I'm a 3D artist trying to learn the basic (or perhaps even intermediate) level of physics of photorealistic rendering. But most artist and tutorials on the internet have little to no clue of the physics behind all the settings they tweaking to get a good rendering. I want to understand what it is I'm actually doing :)
So my question is: Why don't dielectric materials have coloured reflections like conductors? Metals like copper tint the reflection with a red-ish color, but a red rubber ball does not, why is that?
In this image you can see the reflection of the white and blue pencil is being tinted slightly yellow in the brass material.
I was once told that the white reflection was caused by the reflection of the coating material, and the coloured diffuse reflection was the reflection of the pigments inside. That makes sense for like oil based paint were you actually mix pigments in oil, and the oil becomes the white reflective coating layer, and the same thing goes for plastics I guess. The plastic is actually white or transparent but they add all the colour pigments in it.
In this image you can see the white reflections in the blue plastic, the mirror image in the plastic is NOT being tinted blue.
But what about, let's say an red apple? Is the apple peel some sort of oily coating layer filled with red pigments? Or is it just made out of "apple peel molecules" and it is simply the physical/chemical properties of these atomic/molecular bonds that effect the light in that way?