what thing the material system should support ?
I don't know the input and output.
one implement like unity3d, it provide build in shader, and we just need to select texture. even we can make custom shader.
one implement like ogre, it seems it can real time combine shaders!
it probably depends on the engine or library in question.
for example, in dx9., materials are a way to describe how the surface of an object interacts with light, with settings like ambient, diffuse, specular, and emissive.
which particular engine or library are you interested in? the docs should have info on its particular materials system, what it does, and basically how it works.
