By the way:
For an inter-reflection model to be considered physically correct, for one it
would have to be able to treat diffuse and specular reflection as one, i.e. it
should also be able to model inter-reflections of semi-diffuse surfaces. While
forward Monte Carlo tracing could _theoretically_ do this, I see no way of doing
it with a manageable number of samples.
AFAIK, POV's radiosity can do recursion because its sample rays are always
distributed around the surface normal, so it can terminate recursion for the
current ray when this ray hits an already-calculated sample. With specular
properties, the bias of the new sample rays would start to depend on the
direction of the incoming ray. So old samples could not be reused - they would
be taken from a different direction.
I'm wondering if backward tracing, like photon mapping, could overcome this
problem...
If I'm not mistaken, Radiance can do it. But Radiance uses the wavelet method,
which is completely alien to me. I don't know if (true) radiosity can model
non-diffuse reflection. For some reason, I doubt it.

Margus

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