Cycles- Strange results and exceptionally long render time that affects only a few frames if motion blur is enabled in combination with geo node particles. #111331

New Issue

michael campbell · 2023-08-20T20:56:35+02:00

michael campbell commented

2023-08-20 20:56:35 +02:00

System Information
Operating system: Windows-10-10.0.19044-SP0 64 Bits
Graphics card: NVIDIA GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 536.99

Blender Version
Broken: version: 3.6.1, branch: blender-v3.6-release, commit date: 2023-07-17 12:50, hash: 8bda729ef4dc
Worked: (newest version of Blender that worked as expected)

Short description of error
Weird results and extreme render time of a couple of frames without any seemingly obvious reason. See end of attached animation. Problem goes away if motion blur is disabled, but it doesn't seem to be a general motion blur incompatibility with Geo Nodes particles, because all other frames are fine.

Exact steps for others to reproduce the error
download blend file: https://www.dropbox.com/scl/fi/6up2o2k7tj13wvzqhmcf3/rendering-bug-with-geo-nodes.blend?rlkey=z5eemjp9kqkrmhh0m1kbzk731&dl=0

open file
render the animation (only 4 frames). Frame 87 and 90 are fine, frame 88 and 89 take a long time and produce very odd results.

The geo nodes scatter particles on the mesh and then transfer the colours to the particles. This is all working find apart from those couple of frames. This is extremely odd, because at this point the particles are not being displaced at all and neither were they on the previous frame...so I'm not sure why having motion blur enabled would cause the error.

The viewport is fine throughout, but here's the final render results

Alpha on frame 87

Alpha on frame 88 (there are no particles in the areas where the alpha is weird)

Combined pass frame 87 - correct result

Combined pass frame 88 - strange result

**System Information** Operating system: Windows-10-10.0.19044-SP0 64 Bits Graphics card: NVIDIA GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 536.99 **Blender Version** Broken: version: 3.6.1, branch: blender-v3.6-release, commit date: 2023-07-17 12:50, hash: `8bda729ef4dc` Worked: (newest version of Blender that worked as expected) **Short description of error** Weird results and extreme render time of a couple of frames without any seemingly obvious reason. See end of attached animation. Problem goes away if motion blur is disabled, but it doesn't seem to be a general motion blur incompatibility with Geo Nodes particles, because all other frames are fine. **Exact steps for others to reproduce the error** download blend file: https://www.dropbox.com/scl/fi/6up2o2k7tj13wvzqhmcf3/rendering-bug-with-geo-nodes.blend?rlkey=z5eemjp9kqkrmhh0m1kbzk731&dl=0 open file render the animation (only 4 frames). Frame 87 and 90 are fine, frame 88 and 89 take a long time and produce very odd results. The geo nodes scatter particles on the mesh and then transfer the colours to the particles. This is all working find apart from those couple of frames. This is extremely odd, because at this point the particles are not being displaced at all and neither were they on the previous frame...so I'm not sure why having motion blur enabled would cause the error. The viewport is fine throughout, but here's the final render results Alpha on frame 87 ![image](/attachments/025e7e22-2ab8-4340-b014-cd1f5c80d7ff) Alpha on frame 88 (there are no particles in the areas where the alpha is weird) ![image](/attachments/0746b6d2-b5f8-4d14-ab95-bfa70dd6d4cb) Combined pass frame 87 - correct result ![image](/attachments/dbd2d725-e02f-4f21-a8b5-43f0e4052c56) Combined pass frame 88 - strange result ![image](/attachments/0e741401-4da8-487b-8cdf-1b0d3a102ce0)

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michael campbell added the

labels 2023-08-20 20:56:35 +02:00

michael campbell changed title from ~~Strange results and exceptionally long render time when using geo node created attributes with Cycles~~ to Cycles- Strange results and exceptionally long render time that affects only a few frames if motion blur is enabled in combination with geo node particles.

2023-08-20 21:08:39 +02:00

michael campbell commented

2023-08-20 22:53:56 +02:00

I've just checked and the points have the same ID's and positions either side of the frames that are rendering incorrectly. So it cant be caused by moving particles/ID's.