition, you can specify an offset to determine which points get
snapped together.
1. Using the Boundary selection filter, select the boundary with fewer points.
2. Choose Create > Surf Mesh > Snap Boundary from the Model toolbar.
3. Click to pick the second surface, then click again to select the boundary
with more points. The boundary points of the second surface snap to the
first, and the Snap Boundary property editor opens.
4. In the Snap Boundary property editor, adjust the Offset slider to control
which points get snapped to which.
5. Adjust the other parameters as desired.
112 • SOFTIMAGE|XSI
Assembling Surface Meshes
Assembling Surface Meshes
Once you have created surfaces and aligned their boundaries, you can
assemble them into a single surface mesh:
1. Select all the surfaces in Object mode. You can use the Shift key to select
multiple objects at once.
2. Choose Create > Surf Mesh > Assemble from the Model toolbar. The
Assemble NurbsMesh (SCM) dialog box opens.
3. Set parameters:
- Specify a positional tolerance for matching boundary points. Any
boundary points that are farther apart than this tolerance value will not
be joined, and the entire boundary will be excluded from continuity
management.
- You also have the option of keeping local materials and any clusters you
have defined on the surfaces.
4. Click OK. A surface mesh is created. The original surfaces remain, but
there is no modeling relation between them and the surface mesh.
At this point, the surface mesh is one object composed of separate subsurfaces.
If you snapped any boundaries, they maintain positional continuity.
If you also want them to have tangential continuity, that is, remain smooth as
the surface mesh deforms, then you should apply SCM as described in the
next section.
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Chapter 5 • Surface Meshes
Applying the Continuity Manager
When you apply the SCM (surface continuity manager) Fixer Op to a surface
mesh, it maintains the continuity across the assembled boundaries so that the
surface mesh appears seamless as it is deformed.
1. Select the surface mesh in Object mode.
2. Choose Create > Surf Mesh > Continuity Manager from the Model toolbar.
3. Set the options:
- Always Evaluate toggles the continuity manager on and off. You can
switch this off for faster performance while you work, then switch it
back on again before you render.
- Continuity determines the continuity across every junction managed by
the SCM Fixer Op: C0 (or positional continuity; that is, no holes but not
necessarily smooth) or C1 (or tangential continuity; that is, smooth).
• Only one SCM Fixer Op node can manage the continuity of a
surface mesh at any time.
• The SCM Fixer Op node is always evaluated last—it is always at
the top of the operator stack even if you apply other operators
after it.
• If there appear to be seams, these could be artifacts. Increase the
geometry approximation for a smoother result. For more
information about geometry approximation in general, see
Setting an Object’s Surface Approximation in Chapter 3 of the
Rendering guide.
114 • SOFTIMAGE|XSI
Working with Subsurfaces
Working with Subsurfaces
You can select subsurfaces or subsurface clusters, then transform as described
in Transforming Components and Clusters on page 34. You can also apply
deformations to selected subsurfaces and clusters in the same way that you
apply them to objects; see Chapter 6: Introduction to Deformations on
page 119 for general information about deformations, and see other chapters
for information about specific deformations. In addition, you can apply local
materials and textures to subsurfaces.
Selecting Subsurfaces
To select subsurfaces:
1. Select a surface-mesh object.
2. Choose the Subsurface selection filter in the Selection panel.
3. Click in a 3D view to select subsurfaces:
If both the SI3D Selection Model and Extended Component Selection
options are off in the Selection menu in the Selection panel, use modifier
keys to add or remove points from the selection:
- Shift+drag to select additional points.
Selection filter list
- Ctrl+drag to toggle-select points.
- Ctrl+Shift+drag to deselect points.
If either SI3D Selection Model or Extended Component Selection are on,
use the different mouse buttons to add or remove points from the selection:
- Left-click to select additional points.
- Middle-click to toggle-select points.
- Right-click to deselect points.
Applying Local
Materials and Textures
You can apply materials and textures locally to selected subsurfaces on a surfacemesh object. This allows you to put different materials and textures on different
subsurfaces. For more information, see Applying a Local Material and Applying
a Local Texture in Chapter 3 of the Shaders, Lights & Cameras guide.
Modeling & Deformations • 115
Chapter 5 • Surface Meshes
116 • SOFTIMAGE|XSI
Section II • Deformations
Chapter 6
Introduction to Deformations
Modeling & Deformations • 119
Chapter 6 • Introduction to Deformations
120 • SOFTIMAGE|XSI
Deformations are powerful modeling and animation tools. You can apply
deformations to objects such as polygon meshes, surfaces, and surface
meshes, as well as to hierarchies and clusters of components. You can also
apply deformations to lattices and particle clouds.
Deformations are applied as operators in the operator stack. At any time, you can
go back into the history and modify the deformations parameters—the changes
percolate up through the history and are reflected in the deformed object.
Once you are satisfied with an object, you can freeze the operator stack. This
discards the history and keeps only the current shape of an object, saving
memory and computation time for updates.
When you apply deformations to selected components, you can use a weight
map to modulate the amplitude of the deformation. This lets you paint
deformations onto objects.
If you import an object deformed by curve or surface in branch
mode from SOFTIMAGE|3D, it might not appear correctly in
SOFTIMAGE|XSI.
Modeling & Deformations • 121
Chapter 6 • Introduction to Deformations
Considerations for Deformations
Before you start applying and animating deformations, here are some of the
most important points to remember:
• All operations that modify the topology of an object (the Modify > Curve
and Modify > Surface commands) are evaluated before any deformations,
even if you applied the deformations first. If you don’t get the results you
want, try freezing the curve’s operator stack as described in Freezing the
Operator Stack on page 30.
• An object with a hierarchy provides more possibilities for deformation
animation than a single object. You can apply the deformation on the
parent selected in branch mode (middle-mouse button) or tree mode
(right-mouse button), in which case the deformation is transmitted to its
children as if the hierarchy were a single piece. You can also deform the
children individually: any deformation you apply explicitly to a child is
added to the deformation inherited from the parent.
122 • SOFTIMAGE|XSI
Modifying Deformations in the Operator Stack
Modifying Deformations in the Operator Stack
Once a deformation has been applied, it is kept in the operator stack. You can
go back and change its parameters—the object is updated automatically. For
example, if you bend an object and then randomize its surface, you can go
back and change the angle of the bend.
Modifying
Deformation
Parameters
To modify the parameters of a deformation after it has been applied, you must
reopen its property editor:
1. Do one of the following:
- Select the deformed object, choose Edit > Modeling Properties, then
click the tab for the deformation.
or
- Alt+right-click on the object in a 3D view, choose Edit > Modeling
Properties, then click the tab for the deformation.
or
- Select the deformed object, click the Property or the Select button on
the Selection panel, then click the icon of the deformation from the
pop-up explorer that opens.
or
- In an explorer view with Show > Properties on, expand the object’s
operator stack then click the icon of the deformation.
2. Modify parameters as desired.
1. The original hat
2. Result of a
deformation (Bend)
3. Result of a second
deformation (Twist)
4. Muting the Bend
yields a Twist.
Modeling & Deformations • 123
Chapter 6 • Introduction to Deformations
Muting Deformations
All deformations can be muted. This temporarily turns off the deformation,
preventing it from affecting the objects on which it is applied. This can be
useful to improve the speed of interaction in large scenes or to make other
selections and adjustments.
To mute or unmute a deformation
1. Open the deformation’s property editor as described in the previous
section, Modifying Deformation Parameters.
2. Toggle the Mute option.
When an operator is muted, the letter m appears on its icon in explorer views.
You can also mute envelope deformations in the same way. This
gives you faster performance because you can pose a skeleton
without updating the envelope. When the skeleton is in the desired
position, unmute the envelope.
Removing
Deformations
To remove a deformation from an object
1. Select the deformed object.
2. Click the Select button on the Selection panel. A pop-up explorer opens.
3. Select the deformation node’s name, then press the Delete key.
Freezing the
Operator Stack
124 • SOFTIMAGE|XSI
Freezing the were created as is, as a primitive. You can no longer go back and
modify its deformations, but you save on computer memory and time. For
more information see Freezing the Operator Stack on page 30.
Weight Maps
Weight Maps
Weight maps are properties of point clusters that let you modulate
deformations. Each cluster can have multiple weight maps so that you can
modulate different parameters in different ways.
You can create weight maps, paint weight values on them, connect them to
deformation parameters, and mix multiple weight maps on the same
parameter. You can also change the display color for weights as well as freeze a
weight map’s history.
Creating Weight Maps
Weight maps are a property of clusters.
1. Select the element to which you want to apply a weight map:
- If you select a cluster, the weight map will be applied to it.
- If you select an object, a cluster will be created for all the points on the
object and the weight map will be applied to the cluster.
- If you tag (select) points, a cluster will be created and the weight map
will be applied to the cluster.
Selected cluster
2. Choose Get > Property > Weight Map from the Model toolbar. A weight
map is applied and its property editor opens.
Modeling & Deformations • 125
Chapter 6 • Introduction to Deformations
To see the weight map in a viewport, select it and make sure that the
View mode is set to Constant or Shaded and that Show > Property
Maps is on. This options are automatically toggled on temporarily
when you activate the Paint tool.
3. Set the options you want for your base map on the Weight Map Generator
page. For example, if you set the Weight Map Type to Constant and the
Base Weight to 0, you start with a blank map for painting weights. You can
also choose from a selection of linear and radial gradients, and so on.
Blank weight map,
ready for painting
When you create a weight map it is automatically selected, so you can
immediately paint on it as described in Painting Weights on page 126 or apply
a deformation as described in Deforming with Weight Maps on page 127.
Selecting Weight Maps
Weight maps are stored under the clusters they belong to.
To select a weight map
1. Select the object.
2. Choose Explore > Property Maps from the Selection panel. A pop-up
explorer opens.
3. Select the desired weight map by clicking on its name.
Painting Weights
To paint weights on a map
1. Select the weight map.
2. Activate the Paint tool by choosing Create > Property > Paint Tool or by
pressing the w key.
The pointer changes to reflect the current brush width. You can change
the radius of the brush by clicking and dragging the middle mouse button.
To change other properties, press Ctrl+w or choose Create > Property >
Brush Properties.
3. Click and drag to add paint strokes. Use the right mouse button to remove
weight or paint negative weights.
126 • SOFTIMAGE|XSI
Weight Maps
When painting, you can increase performance by reducing the
geometry approximation settings. The Paint tool uses the
triangulation of the object to follow its surface. For more
information see Geometric Approximation Parameters on page 27.
A spot of paint
and it’s as good as new.
Deforming
with Weight Maps
If you apply a deformation when a cluster’s weight map is selected, the weight
map is automatically used to modulate the deformation’s amplitude.
1. With a cluster’s weight map selected, choose a deformation from the
Modify > Deform menu on the Model toolbar. Refer to the other chapters
of this guide for descriptions of the available deformations.
2. In the deformation’s property editor, adjust the parameters as desired.
After you have applied a deformation on a weight map, you can select the
weight map again and then press the w key to add more paint strokes.
If you select the object and choose Edit > Modeling Properties, you
see the parameters for the deformation only. However if you click on
the deformation’s icon in an explorer, you see the parameters for the
deformation and weight map together.
A slight Push is all that’s needed.
Modeling & Deformations • 127
Chapter 6 • Introduction to Deformations
Connecting
Deformation
Parameters to
Weight Maps
Any parameter that has a connection icon to the right of its slider can be
connected to a weight map. If you have already applied a deformation, you can
connect its parameters to weight maps later or connect them to different maps.
To connect a weight map
1. Open the deformation’s property editor.
2. Click on the connection icon of a parameter. A menu pops up.
3. Choose Connect. A pop-up explorer opens.
4. Navigate through the explorer and pick a weight map. The selected weight
map turns purple.
5. Click outside the pop-up explorer to close it.
The connection icon changes to show that a weight map is connected. When a
map is connected, you can click on this icon to open the weight map’s
property editor.
Some deformations have several parameters with a connection icon;
for example, Curve Deform has connection icons for Along Curve,
Along Normal, and Along Binormal. However, all parameters share
the same connection—if a weight map is connected to one
parameter, it is connected to all of them.
To disconnect a weight map
1. Open the deformation’s property editor.
2. Right-click on the connection icon of a connected parameter. A menu
pops up.
3. Choose Disconnect.
Mixing Weight Maps
You can mix multiple weight maps additively on the same parameter.
1. Open the deformation’s property editor.
2. Disconnect any weight maps that are currently connected.
3. Click on the connection icon of a parameter. A menu pops up.
4. Choose Add. A pop-up explorer opens.
5. Navigate through the explorer and Ctrl+click to toggle-select multiple
weight maps. The selected weight maps turn purple.
6. Click outside the pop-up explorer to close it. A new MappingNode weight
map is created to hold the result of the blended maps.
128 • SOFTIMAGE|XSI
Weight Maps
7. Use the parameters on the Weight Maps Mixer Op page to control the
blend. There are three parameters for each weight map in the blend:
- Use the Multiplier and Offset parameters to map weight values from
[0, 1] to the desired range using the formula
(Multiplier * Weight) + Offset. For example, to obtain a range of [-1, 1],
use a Multiplier of 2 and an Offset of –1.
- Use the Weight parameter to set the mix weight of the corresponding
weight map relative to the others in the blend.
Setting Weight-Map
Properties
You can modify weight-map properties. For example, you can change the
name or display color—this is useful if you have several weight maps on the
same cluster.
To display a Weight Map property editor
1. Select the object.
2. Choose Explore > Property Maps from the Selection panel. A pop-up
explorer opens.
3. Click on the icon of the weight map.
4. Set the options to change the weight map name or display color.
Freezing Weight Maps
Weight maps can be frozen. This collapses the weight map generator (the base
constant or gradient map you chose when you created the weight map)
together with any strokes you have applied. After you have frozen a weight
map, you can still add new strokes but you cannot change the base map or
delete any strokes you performed before freezing.
1. Select the weight map.
2. Click the Freeze button on the Edit panel in the Edit panel.
Modeling & Deformations • 129
Chapter 6 • Introduction to Deformations
130 • SOFTIMAGE|XSI
Chapter 7
Basic Deformations
Modeling & Deformations • 131
Chapter 7 • Basic Deformations
132 • SOFTIMAGE|XSI
There are a variety of basic deformations you can quickly apply to objects. The
parameters of each deformation are set in a single property editor and require
no other input, so you can modulate the deformation easily. The
deformations can be applied to objects, hierarchies, and clusters. With
clusters, you can use weight maps to further modulate the deformation.
Modeling & Deformations • 133
Chapter 7 • Basic Deformations
Applying Basic Deformations
You can apply a basic deformation to an object, hierarchy, or cluster. With
clusters, you can also modulate the deformation with a weight map.
1. Select the object, hierarchy, cluster, or weight map.
Undeformed hat
2. Choose one of the basic deformations from the Deform menu on the
Model or Animate toolbar:
- Bend folds an object. You can specify the axis that gets bent, the angle of
the bend, the radius over which the bend occurs, the position where the
bend starts, and the direction of the bend.
Bend deformation
- Bulge pushes an object’s points out from the center. You can specify
which axes the deformation occurs on, as well as the reference axis, the
amplitude, and the amplitude’s profile.
Bulge deformation
134 • SOFTIMAGE|XSI
Applying Basic Deformations
- Shear pulls the ends of an object in opposite directions. Again, you can
specify which axes the deformation occurs on, as well as the reference
axis, the amplitude, and the amplitude’s profile.
Shear deformation
- Taper gradually scales an object in one direction. Yet again, you can
specify which axes the deformation occurs on, as well as the reference
axis, the amplitude, and the amplitude’s profile.
Taper deformation
- Twist progressively rotates an object in one direction. You can specify
the axis or rotation, the maximum angle, and the angle’s modulating
profile. You can also use this deformation to create a vortex, where the
amplitude of the rotation depends on the distance from the axis.
Twist deformation
Modeling & Deformations • 135
Chapter 7 • Basic Deformations
- Push moves points in the direction of their normals. You can specify the
amplitude.
Push deformation
- Randomize moves points around randomly. You can specify the
maximal displacement in each axis, the number of repetitions, and the
way that random values are generated.
Randomize deformation
- Shape Jitter is like an animated Randomize. You can additionally specify
time control options.
Shape jitter deformation
3. Adjust and animate the parameters as desired. Click Online Help (?) for
information about every parameter on a page.
136 • SOFTIMAGE|XSI
Chapter 8
Deforming by Cluster
Modeling & Deformations • 137
Chapter 8 • Deforming by Cluster
138 • SOFTIMAGE|XSI
A cluster is a named group of components that are grouped together for a
specific modeling or animation purpose. By grouping and naming
components, it makes it easier to work with that same group of components
again and again. For example, by grouping all points that form an eyebrow,
you can easily deform the eyebrow as an object instead of trying to reselect the
same points each time you work with it.
A cluster stores only an index plus a vector for each component, not all
geometry information of each point in the cluster. You can define as many
clusters on an object as you like, and the same component can belong to a
number of different clusters.
You can define clusters for points, edges, polygons, and subsurfaces. Each
cluster can contain one type of component. For example, a cluster can contain
points or polygons, but not both.
Spinning top
with two clusters
Top
Bottom
Modeling & Deformations • 139
Chapter 8 • Deforming by Cluster
Cluster Basics
You can create and select clusters, set viewing options, and add and remove
components.
If you add points or knots to an object with clusters, the clusters will
shift.
Creating a Cluster
To create a cluster of components on an object
1. Select an object.
2. Select some components using one of the following methods:
- On the Selection panel, specify the type of component, then use the
mouse to select.
- Press the t key for points or the y key for polygons, then left-click to
select, middle-click to deselect, and right-click to toggle the selection
status of components.
3. Choose Edit > Create Cluster from the Edit panel. A cluster is created and
automatically selected.
4. If desired, press Enter to open the cluster’s property editor and change the
default name. You can also change the default display color for unselected
clusters—this is useful if you have many clusters on the same object.
Clusters are also created automatically if you apply a deformation or
store a shape key on selected components.
Selecting Clusters
You can select clusters using the buttons on the Selection panel, by clicking in
a 3D view or by using the explorer. Selected clusters are displayed in white.
To select a cluster using the Selection panel
1. Select the object that contains the cluster.
2. Click the Cluster button on the Selection panel. A transient Explorer
opens, listing the available clusters on the object.
3. Click on a cluster’s name to select it.
140 • SOFTIMAGE|XSI
Cluster Basics
To select a cluster in a 3D view
1. Select an object with a cluster.
2. Do either of the following:
- Activate the filter for the desired type of component on the Selection
panel; alternatively, press the t key for points or the y key for polygons.
Next, choose the Group/Cluster (+) selection filter then click and drag
to select any component in the cluster.
or
- If both the SI3D Selection Model and Extended Component Selection
options are off in the Selection menu, switch point selection on and use
the middle mouse-button to select any point in the cluster.
3. The entire cluster is selected. If the selected components belong to
multiple clusters, all clusters that contain them are selected. You can use
the Select button on the Selection panel to refine the selection list.
To select a cluster in an explorer
1. Make sure that Show > Clusters is on.
2. Expand the object’s node, then its operator stack (first child node), then
its Clusters folder.
3. Click on the cluster’s name.
Viewing Clusters
You can toggle on or off the display of clusters in the 3D views, change cluster
display colors, and display cluster reference frames.
Displaying Clusters
You can change how clusters are displayed in each of the 3D views by doing
one of the following:
• To quickly toggle the display of clusters on selected objects, choose
Clusters from an individual viewport’s Show menu or from the View
menu on the main-menu bar to set all viewports.
or
• For more options, display the Visibility Settings property editor by
choosing Visibility Options from an individual viewport’s Show menu or
from the View menu on the main-menu bar to set all viewports. Modify
the settings on the Clusters property page.
Modeling & Deformations • 141
Chapter 8 • Deforming by Cluster
Changing Cluster Display Colors
You can also change the display color of each cluster individually. This makes
it easy to distinguish clusters on a complex model.
1. Select a cluster and press the Enter key. The Cluster property editor opens.
2. Use the sliders to adjust the red, green, and blue components of the
cluster’s display color.
Cluster Reference Frames
When working with clusters, you may find it useful to display the cluster
reference frames. The reference frame acts like a center for the selected clusters
or components. It defines the reference axes when you transform clusters in
Local mode. To display cluster reference frames:
1. In a viewport, choose Show > Visibility Options to edit the properties of
that viewport. Alternatively, choose View > Visibility Options (All Views)
from the main-menu bar to edit the properties of all viewports.
2. On the Attributes tab of the Visibility Settings property editor, set the following:
- Cluster Reference Frame displays an axes indicator for the selected
clusters or components.
- Cluster Reference Frame Info displays the XYZ position of the
reference frame.
Cluster reference frame
Adding Components
to Clusters
To add components to an existing cluster
1. Select an object with a cluster.
2. On the Selection panel, specify the type of component. Alternatively, press
the t key for points or the y key for polygons.
3. Select a cluster with the middle mouse button.
4. Holding the Shift key down, select components with the left mouse button.
5. Choose Edit > Add to Cluster from the Edit panel.
142 • SOFTIMAGE|XSI
Cluster Basics
Removing
Components
from Clusters
To remove components from a cluster
1. Select an object with a cluster.
2. Select a cluster.
3. Holding the Shift key down, select components with the left mouse button.
4. Click the Uncluster button or choose Edit > Remove from Cluster from
the Edit panel.
Clusters’ Last Stand
To remove a cluster
Removing a cluster removes the group but does not remove the components
from the object. To remove a cluster from an object.
1. Select an object with a cluster.
2. Select a cluster.
3. Click the Uncluster button or choose Edit > Remove Cluster from the
Edit panel.
Alternatively, you can delete a cluster using the explorer view.
Animating Clusters
You cannot animate cluster transformations directly. Instead, you can use the
Cluster Center deformation as described in Deforming by Cluster Centers on
page 144 or use shape animation as described in Chapter 12: Shape Animation
of the Animating guide.
Modeling & Deformations • 143
Chapter 8 • Deforming by Cluster
Deforming by Cluster Centers
You can assign the center of a cluster to a deformer like a null or other object.
The cluster is constrained to the center and you can deform the object by
moving the center. You can animate the deformation by animating the center.
This is especially effective if you use a weight map to create a falloff that
modulates the amplitude of the deformation.
You can create a null and assign it as the center when you create a cluster, or
you can create a cluster and assign a center later.
Transform the null...
...to transform
the cluster.
In SOFTIMAGE|XSI, cluster centers are implemented as a
deformation operator. You can mute the deformation, use weight
maps, and so on, like any other deformation.
To create a cluster and a center
1. Select components on an object.
2. Choose Edit > Create Cluster with Center from the Edit panel. A cluster
and a null are created, with a Cluster Center deformation already applied.
The null center is automatically selected.
3. Modify and animate the scaling, rotation, and translation of the null to
affect the cluster.
144 • SOFTIMAGE|XSI
Deforming by Cluster Centers
To assign a center to a cluster
1. Create an object to act as the cluster center. You can use any type of object;
you are not restricted to nulls.
2. If desired, create a weight map for the cluster as described in Creating
Weight Maps on page 125.
3. Make sure that the cluster (or the weight map, if you are using one) is
selected, and choose Deform > Cluster Center from the Model or
Animate toolbar.
4. Pick the null. The Cluster Center property editor opens.
5. Lock the Cluster Center property editor to prevent it from updating, then
select and move the null. Adjust the parameters on the Cluster Center
property editor to achieve the desired effect; for details open Online Help
(?).
To achieve the same effect as SOFTIMAGE|3D when rotating, make
sure that SI3D Rotation is on—rotations are performed around the
center’s center. When this option is off, rotations are performed
around the cluster’s reference frame.
Modeling & Deformations • 145
Chapter 8 • Deforming by Cluster
146 • SOFTIMAGE|XSI
Chapter 9
Spatial Deformations
Modeling & Deformations • 147
Chapter 9 • Spatial Deformations
148 • SOFTIMAGE|XSI
Spatial deformations are like space warps: they work by distorting the regular,
orthogonal space in which an object exists and moves. For example, you can
deform an object by a curve so that its Y axis follows the shape of the curve, or
you can deform by a surface so that the object’s XY plane follows the surface’s
UV. The object appears to be distorted, but it is actually preserving its shape
relative to its own distorted space.
Modeling & Deformations • 149
Chapter 9 • Spatial Deformations
Deforming by Curves
Deformation by curve distorts an object by remapping the Y axis to any curve
you pick. You can animate the object in the deformed space defined by the
curve, and you can also animate the shape of the curve itself.
Since deformation by curve uses the Y axis, you need to build the object so that
the axis you want facing forward along the curve is pointing up in the positive Y
direction. If you can’t build your model this way, translate and rotate the model
until it is at the origin and faces up in positive Y. Choose Transform > Reset
Center - All Transforms to freeze the object before continuing, or use the
options on the Constraint page when you apply the deformation.
Object and curve before the deformation is applied
150 • SOFTIMAGE|XSI
Object and curve after the deformation is applied
Deforming by Curves
To deform by curve
1. Create a curve using any of the available tools. Note that if the curve
contains extremely sharp bends, the object may become severely distorted.
For information about curves in general, see Chapter 3: Curves on page 51.
2. Select the object, branch, group, or model you want to deform.
3. Choose Modify > Deform > by Curve from the Model toolbar.
4. Pick the curve. The center of the deformed object snaps to the beginning
of the curve, and the Curve Deform property editor opens.
5. Use the Translation, Scaling, and Roll parameters to move the object in
deformed space. You can still use the standard SRT commands to move
the object in ordinary space.
6. If you moved either the curve or the object from the global scene center
before applying the curve deformation, you can compensate with the
options on the Constraint page:
- If you moved the object before deforming, turn Constrain to Deformer on.
- If you moved the curve before deforming, turn Constrain to Deformee on.
- If you moved both, turn both options on.
If you deformed an object by a curve, you should freeze its operator
stack before using it as an envelope.
If you import an object deformed by curve in branch mode from
SOFTIMAGE|3D, it might not appear correctly in
SOFTIMAGE|XSI. This is because of basic differences in how
deformation by curve is implemented. However, it should still be
possible to recreate the original effect by modifying the Curve
Deform parameters in SOFTIMAGE|XSI.
Modeling & Deformations • 151
Chapter 9 • Spatial Deformations
Deforming by Surfaces
Deformation by surface distorts an object by remapping the XZ plane to the
UV space of a surface you pick. You can animate the object in the deformed
space defined by the surface, and you can also animate the deforming surface.
Object and surface before the
deformation is applied
Object deformed by the surface
To deform by surface
1.
2.
3.
4.
Create a surface of any shape using any of the surface or deformation tools.
Select the object, branch, group, or model you want to deform.
Choose Modify > Deform > by Surface from the Model toolbar.
Pick the surface. The object deforms and the Surface Deform property
editor opens.
5. Use the Translation, Scaling, and Roll parameters to move the object in
deformed space. In particular, if the object is severely distorted, try using
the Scale parameters to shrink it.
You can still use the standard SRT commands to move the object in
ordinary space.
6. If you moved either the surface or the object from the global scene center
before applying the curve deformation, you can compensate with the
options on the Constraint page:
- If you moved the object before deforming, turn Constrain to Deformer on.
- If you moved the surface before deforming, turn Constrain to Deformee on.
- If you moved both, turn both options on.
If you deformed an object by a surface, you should freeze its
operator stack before using it as an envelope.
If you import an object deformed by surface in branch mode from
SOFTIMAGE|3D, it might not appear correctly in SOFTIMAGE|XSI.
152 • SOFTIMAGE|XSI
Deforming by Lattices
Deforming by Lattices
Lattices make it easy to deform a large amount of geometry at once. They
allow you to deform objects by warping the 3D space around them. A lattice is
a control box with a variable resolution, looking rather like scaffolding
surrounding an object. When you move a point on a lattice, its original
location in space is mapped to its new location. This warps the space between
points, and objects that are affected by the lattice become distorted.
Lattice deformations have two parts:
• A lattice object.
• A Lattice deformation operator on each object deformed by the lattice.
You can set the properties for these parts independently, so that several objects
can be deformed in different ways by the same lattice object.
Unlike in SOFTIMAGE|3D, lattices are not a special type of
geometry. You can select and transform points, move points, create
clusters, assign cluster centers, apply deformations, use shape
animation, and so on, just as with other 3D objects.
Lattices do not need to be the parent of the deformed objects. However,
to obtain similar results to SOFTIMAGE|3D when transforming
lattices, make the deformed objects the children of the lattice.
Scenes with lattice animation might not be imported correctly. There
may be differences because transitions in SOFTIMAGE|XSI
transitions are between two shape clips, while in SOFTIMAGE|3D
transitions are between all shape keys. You can fix this problem in the
animation mixer by mixing weight curves instead of using transitions.
Deform objects by
moving points on
lattices.
Modeling & Deformations • 153
Chapter 9 • Spatial Deformations
Creating and Applying
Lattices
You can create a lattice and apply it to an object at the same time:
1. Select the object, branch, group, or model you want to deform.
2. Choose Get > Primitive > Lattice from the Model toolbar. A lattice is
created to fit the object, and the lattice’s property editor opens.
3. You can set the lattice’s subdivisions in each axis; more subdivisions give
greater resolution for the deformation.
You can also set the interpolation type along each axis. Curve yields
smoother deformations than Linear.
Undeformed
Linear
interpolation
Curve
interpolation
4. Deform the lattice in any way. For example, you can select and move
points, use clusters, or apply any other deformation to it. You can also
animate the lattice’s deformation.
As the lattice deforms, the object deforms with it.
Applying an
Existing Lattice
You can also apply an existing lattice to objects:
1. If necessary, create a new lattice by first deselecting all objects then
choosing Get > Primitive > Lattice from the Model toolbar. A lattice is
created and the Lattice property editor opens. You can set the lattice’s
subdivisions and interpolation type.
2. Select the object, branch, or model you want to deform.
3. Choose Modify > Deform > by Lattice.
4. Pick the lattice. The Lattice deformation property editor opens.
5. Deform the lattice in any way.
154 • SOFTIMAGE|XSI
Deforming by Lattices
Setting Lattice
Deformation
Properties
You can set various properties for the Lattice deformation operator on each
object deformed by a lattice.
To open the Lattice deformation property editor
Do one of the following:
• Select the deformed object, choose Edit > Modeling Properties, then click
the Lattice tab.
or
• Alt+right-click on the object in a 3D view, choose Edit > Modeling
Properties, then click the Lattice tab.
or
• Select the deformed object, click the Property or the Select button on the
Selection panel, then click the Lattice icon from the pop-up explorer that
opens.
or
• In an explorer view with Show > Properties on, expand the object’s
operator stack then click the Lattice icon.
Setting the Scope of Lattice Deformations
By default, all points on an object are deformed by a lattice no matter where
they are in space. You can set the Deformation Scope in the Lattice
deformation property editor so that only those points that are within the
lattice object itself are affected:
• All Points deforms the entire object no matter where it is.
• Points Inside Pre-deformed Lattice deforms only those points that would
currently be within the undeformed lattice’s shape. As you move the
object away from the lattice, points that fall outside are not affected.
Position of undeformed lattice
Deformation Scope = All Points
Deformation Scope =
Points Inside Pre-deformed Lattice
Modeling & Deformations • 155
Chapter 9 • Spatial Deformations
Scaling
You can control how an object is affected when the lattice object is scaled by
setting the Scaling Mode option in the Lattice deformation property editor:
• No Scaling—The deformed object is not scaled when the lattice object is
scaled. However, the deformed object is still affected as the lattice’s points
move when scaled.
• Treat Scaling as Deformation—The deformed object is scaled before the
lattice deformation is applied.
• Apply Scaling to Geometry (SI3D)—The lattice deformation is applied first,
then the deformed object is scaled. This is the behavior in SOFTIMAGE|3D.
156 • SOFTIMAGE|XSI
Deforming by Spines
Deforming by Spines
Deformation by spine lets you change an object’s shape using curves as
deformers, similar to the way that you can deform envelopes by moving bones
in a chain. Each curve defines a cylinder of influence with an associated
radius, and object points within a curve’s influence are assigned to that curve.
If an object point is close to two or more curves, it is weighted between them.
However, unlike envelopes, you cannot manually adjust the weighting.
To deform by spine
1. Create the curves for deforming the object. The curves should be as close to
the object’s surface as possible; otherwise, points on the object’s surface may
fall outside the curve’s radius of influence. Also, note that the closer the
curves’ points are to the object’s points, the more closely the deformation of
the object’s surface will follow the curves’ points as you move them.
Surface and curve
You can use the Shrinkwrap deformation to project curves onto the
object’s surface. Don’t forget to freeze the shrinkwrapped curves
before using them with Deform by Spine. For more information
about Shrinkwrap in general, see Chapter 10: Shrinkwrap on page 163.
2. Select the object you want to deform.
3. Choose Deform > By Spine. This command is available under Modify on
the Model toolbar as well as under Deform on the Animate toolbar.
4. Pick the curves you want to act as deformers.
5. When you have finished picking curves, click the right mouse button in a
geometry view. Clusters are created and colored according to the
deformer, and the Deform by Spine property editor appears.
Modeling & Deformations • 157
Chapter 9 • Spatial Deformations
Clusters on the surface
6. Adjust the values as desired:
- Falloff Amplitude controls the modulation of the deformation along the
radius of influence from the curve to the edge of the effect.
- Radius controls the base width of the cylinder of influence in
SOFTIMAGE units.
- Longitudinal Radius controls the actual width of the cylinder of influence
as a fraction of the base Radius along the percentage length of the curve.
7. Select a curve deformer and use it to change the shape of the object. Any
change you make to a curve deformer is reflected in the shape of the
object. For example, you can:
- Translate, rotate, or scale the curve.
- Move points, either using the Move Point tool or by selecting points and
transforming them with the SRT tools. You can also add points to the
curve for finer control. For more information, see Modifying Curves on
page 65.
- Apply deformations like Twist and Bend to the curve.
Move the curve to pull the points.
158 • SOFTIMAGE|XSI
Deforming by Spines
Modifying
Spine Weights
Spine deformations use the same mechanism as envelopes for weighting
points to deformers. You can modify the weights of points in a spine
deformation either manually or by painting. Both methods use the envelope
weight editor.
Each point on an envelope has a total weight of 100%, which is divided
between the deformers to which it is assigned. For example, if a point is
weighted by 75% to deformer A and 25% to deformer B, then A pulls three
times as strongly as B on the point.
Displaying the Envelope Weight Editor
To display the envelope weight editor for a spine deformation
1. Select an object deformed by spine.
2. Choose Deform > Envelope > Edit Weights on the Animate toolbar, or
press Ctrl+e.
Choose a
weight option.
Change how the
selected point is
weighted to the
selected deformer.
Select a deformer to
modify how points
are weighted to it.
Select a point to
modify its weight.
View how the
selected point is
weighted to
different deformers.
Choose a different display color
for deferrers and points.
Points highlighted in green are
weighted to the selected deformer.
Modeling & Deformations • 159
Chapter 9 • Spatial Deformations
The first time you open the envelope weights editor, you will
probably need to resize it to see all the controls. To keep the new size
for future sessions, first close the editor and then save your layout.
For more information about saving layouts, see Customizing the
Layout in Chapter 8 of the Fundamentals guide.
If you will be working for a while with the envelopes weight editor,
it’s a good idea to lock it to prevent it being recycled by other
property editors.
Selecting Deformers
To select a deformer, click on it in the Deformers column. The selected
deformer is highlighted in white in the 3D views. Points that are wholly or partly
weighted to the selected deformer are highlighted in green in the Elems column.
Selecting Points
To select a point, click on it in the Elems column. The selected point is
highlighted in white in the 3D views. The Wghts column shows how the
selected point is weighted to all the deformers.
You can also select multiple points. Click and drag to select a range of points.
Ctrl+click to select or deselect multiple points individually.
Showing Selected Points
Because the list of points is often very long, you can restrict it to the points
you are working on. In a 3D view, tag the points using the t supra key. To show
all points again, untag all points.
Modifying Display Colors
You can change the display color for deformers and their point clusters, as
well as set the threshold for displaying points in a deformer’s color. To display
deformer colors on points in 3D views, make sure that Show > Clusters is on.
To change deformer colors
To change the display color of a deformer and its point cluster in 3D views,
click on a color swatch and use the color editor.
160 • SOFTIMAGE|XSI
Deforming by Spines
To change color thresholds
By default, points that are assigned 50% or more to a deformer are displayed in
the corresponding color. To change this threshold for a particular deformer:
1. Find the deformer in the Deformers column of the envelope weights
editor, then find the name of its cluster in the corresponding row of the
Clusters column.
2. Click the Clusters button on the Selection panel, then click the icon of the
deformer’s cluster. The cluster’s property editor opens.
3. On the Envelope Selection Clusters Op page, set the Weight Threshold to
the desired value.
Setting Weight Options
You can modify weights by painting or by editing them manually, as described
in the sections that follow. Either way, the weight options determine how the
weights are affected by values you set:
• Absolute sets the weight to exactly the value you apply.
• Additive adds or subtracts an amount to the current weight.
• Add Percentage adds or subtracts a percentage of the current weight.
Editing Weights Manually
To edit spine deformation weights manually
1. In the envelope weights editor, select a point in the Elems column.
You can select multiple points in the Elems column, but note that the
displayed weight values reflect only the first point selected.
2. Select a deformer in the Deformers column.
3. Use the Weight slider to adjust how the selected points are weighted to the
deformer according to the current Weight Options. Alternatively, you can
type values directly in the Wghts column.
Modeling & Deformations • 161
Chapter 9 • Spatial Deformations
Painting Weights
To paint spine deformation weights interactively in a viewport
1. Display the envelope weights as described in the previous section.
2. Press the w key to activate the Paint tool.
The pointer changes to reflect the current brush width. To change the
width, click and drag with the middle mouse button. You can also set the
radius and other brush properties by choosing Get > Property > Paint
Properties or pressing Ctrl+w.
3. Click on the name of a deformer in the envelope weights editor to select it
and paint in its color.
You can toggle the display of weight maps for individual deformers on
or off by clicking in the Vis. column. To make it easier to see the
weights you are painting, turn off the display for the other deformers.
4. In a viewport, click and drag to paint on the envelope. Use the left mouse
button to add weight and the right mouse button to remove weight.
When painting, you can increase performance by reducing the
geometry approximation settings. The Paint tool uses the
triangulation of the object to follow its surface. For more
information see Geometric Approximation Parameters in Chapter 1
of the Modeling & Deformations guide.
Freezing Envelope Weight Maps
You can freeze spine deformation weight maps. This operation collapses the
weight map’s operator stack, removing the individual paint stroke operations.
It also removes the ability to change the falloff and radius of the cylinder
of influence.
1. Make sure that the envelope weight map is selected. To select it, first select
the envelope then click the Property button on the Selection panel,
expand the Envelope Operator node, and click on the name of the map
Envelope_Weights.
2. Choose Edit > Freeze Operator Stack or click the Freeze button on the
Edit panel.
162 • SOFTIMAGE|XSI
Chap ter 10
Shrinkwrap
Modeling & Deformations • 163
Chapter 10 • Shrinkwrap
164 • SOFTIMAGE|XSI
The shrinkwrap deformation projects a wrapper object onto the surface of a
target object. You can completely engulf the target thereby giving the wrapper
the same overall shape, or you can apply the wrapper onto the target like a decal.
You are not restricted in the type of objects that you can shrinkwrap. You can
shrinkwrap any combination of surfaces, surface meshes, polygon meshes,
and curves onto other like objects.
Deforming surface mesh objects with multiple subsurfaces may be slow.
Sample Uses of
Shrinkwrap
Among many things, the shrinkwrap deformation can be used to:
• Create a metamorphosis between two dissimilar objects by shrinkwrapping
an object like a sphere onto each of the two objects separately, and then
selecting the resulting shapes as keys for shape animation.
• Project a curve onto a surface. For example, you can project a path onto
uneven terrain, or use a shrinkwrapped curve as a modeling aid.
• Create single-surface objects. An object like a sphere can be
shrinkwrapped to a hierarchy composed of several objects. This creates a
simpler object consisting of a single surface without seams.
• Shrinkwrap surfaces onto a high-resolution polygon-mesh object to
capture detail.
Types of Projection
When shrinkwrapping, there are several choices for how each point of the
wrapper is projected onto the target:
• Toward an inner object until they hit the surface of the target.
• Toward the center of the target.
• Along an axis.
If any points of the wrapper do not hit the surface of the target using the
selected projection type, they are not affected by the shrinkwrap deformation.
Other Shrinkwrap
Controls
With any type of projection, there are two other parameters that control the
shrinkwrap deformation: Reverse Projection and Amplitude.
Reverse Projection
The Reverse Projection option in the Shrinkwrap property editor controls the
direction in which the points of the wrapper object are projected. When on,
points are moved in the opposite direction. For example, you can project the
wrapper along an axis in the negative direction instead of the positive direction.
Modeling & Deformations • 165
Chapter 10 • Shrinkwrap
Amplitude
The Amplitude parameter in the Shrinkwrap property editor controls how far
the points of the wrapper object are moved toward the target:
• When the Amplitude is 1, the points of the wrapper object are deformed
to the surface of the target.
• Between 0 and 1, the points are deformed between their original positions
and the target.
• Below 0, the points deform away from the target.
• Above 1, the points overshoot the surface of the target.
You can use a weight map to modulate the amplitude of the shrinkwrap effect
across the surface of the wrapper object.
Effect of different
Amplitude values on a grid
shrinkwrapped to a sphere
Shrinkwrap and the
Modeling Relation
The shrinkwrap deformation maintains a modeling relation. This means that
if you transform or deform the target (or the inner object, depending on the
type of projection) after you have applied the deformation, the shape of the
wrapper is altered accordingly.
As with all deformations, you can break the modeling relation by selecting the
wrapper and choosing Edit > Freeze Operator Stack. This collapses the entire
operator stack of the wrapper.
You must always break the modeling relation by freezing the
shrinkwrapped object before deleting the target or the inner object.
Otherwise, the deformation no longer has any effect.
166 • SOFTIMAGE|XSI
Shrinkwrapping toward an Inner Object
Shrinkwrapping toward an Inner Object
To shrinkwrap toward an inner object
First, you need three objects:
• A wrapper—the object that becomes deformed. Normally it should be
outside the target object. If you want, the wrapper can completely
surround the target.
• A target—the object around which the wrapper is shrunk.
• An inner object—the object toward which the wrapper is projected until
it hits the target. It must have the same number of points as the wrapper—
each point on the wrapper is projected toward the corresponding point on
the inner object. The easiest way to create an inner object is to duplicate
the wrapper, then scale the duplicate down and move it inside the target. If
desired, you can deform the inner object so that there is more geometry
near areas where you want high detail.
Once you have created and positioned your three objects, follow these steps.
1. Select the wrapper object.
2. Choose Deform > Shrinkwrap. This command is available under Modify
on the Model toolbar, as well as under Deform on the Animate toolbar.
3. Pick the target object.
4. Pick the inner object. The Shrinkwrap property editor opens.
5. In the property editor, make sure that Toward Inner Object is selected and
set the other parameters as desired—for information about specific
parameters click Online Help (?) in the property editor.
The wrapper, target,
and inner object
Using a modified inner object
to help the shrinkwrap
Final result
Modeling & Deformations • 167
Chapter 10 • Shrinkwrap
Shrinkwrapping toward the Target’s Center
When you shrinkwrap toward the target’s center, each point of the wrapper
object is projected toward the target’s center until it hits the target’s surface. In
this case you require two objects:
• A wrapper—the object that becomes deformed. Normally it should be
outside the target object. If you want, the wrapper can completely
surround the target.
• A target—the object around which the wrapper is shrunk.
Once you have created and positioned both objects, follow these steps:
1. Select the wrapper object.
2. Choose Deform > Shrinkwrap. This command is available under Modify
on the Model toolbar, as well as under Deform on the Animate toolbar.
3. Pick the target object.
4. Right-click in a geometry view to end the picking session.
5. In the Shrinkwrap property editor that opens, make sure that Toward
Center is selected and set the other parameters as desired:
- If Bounding Box Center is off, the points of the wrapper are projected
toward the center of the target’s local coordinate system. You can move
the target’s center in Center mode, and the wrapper’s shape is altered
accordingly.
- If Bounding Box Center is on, the points of the wrapper are projected
toward the center of a bounding box containing the target. You can use
Center mode to move the center of the target’s local coordinate system
without affecting the wrapper’s deformation.
For information about other parameters, click Online Help (?) in the
property editor.
The wrapper (sphere) and target (apple)
168 • SOFTIMAGE|XSI
Result of shrinkwrapping the sphere
toward the apple’s center
Shrinkwrapping along an Axis
Shrinkwrapping along an Axis
When you shrinkwrap along an axis, each point of the wrapper object is
projected parallel to one of the axes of the target’s local coordinate system
until it hits the target’s surface. As with shrinkwrapping toward the center, you
require two objects:
• A wrapper—the object that becomes deformed. Normally it should be
outside the target object. If you want, the wrapper can completely
surround the target.
• A target—the object around which the wrapper is shrunk.
Once you have created and positioned both objects, follow these steps:
1. Select the wrapper object.
2. Choose the Deform > Shrinkwrap. This command is available under Modify
on the Model toolbar, as well as under Deform on the Animate toolbar.
3. Pick the target object.
4. Right-click in a geometry view to end the picking session.
5. In the Shrinkwrap property editor that opens, select Parallel to Axis, then
select one of the target’s local axes. Set the other parameters as desired—
for information about specific parameters click Online Help (?) in the
property editor.
Shrinkwrapping a curve along the Y axis onto a surface
Modeling & Deformations • 169
Chapter 10 • Shrinkwrap
170 • SOFTIMAGE|XSI
Chap ter 11
Waves
Modeling & Deformations • 171
Chapter 11 • Waves
172 • SOFTIMAGE|XSI
Waves are animated deformations that travel in both time and space. You can
create shock waves, water waves, and other types of natural disturbances with
wave deformations.
Wave Control Objects
and Wave Operators
There are two basic parts of a wave deformation: the wave control object and
the wave operator.
Wave Control Objects
The wave control object controls the basic parameters that are intrinsic to the
wave itself, such as its speed and shape. Each wave control object can be used
to deform any number of objects in a scene.
The wave control object is represented by a wireframe icon in the geometry
views; there are different icons for the different types of wave. The position of
the wave control object also defines the “epicenter” of the wave, and its
orientation defines the direction of the waves.
Wave Operators
The wave operator deforms an object or cluster by “attaching” a wave control
object. The wave operator is a node in the object’s operator stack. It controls
the parameters that are specific to how the wave affects a particular object,
such as the spread of the deformation. You can also use a weight map to
modulate the amplitude of the deformation across the surface.
Making Waves
Just as there are two parts to a wave deformation, there are two basic steps to
creating one:
1. Create a wave control object to define the basic wave as described in
Creating Wave Control Objects on page 174.
2. Attach the wave to objects as described in Applying Wave Deformations on
page 177.
If you are familiar with SOFTIMAGE|3D, you will find that waves
are much simpler to work with in SOFTIMAGE|XSI. For example,
you can save keyframes for a wave control object’s position just like
for any object’s position—you do not need to use a special set of
commands. In the same manner, the wave operator is treated just
like any other deformation: you can move points on the deformed
object without detaching the wave first.
Modeling & Deformations • 173
Chapter 11 • Waves
Wave Control Objects
The wave control object controls the basic parameters that are intrinsic to the
wave itself, such as its speed and shape. Each wave control object can be used
to deform any number of objects in a scene.
Creating
Wave Control Objects
To create a wave control object, choose Get > Primitive > Control Object >
Wave. The wave control object is created (as represented by a wireframe icon
in the geometry views), and its property editor opens.
You can use the wave property editor to set the wave’s basic characteristics
such as its shape and speed—these are described in the sections that follow.
However, it may be useful to first “pin” the property editor, then attach the
wave to an object as described in Applying Wave Deformations on page 177.
This way, as you change the various parameters in the editor, you can see the
effect on an object’s deformation.
You can also scale, rotate, and translate the wave control object to define its
center and the direction of the waves.
Setting
the Wave Shape
There are three parameters that control the wave shape: Type, Displacement
Direction, and Profile.
Setting the Wave Type
The Type parameter on the General tab of the wave property editor controls
how the wave moves through space. There are three options: circular, planar,
and spherical. Each type of wave is represented by a different icon in the
geometry views and is shown in the following illustrations.
• Circular—The waves move out from a point in a circular, planar pattern,
like those from a pebble dropped in still water.
174 • SOFTIMAGE|XSI
Wave Control Objects
• Planar—The waves move out from a line in a straight, planar pattern, like
boat waves hitting a beach.
• Spherical—The waves moves out from a point spherically in all
directions, like the shock waves of an explosion.
Setting the Displacement Direction
The Displacement Direction determines which way the points of deformed
objects move when they are displaced:
• Up displaces points along the local Y axis of the wave object.
• Direction displaces points in the direction in which the wave is moving.
• Normal displaces each point along the normal of the deformed object at
that point.
Modeling & Deformations • 175
Chapter 11 • Waves
Setting the Wave Profile
The shape of the wave’s displacement is controlled by the Amplitude Profile
curve on the Profiles property page of the wave property editor. You can edit
the profile using the mouse and the same keyboard commands as the
animation editor, or right-click to display a menu.
Controlling Periodicity
Waves can be periodic, meaning that the profile is repeated in space. To repeat the
wave profile, turn on Periodicity in the wave control object’s property editor.
Controlling Speed
You can control the velocity and acceleration at which the wave profile moves
through space using the Velocity and Acceleration parameters in the wave
control object’s property editor.
Controlling Falloff
You can make the strength of the wave effect fall off after a certain vertical
distance. The effect decays linearly between the Vertical Falloff Start and End
values as measured along the wave’s local Y axis.
Transforming the Wave
Control Object
Translations and rotations may be applied to wave control objects in the same
manner as ordinary objects. The wave’s effect on objects changes in the
obvious way. For example if you move a circular wave along a grid, you
change the point from which the wave emanates.
You can apply scaling as well. The icon changes shape accordingly, but the
wave’s effect on objects changes only in the following ways:
• For scaling in X and Y, the effect appears as if the profile curve were scaled
correspondingly.
• Scaling in Z does not change the effects of circular or spherical waves, but
it does change the Z-extents for planar waves. The planar-wave icon
makes this quite clear.
176 • SOFTIMAGE|XSI
Wave Operators
Wave Operators
The wave operator deforms an object or cluster by “attaching” a wave control
object. The wave operator is a node in the object’s operator stack that controls
the parameters that are specific to how the wave affects a particular object,
such as the spread of the deformation. You can also use a weight map to
modulate the amplitude of the deformation across the surface.
Before you can apply a wave deformation, you must create a wave
control object (choose Get > Primitive > Control Object > Wave) as
described on page 174.
Applying Wave
Deformations
To apply a wave deformation
1. Select the objects and clusters to be deformed. If you select a weight map,
it will be used to modulate the wave deformation’s amplitude on the
corresponding cluster.
2. Choose Deform > Wave. This command is available under Modify on the
Model toolbar, as well as under Deform on the Animate toolbar.
3. Pick a wave control object. The Wave Op property editor opens.
4. Set the parameters as desired. By default, both the Amplitude and Spread
are animated with a function curve.
Controlling Amplitude
Amplitude provides an overall scaling factor for the wave profile’s height over
time. By default it starts at 0, rises sharply to 1, and then decays slowly back to
0. This corresponds to a wave rising rapidly on a surface and then slowly
receding back to nothing.
High amplitude
Low amplitude
Modeling & Deformations • 177
Chapter 11 • Waves
Controlling Spread
Spread gives an overall inverse scaling factor to the X values of the wave
profile. For example, a value of 0.5 stretches the profile by 2 horizontally,
which has the effect of spreading the wave. By default, the spread is the
constant value 1. Certain types of waves, such as water waves, spread out as
they move. For such waves, you should edit the spread function curve to start
at 1 and end at a smaller value such as 0.5.
Wave spreads out over time
Editing Wave
Operators
The wave operator can be edited like any other deformation:
• To open its property editor, click on its icon in the object’s operator stack.
• To remove the wave deformation, select its name in the operator stack and
press the Delete key. Note that this does not affect the wave control object.
• To freeze the wave deformation as well as the rest of the operator stack,
select the object and choose Edit > Freeze Operator Stack or click the
Freeze button on the Edit panel.
Freezing removes the wave animation. The object’s shape is frozen as
deformed by the wave at the current frame when you choose Edit >
Freeze Operator Stack.
178 • SOFTIMAGE|XSI
Chap ter 12
Quickstretch
Modeling & Deformations • 179
Chapter 12 • Quickstretch
180 • SOFTIMAGE|XSI
Quickstretch is an animated deformation that changes an object’s shape
automatically, based on its motion. Quickstretch calculates deformations on
the fly, according to the object’s speed and acceleration.
There are four components of motion used to calculate quickstretch
deformation: linear velocity, linear acceleration, rotational velocity, and
rotational acceleration. These motion components are described in more
detail on page 184.
For each motion component, you can apply up to three quickstretch
deformations: flexing, stretching, and yielding. The different effects of these
deformation types is described on page 185.
Once you have applied quickstretch, you can see the effect by playing back the
animation or by simply moving the object around in a geometry view. Before
you apply quickstretch, there are several things you should check: object
centers, explicit clusters, and subdivisions.
Object Centers
Quickstretch uses the object center as the center of the deformation. For
hierarchies selected in branch mode, it uses the parent’s center. Objects with
quickstretch appear to be deformed by some force—whether active or
inertial—and the location where this force seems to be applied is the center of
the deformation.
Quickstretch uses the object center for deforming
Before You Apply Quickstretch
Before you apply quickstretch, make sure that the object’s center is located
where you want the deformation to emanate from. For example, if a building
faces such a strong wind that it bends a little, the deformation should
originate from the ground up because you would expect the building to be
attached to the ground.
If you move the center after you apply quickstretch, there is no change in the
quickstretch deformation. This is because the move-center operator comes
after the quickstretch operator in the operator stack.
Modeling & Deformations • 181
Chapter 12 • Quickstretch
Object Subdivisions
182 • SOFTIMAGE|XSI
Quickstretch looks best with many subdivisions in the deforming object, but
that can result in a great deal of computation and a heavy scene as you work.
You can use the operator stack to change an object’s subdivisions at any time,
using fewer subdivisions to help you work quickly and then adding more
subdivisions for the final result.
Applying Quickstretch
Applying Quickstretch
Before applying quickstretch, make sure you have read Before You Apply
Quickstretch on page 181.
Creating a
Quickstretch
Deformation
To create a quickstretch deformation
1. Select an object, cluster, or weight map.
2. Choose Deform > QStretch. This command is available under Modify on
the Model toolbar, as well as under Deform on the Animate toolbar. The
QStretch Op property editor appears.
3. Set the parameters as desired. On the Overview property page (default),
you can toggle the three deformation types (Flex, Stretch, and Yield) for
each motion component (Linear Velocity/Acceleration and Rotational
Velocity/Acceleration).
These toggles are also available on the other property pages, which also provide
finer control over the deformations associated with each motion component.
- Motion components are described on page 184.
- Deformation types are described on page 185.
Viewing a Quickstretch
Deformation
Once you have created a quickstretch deformation, you can view the effect in
either of the following ways:
• By playing back the animation.
or
• By using the Translate tool to move the object around in a geometry view.
Since motion vectors are computed on the fly during playback of an animated
sequence, the deformation that occurs is different if you play the animation
backward!
Similarly, if you jump from one frame to another, a huge deformation may
occur if the difference in position implies a very large velocity or acceleration.
In this case, the geometry returns to normal at the next refresh.
Modeling & Deformations • 183
Chapter 12 • Quickstretch
Motion Components
Quickstretch uses the following aspects of an object’s motion to deform the
object.
• Linear velocity
• Linear acceleration
• Rotational velocity
• Rotational acceleration
A moving object has speed or velocity. If it is changing speed, then it also has
acceleration or deceleration. For example, a car moving at a steady 100 km/h
has a velocity of 100 but an acceleration (and deceleration) of 0.
Velocity and acceleration can each be further divided into two types: linear
and rotational. For example, a car that moves along a straight line has only a
linear motion, whereas a ball that spins on the spot has only rotational
motion. Regardless of the type of motion, the faster the object is moving, the
more it is deformed.
Even if you don’t want a quickstretch deformation on an object, you
can still apply it, then mute it to calculate its velocity and
acceleration. You can then use these parameters in expressions.
184 • SOFTIMAGE|XSI
Quickstretch Deformation Types
Quickstretch Deformation Types
Whichever type of motion you give to an object, it can be deformed in one or
more ways: it can flex, stretch, yield, or do any combination of the three.
Each of these deformation types can be weighted independently of the others,
but their effects are additive.
Each effect is designed to be tweaked separately as much as possible, so that
when you use them all together the resulting deformation is more predictable.
Flexing
A flexible object when moving rapidly in one direction appears to bend or flex
in the direction of the motion, due to the resistance of the air (or water).
Stretching
In the case of a cartoon “squash and stretch” effect, the object usually elongates
in the direction of the motion and becomes thinner in the other directions.
Yielding
Depending on the mass assigned, a moving object might appear to bulge due
to the internal displacement of its mass.
Modeling & Deformations • 185
Chapter 12 • Quickstretch
Editing Quickstretch
After you have applied quickstretch, it can be edited like any other deformation:
• To open its property editor, click on its icon in the object’s operator stack.
• To remove the quickstretch deformation, select its name in the operator
stack and press the Delete key.
• To freeze the quickstretch deformation as well as the rest of the operator
stack, select the object and choose Edit > Freeze Operator Stack.
Freezing removes the deformation animation. The object’s shape is
frozen as deformed by quickstretch at the current frame when you
choose Edit > Freeze Operator Stack.
186 • SOFTIMAGE|XSI
Index
Index
Symbols
A
acceleration
quickstretch 184
animation, creating curves from 64
approximation
geometric 27
assembling surface meshes 113
Automatic Discontinuity 49
B
bend deformation 134
Bézier curves 53
birail 85
blending
curves 62
surfaces 88
boundaries
about 77
snapping 112
boundary flags
curves 55
using 77
branch mode
deformations 122
selecting 28
transformations 28
brush properties 126
B-Spline curves 53
bulge deformation 134
C
C0 continuity, curves 53
C2 continuity, curves 53
Cardinal curves 53
center deformation, cluster 144
centers 23
centripetal parameterization 67, 94
children 28
chord-length parameterization 67,
94
cleaning
curves 66
surfaces 93
closing
curves 66
surfaces 92
cluster center deformation 144
clusters
about 139
adding components 142
centers 144
constraining to objects 144
creating 140
defined 26
display colors 142
reference frames 142
removing 143
removing components 143
selecting 140
transforming 34
viewing 141
Component > Move Point 43, 70, 98
Component > Proportional 43, 70,
98
components
adding to clusters 142
creating clusters 140
defined 26
deforming 36
polygon meshes 41
removing from clusters 143
surface meshes 115
surfaces 76
constraints
cluster 144
construction history See modeling
relations, operator stack
continuity
across subsurface junctions 114
curves 53
control objects 26
waves 174
control points See points
control vertices See points
curvature continuity
curves 53
Curve > Add Point 71
Curve > Delete Point 72
curve net 86
curves
about 53
adding points 71
Bézier 53
blending 62
boundary flags 55
building surfaces 80
cleaning 66
closing 66
continuity 53
creating from animation 64
cubic 53
deforming by 150
deforming components and
clusters 36
deleting points 72
drawing 57
extracting from surfaces 60
extracting segments 60
filleting 63
fitting 61
freehand 59
intersecting surfaces 61
inverting 65
knots 55
linear 53, 59
lines 55
merging 64
multiknots 56
opening 66
points 54, 69
primitive 57
projecting onto surfaces 165
quadratic 53
reparameterizing 67
segments 55
shifting U 66
sketching 59
stitching 68
subdivisions 55
transforming components and
clusters 34
Modeling & Deformations • 187
Index
See also function curves
curves to surfaces, extending 95
CVs See points
D
deformations
about 121
bend 134
branch mode 122
bulge 134
by curve 150
by lattice 153
by motion 181
by shrinkwrap 165
by spine 157
by surface 152
cluster center 144
components 36
freezing 124
muting 124
push 136
quickstretch 181
randomize 136
removing 124
shape jitter 136
shear 135
spine 157
taper 135
tree mode 122
twist 135
vortex 135
weight maps 125
degree 0 continuity
curves 53
degree 2 continuity
curves 53
dihedral angle 49
displacement mapping
polygon meshes 50
display
properties 27
drawing curves 57
dummy objects See implicit objects
188 • SOFTIMAGE|XSI
E
edge flags See boundary flags 55, 77
edges
defined 41
deforming 36
reference frames 35
selecting 44
transforming 34
Edit > Freeze Operator Stack 30
Envelope > Edit Weights 159
Envelope Weight editor 159
Extended Component Selection
curve points 69
edges 45
polygon mesh points 42
polygons 46
subsurfaces 115
surface knots 100
surface points 97
extending
curves to surfaces 95
extracting
curve segments 60
curves from surfaces 60
extruding
curves 81
with two profiles 82
See also birail 81
F
faces 22
filleting
curves 63
surfaces 89
fitting
curves onto curves 61
flags, boundary 77
flexing (quickstretch) 185
flipping See inverting
four-sided (surfaces) 87
freehand curves 59
freezing
operator stack 30
spine deformation weight
maps 162
weight maps 129
G
GAP (generic attribute painting) See
painting
generic attribute painting (GAP) See
painting
geometric approximation
polygon meshes 48
using 27
geometry
defined 24
types of 21
global transformation mode
components 35
grids
in viewports 28
guided extrude See birail, extruding
H
hierarchies 28
history See modeling relations,
operator stack
hulls See lines
I
IGES files
exporting implicit objects 21
implicit
objects 21, 25
inverting
curves 65
surfaces 91
isolines 78
isopoints 55, 78
J
jitter, shape deformation 136
K
knot curves 77, 100
adding 100
removing 101
selecting 100
knots
curves 55
surfaces 77
Index
L
lattices
about 153
applying 154
creating 154
scaling 156
setting scope 155
linear acceleration, quickstretch 184
linear velocity (quickstretch) 184
lines, NURBS 55, 77
local materials
polygons 47
subsurfaces 115
local textures
polygons 47
subsurfaces 115
local transformation mode
components 35
lofting 83
M
maps, weight 125
merging
curves 64
surfaces 90
meshes
assembling surface 113
polygon 39
surface 105
metaballs 22
mixing
weight maps 128
Model toolbar
Refer to Online Help
modeling relation
and shrinkwrap 166
modeling relations 31
modifier stack See operator stack
Move Point tool
curves 70
polygon meshes 43
surfaces 98
multiknots
creating 100
curves 56
removing 101
surfaces 78
muting, deformations 124
N
net, curve 86
non-rendering objects See implicit
objects, control objects
non-uniform parameterization 67,
94
normals 26
nulls 22
NURBS lines, showing 55, 77
NURBS See curves, surfaces
O
object transformation mode
components 35
objects
control 26
defined 24
implicit 21, 25
opening
curves 66
surfaces 92
operator stack
about 30
modifying operators 30
operators
deleting from stack 30
P
painting
brush properties 126
deformation weights 126
spine deformation weights 162
parameterization
centripetal 67, 94
chord-length 67, 94
curves 67
non-uniform 67, 94
surfaces 93
uniform 67, 94
parenting
See also hierarchies
plotting
curves 64
points
adding to curves 71
curves 54, 69
defined 23
deforming 36
deleting from curves 72
moving 43, 70, 98
polygon meshes 41, 42
proportional modeling 43, 70, 98
reference frames 35
selecting 42, 69, 97
snapping to 28
surfaces 76, 97
transforming 34
polygon meshes 25, 39
components 41
creating 40
deforming components and
clusters 36
edges 44
faceted 49
geometric approximation 48
points 41, 42
polygons 41, 45
smoothing 49
surface approximation 50
transforming components and
clusters 34
polygons 41, 45
deforming 36
local materials 47, 115
local textures 47, 115
reference frames 35
selecting 46
transforming 34
polynodes 41
positional continuity
curves 53
Primitive > Curve 57
Primitive > Polygon Mesh 40
primitives 24
curves 57
Modeling & Deformations • 189
Index
surfaces 79
properties
display 27
Property > Brush Properties 126
Property > Paint Properties 162
Property > Paint Tool 126
Property > Weight Map 125
property maps See weight maps
proportional modeling
curve points 70
polygon mesh points 43
surface points 98
push deformation 136
Q
quadratic NURBS curves 53
quickstretch 181
deformation modes 185
R
rail See birail, extruding 81
randomize deformation 136
animated 136
reference frames
clusters 142
components 35
edges 35
relations
modeling 31
removing multiknots 101
reparameterizing
curves 67
surfaces 93
revolving 84
rotation
clusters 34
components 34
rotational acceleration
(quickstretch) 184
rotational velocity
(quickstretch) 184
S
samples 41, 55
scaling
clusters 34
190 • SOFTIMAGE|XSI
components 34
lattices 156
SCM (surface continuity
manager) 114
second-order continuity
curves 53
segments, as curve 55
selectability 27
selecting
branch mode 28
clusters 140
curve points 69
edge clusters 45
edges 44
point clusters 43, 70, 98, 141
polygon clusters 47
polygon mesh points 42
polygons 46
surface points 97
tree mode 28
weight maps 126
shape animation
and shrinkwrap 165
shape jitter deformation 136
shear deformation 135
shifting
curves 66
surfaces 92
shrinkwrap
about 165
along axis 169
projection types 165
toward center 168
toward inner object 167
SI3D Selection Model
curve points 69
edges 45
polygon-mesh points 42
polygons 46
subsurfaces 115
surface knots 100
surface points 97
sketching curves 59
snapping
boundaries 112
to points 28
to viewport grid 29
spine deformations
about 157
display colors 160
editing weights 161
freezing weight maps 162
modifying weights 159
painting weights 162
stack
operator 30
stitching
curves 68
surfaces 96
stretching (quickstretch) 185
subdivisions
curves 55
polygon meshes 40
subsurfaces 105, 115
selecting 115
Surf Mesh > Assemble 113
Surf Mesh > Continuity
Manager 114
Surf Mesh > Snap Boundary 112
Surface > Inverse 26
surface approximation
polygon meshes 50
surface continuity manager 114
surface curves
extracting 60
using 78
surface meshes
about 105
applying SCM 114
assembling 113
components 115
creating 106
selecting subsurfaces 115
snapping boundaries 112
surfaces
about 75
adding knot curves 100
birail 85
Index
blending 88
boundaries 77
cleaning 93
closing 92
components 76
creating 79
creating multiknots 100
curve net 86
deforming by 152
deforming components and
clusters 36
extending curves to 95
extending to curves 95
extruding 81
extruding (2 profiles) 82
filleting 89
four sided 87
inverting 91
isolines 78
isopoints 78
knots 77
lines 77
lofting 83
merging 90
multiknots 78
opening 92
points 76
primitives 79
removing knot curves 101
reparameterizing 93
revolving 84
selecting knot curves 100
shifting UV 92
stitching 96
surface curves 78
swapping UV 93
transforming components and
clusters 34
trim curves 78
sweep See birail, extruding 81
symmetry 29
T
W
Tag2Path 64
tagging See selecting
taper deformation 135
text 22
texture projection
freezing 30
transformation modes
components 35
transformations
branch mode 28
clusters 34
components 34
edges 34
points 34
polygons 34
tree mode 28
using 27
waves 176
translation
clusters 34
components 34
tree mode
deformations 122
selecting 28
transformations 28
trim curves 78
extracting 60
twist deformation 135
waves
about 173
amplitude 177
applying operator 177
circular 174
control objects 174
displacement direction 175
falloff 176
periodicity 176
planar 175
profiles 176
speed 176
spherical 175
spread 178
transforming 176
weight maps
applying 127
changing color 129
connecting 128
creating 125
defined 125
displaying 126
freezing 129
mixing 128
painting 126
selecting 126
spine deformation 159
U
uniform parameterization 67, 94
V
Y
yielding (quickstretch) 185
Z
zero-order continuity
curves 53
velocity
quickstretch 184
vertices See points
view transformation mode
components 35
viewing
geometric approximation 27
visibility 27
vortex
deformation 135
Modeling & Deformations • 191
Index
192 • SOFTIMAGE|XSI

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