Leigh is wrong, IMHO. She seems to have learned about real-world light by examining the way CG lighting has been broken down into lighting elements. But CG lighting is really just a bunch of hacks, optimizations written for performance reasons, basically CG lighting has been written to render faster than its real-world…
in max / simple Cg world: diffuse is surface with normal at maximum 90° to the light. beyond that (backfacing light) is ambient. so in opengl or whatever you will find two color values you can tweak for light and material: diffuse/ambient. which will be picked based on normal/light relationship. however as normally those…