> (1) At the very surface of an object, specular reflection is happening,
> more or less blurred depending on how rough the surface is, and more or
> less strong depending on both the material's index of refraction and
> surface structure. This reflected light will /always/ be "white", and
> its distribution will /always/ be related to the incoming light direction.

That makes sense.

> (2) Any light that is not reflected will penetrate into the object and
> scatter around in the material, where it will be subject to filtering
> (depending on wavelength), and if it is not thus "swallowed" it will
> ultimately exit the object once again in a very random direction. This
> scattered light will /always/ be "colored" depending on the material,
> and its distribution will (almost) /always/ be (almost) totally
> independent of the incoming light direction.

Is it really a uniform colouring effect across the entire range of 
angles though? I would have thought light that scatters less will come 
out nearer to "white" and nearer the "direct" reflection angle, whereas 
the light that is scattered more will be filtered more and come out more 
randomly spread.

It's hard to judge with real materials because even with no obvious 
specular I think there are still specular effects that are extremely 
blurred, it might just be this that I'm seeing.

> MCPov does it exactly the way it should be done (except that it has a
> bug in computing the contribution from (2), getting it wrong by a factor
> of 2, but that's another story).

Is there a rule then to ensure physical correctness in mcpov when 
supplying parameters for the diffuse and reflection contributions? So 
far I've been working on diffuse+reflection=1, but it seems like that's 
wrong now.

I'm still amazed though at how easy it is to produce ultra-realistic 
lighting in mcpov with relatively little effort.

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