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Actually, I'm most concerned with figure 11 in Karl's paper, which is a cumulus cloud with albedo = 1, and forward scattering g = 0.877. For some data, such as my binary checkerboard volume, delta tracking seems to outperform ratio tracking, as it skips most of the sigma_t queries when transmittance...

After more tests I still find some bias in the image. Maybe it's also necessary to also consider the compensation for passtrough rays that leave the volume. Or just use an infinite medium to compare. ps. I just worked out a compensation for passthrough rays. Seems to match multichannel and blue chan...

OK, now I get it what you meant with the code :roll: . I write it down in case someone else wonders. compensation.png And I took some time to pick up my old volumetric path tracer, improved it with the fancy stuff (hosted here, https://github.com/RNG65536/volpath ), and did some comparisons. It may ...

Residual ratio tracking is very promising, but I wonder how it's used for evaluating multiple scattering? Specifically, how to apply it to sample a free length? I only figured out how to apply it to estimate transmittance for direct illumination. As far as I remember, high variance for high albedo d...

Tonemapped using Reinhard '05 Dynamic Range Reduction Inspired by Photoreceptor Physiology

Comparing using the XYZ dragon model (up to down, dipole, dirpole and vpt): Mitsuba in (almost) the same setting:

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 ...

Have yet to read that paper. But PBRT has a good explanation on that matter. BTW, 1/pi is a like a normalization factor as in BRDF. And the diffuse Fresnel transmittance is no more than approximation to specular Fresnel transmittance from all directions. From my experience it may give darker results...

Following the shader code from http://people.compute.dtu.dk/jerf/code/dirsss/, I have compared bssrdf using dipole (Jensen'01) and dirpole (Hachisuka'15), cdipole.jpg cdirpole.jpg Both are sufficiently converged using a very small solid angle threshold(<0.25^2 sr) for hierarchical integration. The p...

You may take a look at this, http://www.cs.cornell.edu/Courses/cs6630/2012sp/notes/09volpath.pdf if you are doing path tracing. But I don't see how you can "ignore" out-scattering, since it does not contribute in the spherical integration of the radiative transfer equation, but only works for comput...