| QkQ3A.pas Updated 16 Apr 2007 | Upper levels: - QuArK Information Base - 4. The Source Code - 4.5. File-by-file descriptions

4.5.9. QkQ3A.pas | [ Prev - Up - Next ]

Code specific to Quake 3.

Index

- - Shaders (16 Apr 2007)

Shaders | Armin Rigo - 16 Apr 2007 | [ Top ]

The Quake 3 shaders are stored in a set of ".shader" files. This file format corresponds to the QShaderFile object class. Each .shader file can contain several shaders, so when loaded from disk, the QShaderFile object loads each shader in a subobject; this subobject itself is of the class QShader. Here is an example of a shader in a .shader file:
    textures/base_button/shootme2
    {
      qer_editorimage textures/base_button/shootme1.tga
      q3map_lightimage textures/base_button/shootme_glow.tga
      q3map_surfacelight 1000
      light 1
      {
        map $lightmap
        rgbGen identity
      }
      {
        map textures/base_support/metal3_3.tga
        blendFunc GL_DST_COLOR GL_ZERO
        rgbGen identity
      }
      {
        map textures/base_button/shootme_glow.tga
        rgbGen wave sin 0.5 1.0 0 .3
        blendFunc GL_ONE GL_ONE
      }
    }
A shader like this is loaded into a single QShader file with the first few lines as specific/args, that is, 'qer_editorimage' with value 'textures/base_button/shootme1.tga', then 'q3map_lightimage' with value 'textures/base_button/shootme_glow.tga', followed by 'q3map_surfacelight' with value '1000', and then 'light' with value '1'. The following brace-enclosed parts are stored in a subobject each. The name of these subobjects is what 'map' specify (just like the name of the entities in a map is what their 'classname' specify). The other specific/args are stored as is in the subobject. This was the loading process; as always in QuArK it does little more than mapping a file format into an organized hierarchy of objects with specific/args. Actual interpretation of these specific/args is given by the class of the objects : QShaderFile, which contain QShader objects, each of which contain a list of objects of class QShaderItem. QShaderFile inherits from QLvFileObject because it has no particular purpose other than being a list of shaders. QShader is more subtle. It inherits from QPixelSet because a shader can be used as a texture in the map editor. A QShader object must actually provide an image by overriding the abstract "Description" method of QPixelSet; this is needed so that the map editor knows the image it must display in places such as the 3D viewers. But a shader generally involves several texture images, in Quake 3's point of view. This means that the QShader object must build a "best-possible" single image. The easiest way to do this is to use, say, the first specified texture that is not a special one ("map $lightmap" is a special one). Be aware however that this image is just a trick required by map editing; it does not reflect the quantity of information that a whole shader actually contains. That's why QShader inherits from QPixelSet directly and not from QTexture nor QImage. The QShaderItem class, on the other hand, inherits from QTextureLnk because it is really a kind of link to a texture. It differs from QTextureLnk in its implementation of "LoadPixelSet" : a QShaderItem loads the texture based on the object name (originally the 'map' entry in the .shader file). Special names like $lightmap correspond to a default texture -- e.g. the $lightmap should be matched to a special image object similar to the 'clip' textures of Quake 1&2; in this case it would be some black image with the text 'lightmap' on it. The object structure itself is enough to make the texture browser work correctly with shaders : when viewed from inside a texture list, they display their default best-possible image, but they can also be expanded in the tree (as you would open a group) to reveal their QShaderItem sub-images. QShader itself overrides the function 'OpenWindow' so that when one clicks on a shader in the texture browser it displays a list of its QShaderItems. This is done by a form "TFQShader" overriding "TQForm2", similarly to "TFQWad", which displays the list of textures inside a QWad object. The last main issue about shaders is in an extension of QTextureLnk.LoadPixelSet, which must look for a shader when instructed to do so. In this case it loads the shader file using NeedBaseGameFile (just like a Quake 1 texture needs to be loaded from .bsp file); then it looks for the good QShader inside this QShaderFile object.

Copyright (c) 2009, GNU General Public License by The QuArK (Quake Army Knife) Community - http://quark.sourceforge.net/ | [ Prev - Top - Next ]