As this might have been discussed before in this forum, I haven't seen it before and didn't find anything really related when I did some searches, so here goes. For some time I've interested myself with metallic surfaces and how to create realistic looking metallic materials in MAX. There are a lot of tutorials out there on how to create metallic surfaces but most or all of them make a very narrow coverage of the subject. Most of the times they don't even discuss the theory behind, but just produce a step-by-step procedure to follow. I get the feeling that most of them don't know how a metallic surface works... which leads me to form my question: How do real world metallic surfaces work in theory? How do they respond to light that strikes them and what color are they really, behind the reflection? Do they behave in some different way than other solid materials; is it something about the particular surface structure of metallic surfaces? I do realize that there are many different kinds of metal and that there is no simple answer, but metallic surfaces can't be a complete mystery, can they? It would be very interesting to hear some of your own thoughts and methods on making your metallic materials.

Machined metal surfaces have fine grooves in the surface, due to the grains in the rotating machining tools. This can be simulated with anisotropy of varying degrees across the surface, with the anisotropy vectors in circular patterns to simulate the tool marks. The more fine the grooves, the more reflective the metal surface should be in general.

Iron, in it's pure form, is of light gray color. However, when heat treated, usually some coal and other compounds are added to achieve better surface toughness - this also tends to make the base material more dark.

Unmachined metal usually has pores in it due to material and/or mold inpurities. This can be simulated with random noise. When machined, the pores may form little "holes" in the finished surface if the porosity is severe; simulate these by cutting the bump noise output to some defined treshold.