Cycles: Motion blur causing some frames to render objects incorrectly #95475

New Issue

Jon Tetrino · 2022-02-03T16:37:57+01:00

Jon Tetrino commented

2022-02-03 16:37:57 +01:00

System Information
Operating system: Windows-10-10.0.19044-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 3090/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 511.23

Blender Version
Broken: version: 3.0.1, branch: master, commit date: 2022-01-25 17:19, hash: dc2d180181
Broken: 2.9+ including 3.1 Beta

Short description of error
There is an issue when motion blur is enabled in render settings while using Cycles that results in some objects in scene having incorrect lighting and material properties for one or more frames.

None of the below errors occur with Motion Blur disabled.

If the frame is the first frame to be rendered, it will always render correctly. However if the frame is rendered after another, it will always fail. See steps.

I've seen this issue with numerous files, though the actual frame number that errors is seemingly random. I assumed it was my pipeline until another user I know found the same issue.

It might be related to objects being children of other objects in the scene hierarchy. It only seems to effect animated objects.

Exact steps for others to reproduce the error
I have attached a blend file. Note that Render settings have Motion Blur enabled with shutter length of 1. File is set to render with Optix. Export file type does not matter in this instance.

render_error_reproduction.blend

Render Frame #64 immediately after opening the file, do not make any changes, and view in Render Result. Observe that result should appear like so:

Render any other frame, then re-render #64. You will see one of these three results (full-black, full-bright, and no-object at all):
{F12843849}{F12843851}

If you change the render engine from GPU to CPU and re-render #64 it will succeed. However if you follow the above steps again, while on CPU rendering, the error will once again occur. If you then flip the render engine to GPU Optix again, the frame error will be magically fixed until you repeat the above steps once again.

Closing and re-opening the file allows you to re-render #64 correctly as long as it is the first file to render.

Oddly if you repeat these steps using CUDA instead of OPTIX., the object can disappear entirely and we'll also have other rendering artefacts.

Again none of this occurs with Motion Blur disabled.

While we can work around it by re-rendering specific frames it's a bit of a headache, especially when working with EXR output via command line that we can't easily preview on the fly. Post-process motion blur is also not a great solution for us.

**System Information** Operating system: Windows-10-10.0.19044-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 3090/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 511.23 **Blender Version** Broken: version: 3.0.1, branch: master, commit date: 2022-01-25 17:19, hash: `dc2d180181` Broken: 2.9+ including 3.1 Beta **Short description of error** There is an issue when motion blur is enabled in render settings while using Cycles that results in some objects in scene having incorrect lighting and material properties for one or more frames. None of the below errors occur with Motion Blur disabled. If the frame is the first frame to be rendered, it will always render correctly. However if the frame is rendered after another, it will always fail. See steps. I've seen this issue with numerous files, though the actual frame number that errors is seemingly random. I assumed it was my pipeline until another user I know found the same issue. It might be related to objects being children of other objects in the scene hierarchy. It only seems to effect animated objects. **Exact steps for others to reproduce the error** I have attached a blend file. Note that Render settings have Motion Blur enabled with shutter length of 1. File is set to render with Optix. Export file type does not matter in this instance. [render_error_reproduction.blend](https://archive.blender.org/developer/F12843902/render_error_reproduction.blend) Render Frame #64 immediately after opening the file, do not make any changes, and view in Render Result. Observe that result should appear like so:![material_working.png](https://archive.blender.org/developer/F12843847/material_working.png) Render any other frame, then re-render #64. You will see one of these three results (full-black, full-bright, and no-object at all): {[F12843849](https://archive.blender.org/developer/F12843849/no_material.png)}{[F12843851](https://archive.blender.org/developer/F12843851/fullbright.png)}![no_object.png](https://archive.blender.org/developer/F12843866/no_object.png) If you change the render engine from GPU to CPU and re-render #64 it will succeed. However if you follow the above steps again, while on CPU rendering, the error will once again occur. If you then flip the render engine to GPU Optix again, the frame error will be magically fixed until you repeat the above steps once again. Closing and re-opening the file allows you to re-render #64 correctly as long as it is the first file to render. Oddly if you repeat these steps using CUDA instead of OPTIX., the object can disappear entirely and we'll also have other rendering artefacts. Again none of this occurs with Motion Blur disabled. While we can work around it by re-rendering specific frames it's a bit of a headache, especially when working with EXR output via command line that we can't easily preview on the fly. Post-process motion blur is also not a great solution for us.

Jon Tetrino commented

2022-02-03 16:37:58 +01:00

Added subscriber: @Tetrino

Jon Tetrino changed title from ~~Motion blur causing some frames to render objects incorrectly~~ to Cycles: Motion blur causing some frames to render objects incorrectly

2022-02-03 16:40:42 +01:00

Steffen Dünner commented

2022-02-03 16:48:34 +01:00

Added subscriber: @SteffenD

Steffen Dünner commented

2022-02-03 16:48:34 +01:00

Sounds a lot like a problem with "Persistent Data" on:

Sounds a lot like a problem with "Persistent Data" on: ![image.png](https://archive.blender.org/developer/F12843929/image.png)

Jon Tetrino commented

2022-02-03 17:13:52 +01:00

Huh, @SteffenD you are entirely correct, I didn't even consider it - is it a known issue?

Richard Antalik commented

2022-02-04 05:43:59 +01:00

Changed status from 'Needs Triage' to: 'Confirmed'

Atair-1 commented

2022-02-12 17:39:21 +01:00

Added subscriber: @Atair-1

Atair-1 commented

2022-02-12 17:39:21 +01:00

GPU, Nvidia, Optix, Blender 3.0.1

having the same issue - can't share any screens or files, but it involves large scale objects (planets) and small objects (satellites). The planets are 100x smaller to avoid too big issues with the bvh, still after some time problems emerge with persistent data on.
Somehow the bvh gets corrupted? or is not properly built?
All of the above only when motion blur is enabled..
Is there any workaround? because reloading several 20k earth maps per frame is not fun

GPU, Nvidia, Optix, Blender 3.0.1 having the same issue - can't share any screens or files, but it involves large scale objects (planets) and small objects (satellites). The planets are 100x smaller to avoid too big issues with the bvh, still after some time problems emerge with persistent data on. Somehow the bvh gets corrupted? or is not properly built? All of the above only when motion blur is enabled.. Is there any workaround? because reloading several 20k earth maps per frame is not fun

Brecht Van Lommel commented

2022-05-10 21:04:29 +02:00

Added subscriber: @brecht

Brecht Van Lommel commented

2022-05-10 21:04:29 +02:00

Changed status from 'Confirmed' to: 'Resolved'

Brecht Van Lommel closed this issue

2022-05-10 21:04:29 +02:00

Brecht Van Lommel self-assigned this 2022-05-10 21:04:29 +02:00

Brecht Van Lommel commented

2022-05-10 21:04:29 +02:00

Appears to be fixed by 94205e1.

Appears to be fixed by 94205e1.

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Cycles: Motion blur causing some frames to render objects incorrectly #95475