Metropolis SDS problem?
Posted: Tue Oct 09, 2018 2:02 pm
Mainly a Cycles user I resorted to LuxRender BiDir whenever I needed better caustics.
Now with the Mac version of LuxCore it's very exciting to see the progress the developers have achieved, BiDir is now much faster and ready for HD animations on my MacBook!
Due to the yet not stable Mac version I have been experimenting with simple scenes like this: It seems that certain reflections that were rendered in Luxrender are disregarded in Luxcore: The reflections (specular) of the caustic pattern (diffuse) in the glass body that caused the pattern (specular). In my understanding these are those notorious SDS paths about which Dade said somewhere that BiDir cannot even render them by design.
Maybe it is something different but I made a comparison with the same file in LuxRender vs LuxCore and here's the result:
While caustic patterns are rendered much faster in LuxCore (clean after 1000 samples while in LuxRender still noisy after 5000) said reflections start as fireflies (see first image) and converge very slowly and get close to invisibility with further ray depth (in the top part of the second image the reflections on the backside cannot be found).
This is not a BiDir thing but presumably comes from an improved metropolis algorithm; in both renderers path vs bidir show the same result:
While the old metropolis catches those reflections immediately (see bottom part of the second image) the new one disregards them in path and bidir so that they only show in unguided sampling as fireflies.
Now with SPPM and BiDirVCM gone there is apparently no renderer available to render reflections on glass correctly except for very slow path+ sobol?
Now with the Mac version of LuxCore it's very exciting to see the progress the developers have achieved, BiDir is now much faster and ready for HD animations on my MacBook!
Due to the yet not stable Mac version I have been experimenting with simple scenes like this: It seems that certain reflections that were rendered in Luxrender are disregarded in Luxcore: The reflections (specular) of the caustic pattern (diffuse) in the glass body that caused the pattern (specular). In my understanding these are those notorious SDS paths about which Dade said somewhere that BiDir cannot even render them by design.
Maybe it is something different but I made a comparison with the same file in LuxRender vs LuxCore and here's the result:
While caustic patterns are rendered much faster in LuxCore (clean after 1000 samples while in LuxRender still noisy after 5000) said reflections start as fireflies (see first image) and converge very slowly and get close to invisibility with further ray depth (in the top part of the second image the reflections on the backside cannot be found).
This is not a BiDir thing but presumably comes from an improved metropolis algorithm; in both renderers path vs bidir show the same result:
While the old metropolis catches those reflections immediately (see bottom part of the second image) the new one disregards them in path and bidir so that they only show in unguided sampling as fireflies.
Now with SPPM and BiDirVCM gone there is apparently no renderer available to render reflections on glass correctly except for very slow path+ sobol?