pass for now:
- cast a shadow

wip:
- extend m3d

todo:
- create camera struct/class and walk with arrow keys, gluLookAt() ?
- enable fog
- xbox controller
- obj loader
- look at mesa's sources and borrow OSD stuff
- GL error checking and extensions
- split SDL

notes:
- texture matrix!?
- texture filtering: process of calculating color fragments from a stretched or
  shrunken texture map
 
obj loader:
- glGenTextures()
- glBindTextures()