Maniphest T91487

Persistent Data & Motion Blur cause some frames to look weird when rendering animation in Cycles
Closed, DuplicateBUG
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Assigned To
None
Authored By
vincent (Gyoo18)
Sep 17 2021, 4:20 PM
Tags
  • BF Blender
  • Render & Cycles
Subscribers
Alaska (Alaska)
Brecht Van Lommel (brecht)
Philipp Oeser (lichtwerk)
poq poq (poqpoq)
vincent (Gyoo18)

Description

System Information
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: GeForce RTX 2060/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 462.31

System Information (@Alaska (Alaska)):
Operating system: Linux-5.10.0-8-amd64-x86_64-with-glibc2.31 64 Bits
Graphics card: NVIDIA GeForce RTX 3090/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 470.63.01

Blender Version:
Broken version: 2.93.4, branch: master, commit date: 2021-08-31 09:23, hash: rBb7205031cec4
Broken version: 3.0.0 Alpha, branch: master, commit date: 2021-09-18 19:45, hash: rBbdbc7e12a02e
Worked: Unsure

Short description of error:
I've been Rendering a 3000 frames animation and some frames look like this:


or this:

@Alaska (Alaska) :
Upon further investigation it seems that the cause for this issue is a combination of Persistent Data, Motion Blur, and the rotation of the object which is causing this issue. If Persistent Data is off, the issue goes away. If Motion Blur is off, the issue goes away. If the rotation animation is removed from the affected objects, then the issue goes away.

Exact steps for others to reproduce the error:
Take one of these files and render out the animation and look at the final frames:

GRYC_Problem.blend78 MBDownload

T91487 - Simplified Scene.blend839 KBDownload

T91487 - Simplified Scene - 2.blend846 KBDownload

Steps to reproduce are as follows accord to @Alaska (Alaska)

  1. Create a scene with an object.
  2. Enable Auto key frames.
  3. Select the object and press Play on the timeline.
  4. Start rotating the object by press R and moving your mouse, then take a short pause (half a second maybe), then move your mouse again to rotate again. Keep doing this until you're at the end of the time line.
  5. Render the scene in Cycles with Persistent Data and Motion Blur enabled and observe that some frames have artifacts, generally when rotation starts.

Related Objects

Event Timeline

vincent (Gyoo18) created this task.Sep 17 2021, 4:20 PM
Alaska (Alaska) changed the task status from Needs Triage to Needs Information from User.Sep 18 2021, 12:30 AM
Alaska (Alaska) added a subscriber: Alaska (Alaska).

Without steps to reproduce the issue, or a scene to test with, it is hard for us to triage this report and to find the bug. If you can provide steps or the scene, please do.

As a side note, are you able to test the Cycles-X branch of Blender? It may contain fix for your issues. https://builder.blender.org/download/experimental/ (Download the one with Cycles-X in the name)

vincent (Gyoo18) added a comment.Sep 18 2021, 4:38 AM

I Will try on Cycles-X.

vincent (Gyoo18) added a comment.Sep 19 2021, 4:34 AM

I have managed to reduce the file size while keeping the bug, so here's the file:

GRYC_Problem.blend78 MBDownload

Just open, make sure to know the render animation directory is, open that directory in the file explorer (not the blender one) and hit render animation. Just keep an eye on the frames if you don't want to render the whole thing and you should see a weird frame somewhere.

Alaska (Alaska) changed the task status from Needs Information from User to Confirmed.EditedSep 19 2021, 6:28 AM
Alaska (Alaska) changed the subtype of this task from "Report" to "Bug".
Alaska (Alaska) added a project: Render & Cycles.
Alaska (Alaska) added a subscriber: Brecht Van Lommel (brecht).

CC @Brecht Van Lommel (brecht) as this appears to be a issue with Persistent Data and you seem the most knowledgeable in this area.

I can confirm that rendering artifacts occur while rendering this animation. Rendering single frames does not show the issue.

The issue is present in Master and Cycles-X at the time of writing.

The cause, from my testing, is to do with how the Persistent Data option is interacting with Motion Blur on the objects in the scene. If you disable either Persistent Data or Motion Blur the issue goes away.

I also decided to do some further testing and the issue seems to be caused by rotation. If you isolate Cube.025 (The main part of the boat) for rendering then clear the keyframes for rotation, then the issue goes away. If you leave the keyframes for rotation, then the issue remains.
And it seems to be just the rotation animation. Because substituting another object in place of Cube.025 with the same animation gives the same issues.

However, I'm not sure why this specific animation is causing issues.

Here's a simplified file: It's a fresh scene with a cube with the rotational animation data from Cube.025 with Persistent Data and Motion Blur enabled with samples and resolution reduced for fast rendering.

T91487 - Simplified Scene.blend839 KBDownload

It produces issues like these:

Good FrameBad Frame

I was also able to replicate it from scratch by following these steps:

  1. Create a scene.
  2. Enable Auto key frames.
  3. Select the cube and press Play on the timeline.
  4. Start rotating the cube by press R and move your mouse, then take a short pause (fraction of a second), then move your mouse again to rotate again. Keep doing this until you're at the end of the time line.
  5. Render the scene in Cycles with Persistent Data and Motion Blur enabled and observe that some frames have artifacts.

Here's that file:

T91487 - Simplified Scene - 2.blend846 KBDownload

System Information
Operating system: Linux-5.10.0-8-amd64-x86_64-with-glibc2.31 64 Bits
Graphics card: NVIDIA GeForce RTX 3090/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 470.63.01

Blender Version
Broken: version: 3.0.0 Alpha, branch: master, commit date: 2021-09-18 19:45, hash: rBbdbc7e12a02e

Alaska (Alaska) updated the task description.Sep 19 2021, 6:35 AM
Alaska (Alaska) updated the task description.Sep 20 2021, 1:18 AM
Philipp Oeser (lichtwerk) renamed this task from Some frames look weird when rendering animation in Cycles to Persistent Data & Motion Blur cause some frames to look weird when rendering animation in Cycles.Feb 4 2022, 9:42 AM
poq poq (poqpoq) added a subscriber: poq poq (poqpoq).Feb 18 2022, 4:49 AM
Lt Knb (Lt-knb) mentioned this in T96822: Persistent Data Causes Render Errors for Motion Blur.Mar 28 2022, 7:22 PM
Philipp Oeser (lichtwerk) added a subscriber: Philipp Oeser (lichtwerk).Apr 6 2022, 5:13 PM

There is now a very clear repro case in T96822: Persistent Data Causes Render Errors for Motion Blur, will merge these reports

Philipp Oeser (lichtwerk) closed this task as a duplicate of T96822: Persistent Data Causes Render Errors for Motion Blur.Apr 6 2022, 5:13 PM