As motion blur steps increase, OptiX deviates from CUDA and CPU rendering in high motion blur scenes. #81315

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opened 2020-09-30 07:10:49 +02:00 by Alaska · 13 comments
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System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: RTX 2060 SUPER 456.38

Blender Version
Broken: version: 2.81, 2.82, 2.83.6, 2.90.1, 2.91.0 Alpha e5aa9decb2 2020-09-29 22:41
Worked: NA

Short description of error
When the motion blur steps of a fast moving object is increased and the scene has motion blur enabled, the OptiX backend renderer for Cycles will start to produce significantly different results from other rendering backends like CUDA and CPU rendering. Here's some example images:

CPU/CUDA OptiX
CPU-CUDA.jpg OptiX.jpg

Exact steps for others to reproduce the error

  1. Switch the render engine to Cycles and enable motion blur.
  2. Create a scene where an object moves quickly across the camera's view. (E.G. A cube traveling the entire camera view in one frame)
  3. Select the object and in the Object tab of the Properties panel, increase the Steps value in the Motion blur section to a higher value such as 5.
  4. Render out the frame where the object shows motion blur with your CPU or GPU with CUDA (unsure about OpenCL) and compare it to the results from OptiX. Notice the difference.

I have provided a .blend file with steps 1-3 complete. All that needs to be done is frame 2 needs to be rendered.
#81315 - OptiX motion blur inconsistency.blend

**System Information** Operating system: Windows-10-10.0.19041-SP0 64 Bits Graphics card: RTX 2060 SUPER 456.38 **Blender Version** Broken: version: 2.81, 2.82, 2.83.6, 2.90.1, 2.91.0 Alpha `e5aa9decb2` 2020-09-29 22:41 Worked: NA **Short description of error** When the motion blur steps of a fast moving object is increased and the scene has motion blur enabled, the OptiX backend renderer for Cycles will start to produce significantly different results from other rendering backends like CUDA and CPU rendering. Here's some example images: | CPU/CUDA |OptiX| | -- | -- | |![CPU-CUDA.jpg](https://archive.blender.org/developer/F8938828/CPU-CUDA.jpg)|![OptiX.jpg](https://archive.blender.org/developer/F8938830/OptiX.jpg)| **Exact steps for others to reproduce the error** 1. Switch the render engine to Cycles and enable motion blur. 2. Create a scene where an object moves quickly across the camera's view. (E.G. A cube traveling the entire camera view in one frame) 3. Select the object and in the `Object` tab of the `Properties panel`, increase the `Steps` value in the `Motion blur` section to a higher value such as 5. 4. Render out the frame where the object shows motion blur with your CPU or GPU with CUDA (unsure about OpenCL) and compare it to the results from OptiX. Notice the difference. I have provided a .blend file with steps 1-3 complete. All that needs to be done is frame 2 needs to be rendered. [#81315 - OptiX motion blur inconsistency.blend](https://archive.blender.org/developer/F8938837/T81315_-_OptiX_motion_blur_inconsistency.blend)
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Added subscriber: @Alaska

Added subscriber: @Alaska

Added subscriber: @bent

Added subscriber: @bent
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Added subscribers: @pmoursnv, @lichtwerk

Added subscribers: @pmoursnv, @lichtwerk
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Changed status from 'Needs Triage' to: 'Needs Developer To Reproduce'

Changed status from 'Needs Triage' to: 'Needs Developer To Reproduce'
Member

Hi @Alaska

I cannot reproduce (but that might very well be because I am using Optix on a 970m)

**System Information**
Operating system: Linux-5.8.4-200.fc32.x86_64-x86_64-with-fedora-32-Thirty_Two 64 Bits
Graphics card: GeForce GTX 970M/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 450.66
version: 2.91.0 Alpha, branch: master, commit date: 2020-10-11 22:38, hash: `rBdf3d124e9104`

Is this still an issue with the latest Alpha?

@pmoursnv : does this ring a bell?

Hi @Alaska I cannot reproduce (but that might very well be because I am using Optix on a 970m) ``` **System Information** Operating system: Linux-5.8.4-200.fc32.x86_64-x86_64-with-fedora-32-Thirty_Two 64 Bits Graphics card: GeForce GTX 970M/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 450.66 version: 2.91.0 Alpha, branch: master, commit date: 2020-10-11 22:38, hash: `rBdf3d124e9104` ``` Is this still an issue with the latest Alpha? @pmoursnv : does this ring a bell?
Patrick Mours self-assigned this 2020-10-14 18:01:46 +02:00
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Changed status from 'Needs Developer To Reproduce' to: 'Confirmed'

Changed status from 'Needs Developer To Reproduce' to: 'Confirmed'
Member

Can reproduce, investigating.

Can reproduce, investigating.
Member

Thx checking @pmoursnv!
Guess we can call this a bug then?

Thx checking @pmoursnv! Guess we can call this a bug then?
Member

Is a driver bug (hence why it didn't reproduce on r450 too). I will update this thread once a new driver with a fix is published.

Is a driver bug (hence why it didn't reproduce on r450 too). I will update this thread once a new driver with a fix is published.
Author
Member

In #81315#1035637, @pmoursnv wrote:
Is a driver bug (hence why it didn't reproduce on r450 too). I will update this thread once a new driver with a fix is published.

Using drivers 457.30 on Windows I'm personally unable to reproduce this anymore. Can you confirm @pmoursnv ?

> In #81315#1035637, @pmoursnv wrote: > Is a driver bug (hence why it didn't reproduce on r450 too). I will update this thread once a new driver with a fix is published. Using drivers 457.30 on Windows I'm personally unable to reproduce this anymore. Can you confirm @pmoursnv ?
Member

Yes, was about to notify. The fix is in 457.30 (Windows Studio driver) and 455.45.01 (Linux).

Yes, was about to notify. The fix is in 457.30 (Windows Studio driver) and 455.45.01 (Linux).
Member

Changed status from 'Confirmed' to: 'Resolved'

Changed status from 'Confirmed' to: 'Resolved'

Added subscriber: @thechode

Added subscriber: @thechode
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Reference: blender/blender#81315
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