Some notes on optimizing OpenGL drivers for Quake3 . Only visible relief textures are candidates for updating each frame. For a candidate that we have chosen to update, we may need only update those texels which will undergo the most perceivable change, given the change in viewpoint. More than one pre-warped texture per relief texture could be cached on the card, corresponding to more than one viewpoint. Relief textures do not need to be preprocessed for viewpoints that will never be seen.
Collision detection gets harder.
This extension defines a new depth texture format. Image warping or dewarping may be implemented using texture mapping by defining a correspondence between a uniform polygonal mesh and a warped mesh. The points of the warped mesh are assigned the corresponding texture coordinates of the uniform mesh and the mesh is texture mapped with the original image. Using this technique simple transformations such as zoom, rotation, or shearing can be efficiently implemented. This is due to the relatively verbose nature of graphics APIs such as OpenGL and Direct3D. 3.