   what brdf model should i use for a "mud" or "clay" effect
  hello guys,i'm working on my sculpturing tool idea. i want to give the model a clay like appearance, or maybe a bronze like effect. but i don't know what kind of brdf model i should use.i'd like to show you some examples of the effect that i want to achieve:i especially like this effect, it looks to me like a bronze sculpture, the highlight area turns into a little bit red.i'm now picking up the cook-torrance model. but really i don't know if it is the right one to use.[Edited by - billconan on November 23, 2009 6:45:41 PM]
  i now have some screenshots to show to you.the first is the normal gl lighting, only it is a per fragment lighting in glsl:the second image is the cook-torrance lighting model, it looks like silk, not bronzemaybe i should try Oren–Nayar model instead?   ;  The effect you want is usually achived by using a blured cubemap with a simple cupmap texture lookup.if you'd like the specular highlight to move when you rotate the cam, you can calculate the reflection (or half) -vector and use it for the lookup into some seperate cubemap (or u can encode the specular intensity into the alpha channel of the diffuse-cubemap.you could checkout the FXComposer, I think it has some shaders that show that effect.btw. one nice effect you can get is by inverting the normal. It will look like some transluscent milky glass :).dont forget to check nvidia's sampleshttp://http.download.nvidia.com/developer/SDK/Individual_Samples/3dgraphics_effects.html