As I heard some form of unbiased algorithm might be making its way into 
POV 3.7 at some point (similar to mcpov) I thought I'd bring up some 
thoughts/questions I had about how colours are used.

I understand that in mcpov the surface colour is determined by shooting 
out multiple rays and averaging their result, matching the real world 
closer and closer as the number of rays is increased. I also understand 
that you simulate diffuse or varying levels of blurred reflections by 
shaping the distribution of rays across the hemisphere. A very shiny 
surface (like a mirror) would only shoot rays in one direction, whereas 
a totally diffuse surface would shoot rays in all directions randomly.

My understanding from real life is that colour is handled differently in 
each case though. When I see a blue piece of plastic it's blue because 
all the light being reflected off it has its spectrum attenuated 
accordingly to make it blue. But when I see a glossy specular reflection 
(even if blurred slightly) in the same material the colour is not 
changed (white lights still appear white, not blue).

My assumption therefore is that the spectral attenuation that gives the 
appearance of colour somehow affects light more the further away the ray 
is from direct mirror reflection. It appears however mcpov does not 
allow for this. In the current POV this isn't an issue as specular and 
diffuse reflection are very clearly separated and you can choose the 
colour and amount of each, but if something like mcpov is to be 
incorporated into POV then the two terms become blurred and it's not 
clear how to correctly simulate the real life situation.

My guess is you need some kind of falloff parameter that determines how 
the diffuse colour specified affects the light as the angle increases 
away from direct mirror reflection. But that's a pure guess, I have no 
theoretical understanding of why this should be.

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