Polygons in video games
 

Check this out:

http://halo.bungie.net/images/site/h...chiefanim2.jpg

How come all the surfaces are further subdivided into little triangles? Like the knee pad, it looks like it could just be made out of quadrilaterals, but all the quads got diagonals splitting them into two triangles anyways.

I was thinking maybe it has something to do with the whole "three points define a plane" thing but I'm not sure.

All quads get turned into tris in the end by the video card for rendering, although I don't know why the model here is triangulated at this stage.

the game engines will triangulate it, however, it may not necessarily triangulate it cleanly, so often I'd triangulate things myself to make sure the engine will display the object cleanly as I designate.