Denoise and shadow catcher

[Rainbow-3D]

Hello,
denoiser doesn't work on object with shadow catcher material (octane universal material), so the shadow (and/or the dark area of occlusion) keeps the noise as the denoise isn't activated.

LW 2018
Octane both version (4 and 2018)

I attach a very very simple scene. Yellow box is shadow catcher.

[juanjgon]

This seems some kind of denoiser limitation. I've asked to the core devs about it to see if it can be fixed.

Thanks,
-Juanjo

[Rainbow-3D]

Hi,
any news about denoise + shadow catcher/diffuse matte surfaces?
I'm trying to make a very white floor (need for a brochure, objects on white background, and same in videos) and the only way to get the shadow on a pure white surface is a white background + enable shadow catcher (or diffuse material with matte option, same thing I see) in the floor material, or it will be rendered gray. (maybe there is another way to get a pure white floor+shadow, but I don't find it).
So, denoise gives me a good rendering with only 300 samples. Without denoise a clear rendering needs 3000 samples.
Any idea how to resolve this?

Thank you
Gianluca

[juanjgon]

Sorry, I don't have a reply from the core devs about this issue yet, but I'll try to build a new repro scene and send it them to see what can be done.

Thanks,
-Juanjo

[Rainbow-3D]

ok, thankyou to try to resolve this problem.

Today I found another thing about shadow catcher:
Adaptive sampling stops the rendering on the shadow catcher surfaces to its MinSamples.

For example:
Max. Samples 2000
Adaptive Sampling on
Noise threshold 2%
Min Samples 15 (very low to understand better, usually 128 is good).

The rendering begins and must render 2000 samples, after 15 samples in the areas with the noise less than 2% it stop the rendering.
All works good, but on the shandow catcher surfaces it stop the rendering at 15 samples, no matter how much is the noise.
I think the engine compute the adaptive sampling on the background (in my case full white) and not on the polygons shadow catcher, like they are completely transparent.
To get a clean render on the shadow catcher surfaces too, must increase the Min Samples in adaptive sampling (usually for the shad.catch. need minimum 256), but this is a waste of time for the surfaces that are already clean at less samples.
Maybe it is always the same bug that breaks the denoise?

Thank you
Gianluca

[juanjgon]

Hi,

I've reported these issues to the core dev team to see what can be done to fix them.

Thanks,
-Juanjo

[freakanay]

Hi! Im running into exactly the same issue in C4D in the 2020.1.4 and 2020.1.5. Is there a fix for this problem by now?

[AndyM1969]

I would ask in the C4d subforum