Does anyone understand the purpose for such functions as glVertex4f(), GL_TEXTURE_3D, etc? How can a texture be 3-dimensional? does a 4d vertex only appear at a specified point in time? How does it know what time it is? what is going on here?

a 3d texture would be something like a volumetric texture, or voxels. It''d be a nice way to display high detail models.. (think of it like transitioning from the polygon asteroids in the game asteroids to animated sprite-based asteroids in a newer game).

as for the 4d vertex.. i don''t want to try to explain.. so i''ll give this link.. the fourth coord is ''w''

http://developer.nvidia.com/view.asp?IO=understanding_w