ingenious wrote:If I remember correctly, the dirpole model includes single scattering, so in theory its result should be closer to the path traced reference. Can you actually please post that reference here for completeness?
You're right, the directional solution has included single scattering.
I had some problem with normalization, in the environment sampling PDF.
Now I think I get it working right, as I made a comparison between BRDF and light sampling,
- compare_sampling.jpg (132.55 KiB) Viewed 3835 times
I then compared between dipole, dirpole and vpt (~1k spp):
- compare_buddha.jpg (595.48 KiB) Viewed 3835 times
But the medium is not thick enough for the diffusion approximation to work efficiently, both for dipole and dirpole.
My volume path tracing routine is not unbiased. I limit the tracing depth to int(log(0.03)/log(albedo)) for each channel.
FYI, the material is skin2 from Jensen'01, and scaled by 30. The index of refraction is 1.49 for all channels.
And I used 32^2 samples for irradiance with a very naive sampler, without stratification, so that may also add to the error.
