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(v2.82+, CYCLES) Rendering with motion blur enabled causing unexpected, broken-looking result on specific frames
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Description

System Information
Operating system: MacOS 10.14.6
Graphics card: Intel Iris Pro 1536 MB{F8557214}

Blender Version
Broken: version: 2.82 (sub 7), branch: master, commit date: 2020-03-12 05:06, hash: rB375c7dc4caf4
Broken: 2.83 (sub 17), branch: master, commit date: 2020-05-15 17:29, hash: rBe5ace51295b9
Worked: v2.80 Beta branch: blender 2.7, commit date: 2019-02-08 04:22, hash: 46ac288a9306

Issue:
(Cycles) Rendering with Motion Blur enabled in the Render Properties Tab causes unexpected, broken-looking result. Starting on frame 17, the final render will either display as simple "glitch"-looking image (flat grey and purple jagged shapes), or Blender may abruptly crash while rendering frame 17. If Motion Blur is toggled off, the final render yields the expected result.


Exact steps for others to reproduce the error

  1. Open motionBlurIssue.blend in v2.82. Viewport should display model of a purple cassette tape.
  2. Ensure Motion Blur is enabled in Render Properties Tab.
  3. Render animation frames 16-20, format: FFmpeg video, container type: MPEG-4
  4. Observe that starting on frame 17, the resulting render is "glitchy" broken-looking image inconsistent with contents of the 3d viewport.

4a. Disable motion blur and repeat steps 3 & 4 to observe expected results consistent with 3D viewport.

Thank you. The attached file is one section of a longer animation. This issue is occurring on multiple frames throughout the duration of the animation only when motion blur is enabled. The rate at which rendering the animation in this file results in a Blender crash, for me, is about 40%.

Attaching screenshot of "broken" frame 17 render result:

Event Timeline

Alaska (Alaska) changed the task status from Needs Triage to Confirmed.EditedMay 27 2020, 12:30 PM
Alaska (Alaska) added a subscriber: Alaska (Alaska).

I am able to reproduce the issue on Linux-5.4.0-7629-generic-x86_64-with-debian-bullseye when rendering with a CPU (Ryzen 9 3900X) or a GPU GTX 1050Ti (CUDA) with Blender 2.90 rBeb5422828ac1 (2020-05-26 20:02) . OptiX (Cycles_Optix_Test=1) does not show these issues.

Alaska (Alaska) added a comment.EditedMay 27 2020, 12:35 PM

Seems to be similar to T75441 as an object changes it's scale from something to 0 on frame 17. I will leave the decision up to the developers and other moderators on whether these issues are similar enough to merge.

Actually, doing more investigation. I'm 95% confident these are the same issue. Merging the tasks.

@Kash Barr (KashBarr) as a work around in the meantime, you can hide the objects you no longer want on frame 17 rather than scaling it to 0. This can be done by keyframing this option:

You will need to do this for each individual object, not just the empty that's used to control the scale of the object.

Thanks @Alaska (Alaska) will give your solution a shot.