Black Patches in the rendered images

[basafath21]

I seem to get black patches when I try to render images in PNG / EXR file. But these black patches don't appear in Vantage view port renders.

How do I fix this issue?

[npg]

Are you rendering a sequence or a single image? The NVIDIA denoiser could produce black spots if the camera is moving through a wall or "jumping" to a new location. If you are rendering a sequence, try disabling "reduce flickering".

[basafath21]

I am trying to render a still camera.

Attached is an image showing render in progress with black patches and an image I saved from Vantage view port which does not seem to show such patches.

Please help me fix this issue.

[Alexander.Atanasov]

Could you please send a screenshot from the Vantage viewport of that portion as well?

Best regards,
Alexander

[Alexander.Atanasov]

There is something that is messing with the denoiser. Do you have the denoiser enabled in the viewport and which one is it- the Vantage or the NVidia AI one? Can you send an EXR so we can examine the render elements to possibly see what's causing this? If that doesn't help may be it would be better to send us the scene for further debugging.

Best regards,
Alexander

[basafath21]

How do I check which Denoiser is being used?

[npg]

It's in Edit->Preferences->Render Defaults, but I'm pretty sure you're not using the Vantage denoiser, so this question isn't important. It's more important if we can get an EXR file to inspect some of the inputs the NVIDIA denoiser uses.

[Alexander.Atanasov]

You can check it from:
Edit menu -> Preferences -> Render Defaults (https://docs.chaosgroup.com/display/...refPreferences)

[npg]

We have identified the problem and we have implemented a fix. The issue occurs when using multiple GPUs, so until a new build is available, you can avoid it by disabling the second GPU from Edit->Render Devices (if you're using NVLink you will have to disable the link first).

[cole_maes]

I've been getting this issue since updating to the latest (unsupported by Vantage) GPU driver (471.68 ) and enabling the Combined Denoiser. I'm only using one 3090 GPU. I seem to get it on the first frame when rendering a sequence though and it's larger to begin with and reduces over time with more samples. All remaining frames tend to be fine.

[npg]

This is strange... Have you tried reverting to an older driver? The issue we found and solved is not related to the driver, it was in our code.

By the way, combined denoising is only used in interactive mode. If you start a high quality render it always uses the NVIDIA denoiser unless it is not available (e.g. when using a much older driver).