VRay NEXT GPU + Camera Motion Blur = Black spots

[D3Pixel]

Hi

I have a scene with a small object that uses a VRay Standard material (metal), also a VRayEdgeTex as bump and for some reason Motion Blur enabled on the camera creates small black smudges on just that object. This is rendering on the GPU. Any ideas? Brute Force or Light Cache does not remove it. Increasing Motion blur samples (Object->Vray Properties) does not remove it. I just could not find a setting that removed this small black smudge of pixels on the object. Disable Motion Blur on the camera is the only thing that removes the black smudge.

I have decided to still render out the animation and heal brush every frame (about 60 of them) to get rid of it but it's not the most ideal solution. I could do a Vector pass I suppose but vanilla After Effects is naff with VRay Vector passes.

Thanks for any tips.

[Miro]

Hi,

Can you share the scene to support@chaosgroup.com so we can check it out? Also which V-Ray version are you using and do these artifacts appear if you run the render on the CPU?

[JFichtmueller]

Hi,
Any news on this problem? I'm having a similar issue and would appreciate any help.
I'm using GPU Next, update 1.1 and the problem occurs regardless of using GPU or CPU on 3 different machines.

[D3Pixel]

Hmm, going back to that issue I think I just manually fixed every frame but also found that the free version of Fusion works great with Motion Vector Passes so that is a possible solution if you are stuck.

[vlado]

Hi,
Any news on this problem? I'm having a similar issue and would appreciate any help.
I'm using GPU Next, update 1.1 and the problem occurs regardless of using GPU or CPU on 3 different machines.

Can you show me what it looks like?

Best regards,
Vlado

[JFichtmueller]

Hmm, going back to that issue I think I just manually fixed every frame but also found that the free version of Fusion works great with Motion Vector Passes so that is a possible solution if you are stuck.

Yeah that's of course possible as well. I could also use the After Effects RSMB plug-in. But I'd really prefer 3D-rendered motion blur since it's finally affordable with V-Ray-GPU. And it's also only on a couple of frames in one of many sequences. I render out the area with V-Ray Next (former Adv.) for now, which doesn't produce the artifact. But it's much slower of course.

I attached you an image of the issue, Vlado. The problem occurs only in GPU Next (on Cuda devices as well as processors) and only whith motion blur turned on. Also it only appears on a couple of seemingly random frames in only one of several sequences rendered out from the same secene. But in those frames the artifact will always appear and look the same each time the frame is rendered. It's only on one object, but will appear in different areas in the different frames.
What's interesting is, that it changes how it looks, depending on if refraction is turned off or on. You can even see it in the different passes: With refraction on, the artifact switches from darkening the pixels down to brighten them up in the lighting pass.

Edit: Also, it won't appear, when the object is isolated and rendered.

Let me know if you need additional information, and thanks for helping me out!