Chapter 22- Textures in the Game Engine

Chapter 22- Textures in the Game Engine
Chapter 22- Textures in the Game Engine
Since games need to be able to process operations as fast as possible, traditional
rendering techniques (specularity, ray tracing reflections and refractions) cannot
typically be processed fast enough for a game. For this reason, textures need to be
mapped differently. There are also times when you may want to use mapped textures
in an actual render. Blender does this through traditional UV Texture Mapping and a
new system called GLSL Shading. There is a lot that can be done through both of these
methods “beyond the basics” that will be discussed here. For more details, check out
the Blender wiki.
UV Texture Mapping
Think of UV Mapping like taking a box and cutting it to lay flat. The texture needs to
match each side of the box. It is difficult to do that with traditional materials and
textures. Let's say you want to model a dinosaur. The texture changes
on various parts of his body and need to be mapped correctly. This is
where UV Mapping come into play. For this example, I am going to
map the following texture I made in GIMP on a basic cube:
This is just a jpeg image that would be impossible to map as a
standard material/texture.
To begin, start with a basic scene with a cube and
change your viewport shading type from Solid to
Textured. This is the shading used during game play. You
will notice that, by default, textures are
effected by the lighting so add some lights to illuminate your scene
better and switch to the “UV Editing” window layout. This will give you
one 3D viewport and one UV Editor viewport. At
the bottom of the UV Editor viewport, hit the
Image-Open Image menu option and find the
texture you wish to use.
Now, enter Edit Mode for the cube and switch to selecting Vertices to Faces since this is
a face applying process. You can select individual faces and put UV textures on that
way, but let's “Unwrap” the cube to match our texture. This can be done for any mesh,
but we need to mark the seams where we want a split to occur. If we
look at the picture, we can see where seams should go. In order to
mark seams, we
need to switch
from Face select to Edge select.
Select the following edges (ShiftRMB) and click “Mark Seam” in the
UV Mapping section in the Tool Shelf.
These will be the unfold edges. It
should match the box layout.
Chapter 22- Textures in the Game Engine
Now go back to Face select mode, hit “A” for All twice to select all
faces. Type “U” to bring up the UV Mapping options in the 3D window.
You have several option. We want “Unwrap”. You will now see the
unwrapped faces in the UV Mapping window. You can select these
verticies as you would for any other Blender
object and move, scale or rotate them. You
will also see the texture on the cube. By
pressing “P” you will see the texture in game
play. (in object mode) Adjust the verticies so
it looks good on the cube.
By using this technique, you can select single or groups of
faces on an object to assign textures, By switching back to the
Default screen layout, you will find a panel in the Object Data
buttons, in Edit Mode, that effect the texture faces. In the
current version of Blender, you can only select one face at a
time to change these options.
Some useful options here are:
Light: face is effected by light hitting it.
Invisible: good for adding planes along a track as guides.
Collision: unchecked and the actor can go through it.
Two-Sided: by default, texture visible from one side only.
Transparency: options for visibility.
UV Textures in an Animated Movie:
Just like game physics can be written into an animation
curve, UV can be used with materials and textures. After
going through the steps above, add a material and
texture to the object. Select “Image” for the texture type,
select the picture you used, the under the
“Mapping” panel, choose “UV” in the
Coordinate box. Pressing F12 should give
you a rendered image of the map.
Chapter 22- Textures in the Game Engine
GLSL Shading
GLSL shading is very new to Blender and is an area seeing a great deal of
development. It is an attempt to add many rendering-like features to the game engine,
adding to a more realistic environment. As with the UV Mapping section, this unit will
only cover the basics to get you started.
Not all video cards are supported for GLSL shading. Some machines will be unable it
use this feature. See the Blender wiki for current specification.
To get started, we'll start a new scene and split the viewport, setting
one to UV/Image Editor.
“Blender Game” and
“Textured”. The last thing
you need to do is switch from “Multitexture” to “GLSL” shading in the
Render panel. You are now ready to work with the GLSL features in
the game engine. Not all texture and shading features are available
in GLSL, but many are and others are being developed constantly.
As mentioned before, we will only be looking at some of these
Adding Textures:
Basically, to add textures for the game in GLSL, you need to add
materials and textures the way you do for any movie. For my
example, I am working with a plane for the ground and a cube.
I've added a material and texture to the floor, using a stone
texture. The stones are too large so I need to repeat it a bit in the
texture panel. You can't use the X and Y Repeat in the “Image
Sampling” panel, but can change the size in the “Mapping”
The cube was a bit more difficult. Because the
texture wants to map as Flat by default and
GLSL does not currently work with
changing the mapping to Cube, I
had to apply the texture as we did
in the previous section using UV
Texture Mapping and mapping the texture to each face.
Remember to also switch the Mapping in the Textures
panel to UV.
Another nice feature with GLSL is
the ability to show Normal
Geometry to give a texture depth.
Looks best with a higher Specular.
Chapter 22- Textures in the Game Engine
Shadows in GLSL:
Another nice effect allowed in GLSL is the ability to cast shadows in game play. Right
now, ray tracing is not supported so your only option is to use a Spotlight with a Buffer
Shadow setting (refer to the lighting chapter for more details on setting the buffer
Currently, there is a lot of development in GLSL with new features constantly being
added. There is also a lot of work in Baking settings to improve performance. There is
work on support for indirect lighting, fluids, soft bodies and many more. For up-to-date
information, follow the Blender wiki, YouTube, and the forums.
World Settings:
While some World settings work in Multi-texture
mode and some work on GLSL Shading, Some
features do not work in either at the time (stars
for example). In Multi-texture shading, you can
get a nice effect with the Mist settings to give a
“foggy” feel to your game, but works a bit
differently in GLSL. World Horizon and Zenith
colors work differently as well.
Motion Maze Texture Exercise
Open your Motion Maze file from the last chapter. Your goal in this exercise it to make it
look good while in game play. You may use UV Texture Mapping or a combination of
UV Mapping and GLSL Shading. Find or create a nice domino texture along with
appropriate textures for all other items. Remember that for a UV Mapped texture to
work in GLSL, you need to switch to UV in the mapping panel in Textures.
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