VRay matte shadow makes noisy alpha

[hermit.crab]

Heres a scene. The cube denoises instantly in RT, but the matte shadow floor does not. If I do an offline render, it does denoise at the end, but during an RT render, I cant see any denoising to the shadow. Im using CPU rendering, and I am also using Maya...I just didnt want to start a whole new thread for it.

Thanks for the provided scene. The thing you're facing is that render elements (Alpha included) are denoised at render end, hence why the shadow catcher is not being denoised during IPR. I'm not sure if enabling it is a good idea, since it may affect performance. I need to ask around.

EDIT: Confirmed, enabling denoising of render elements would affect performance, hence why it is disabled.

[seandunderdale]

Is this not something we can have the option to turn on or off? In a shot where the only render element I have on is a denoiser (set to intel), would it impact it so much as to make the scene unusable?

[hermit.crab]

Is this not something we can have the option to turn on or off? In a shot where the only render element I have on is a denoiser (set to intel), would it impact it so much as to make the scene unusable?

I doubt it will make it unusable, but it will be slower. I guess you could add your idea to the Portal so that people can vote on it.

[hermit.crab]

seandunderdale

Did some further testing on this issue and the behaviour is the following:

1. When rendering a shadow catcher with the VFB's Background Layer and a black Environment background in Max/Maya -> we need to wait for the Alpha to get denoised at render end to affect the shadow catcher. (expected)
2. When rendering a shadow catcher with only a colored Environment background in Max/Maya -> The shadow catcher is denoised based on the RGB, although the Alpha is not.

You can use point 2 as a workaround. This way you'll get a denoised shadow catcher in IPR.