Complex numbers for diffuse map (2 maps)

[gerdich]

I would like very much to render interpolation effects of the light, like oil on a wet street. But the diffuse map gives only a material point and not a wave. Therefore interference is impossible.

With a complex number in the diffuse map you could give a wave back to the renderer. With a very little subsurface scattering interference effects should be possible.

[pixie]

This material might be what you're looking for.