Invisible wrote:
> Actually, that's an interesting point... Would presumably mean the very 
> first frame still takes 20 minutes, and all the subsequent ones are 
> reasonably fast unless/until you expose new geometry.

well, it might be interesting to work this out at some point ... if you were
comparing a scene lit completely with radiosity (and presuming that the
radiosity cache had already been built) against one with several traditional
point light sources, at what point does the savings of not having to trace a
shadow ray overcome the cache lookup time?

I would suspect that the answer is 'very early', except perhaps in very
simple scenes with little geometry. The more geometry is there, the more time
spent doing lookups of the bounding structure (BVH or BSP) against each
shadow ray - the more light sources, the more time, with the relationship
being fairly linear.

the rad cache lookup, however, would not suffer from this problem.

therefore it is entirely possible that, as counterintuitive as it may seem,
there is potential for a scene with global illumination to be *faster* in
interactive rendering than one without.

-- Chris

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