Sunday, February 8, 2009

stratisfied sampling+MLT

I haven't found any papers on this subject exactly, but I had an idea (and hopefully if there is nothing out there, I can write my own paper). What I seem to have had the most trouble with in MLT was to sample uniformly(as uniformly as possible) every direction at a bounce, where applicable.  The trouble is, it is very hard to keep track of where MLT has sampled previously, and what it should do next/how it should do it next.  What I have done is essentially modified the balance heuristic in order to sample every pixel as evenly as possible
, and sample every direction as evenly as possible.  This only required slight modification to my path tracer, and does not introduce any bias.  There are numerous other subtleties, but I'd rather not go over all of them, because if It is a unique idea/implementation, I could write a paper on it, which would be nice.

With the modified balance heuristic at 51 spp at about 20 miniutes:
without the modification at 81 spp at about 30 miniutes:

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