>>So... the pretrace step... Is the video from that used for anything? Or
>>is the only purpose of this step to fill up the cache?
> 
> Its just to seed the cache with values (somewhat evenly distributed over the
> scene space).

OK. Whereas without that step, you would fill up one corner of the cache 
first, potentially meaning other parts don't have the influence they should?

>>...does all of this mean that the diffuse highlight options don't affect
>>radiosity?
> 
> What I said doesn't lead to that conclusion. However, those faked diffuse
> highlights (phong, specular) are indeed deliberately disabled for radiosity
> gather
> rays "since this causes problems with colors being far to bright"(quoted
> from lighting.cpp Diffuse_One_Light() ).

Right. But when I ment was, there's a keyword (roughness?) which 
controls the angle at which light affects the surface. I was trying to 
figure out whether the rad calculations take this into account.

>>Also, while we're on the subject, does radiosity take (specular)
>>reflection into account as well? (Never tried it, but I assume it does...)
> 
> Yup, real specular reflection (not the faked highlights) is taken into
> account! I've been having some fun with that lately, by disabling the
> irradiance cache and taking samples for every pixel. It's slow, but
> beautiful and funn :) The fun part is that I HAVE written software that
> lets me (and hopefully you sometime) render in parallel, so I don't go
> crazy waiting for the render :)

Mmm... sounds interesting.

Although... I suspect photon maps are faster. ;-)

Actually, I suppose you could program POV-Ray to try to illuminate an 
entire scene with photon maps. I imagine that would go real slow, 
compute a lot of photons you can't see, and generally not look so great. 
(Does photon mapping work for a depth of more than 1?)

Andrew.

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