Cycles materials will occasionally turn black in the viewport when deforming meshes #115092

New Issue

Dvorakir · 2023-11-18T14:27:48+01:00

Dvorakir commented

2023-11-18 14:27:48 +01:00

System Information
Operating system: Windows-10-10.0.19045-SP0 64 Bits
Graphics card: NVIDIA GeForce GTX 1070 Ti/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 537.34
Also tested:
Graphics card: NVIDIA GeForce RTX 2060/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 536.40

Blender Version
Broken: version: 4.0.0, branch: blender-v4.0-release, commit date: 2023-11-13 17:26, hash: 878f71061b8e
Has been an issue for a long time, first ran into it in Blender 2.92

Short description of error
When deforming meshes with an armature (e.g. posing or playing an animation) and using cycles in the viewport, some materials will turn black.
Sometimes this is temporary and the materials return less than a second later, but the rest of the time the materials will remain black until the viewport is set to a different shading mode and back to cycles.

I've occasionally run into this issue for two years now, but I think I found the conditions for the issue to happen:
It seems to only happen to materials that exist on two (or more) meshes that are both being deformed by an armature.
The bug is not limited to GPU Compute, I've also observed the issue when using just CPU rendering

Exact steps for others to reproduce the error

open the attached .blend
set viewport to Rendered shading (cycles)
hit play

The character is split into two meshes, and an animation rotates the hip bone.
After a while the material will turn black, and potentially back again.
If nothing happens for a long while, setting the viewport to Solid and back to Rendered (cycles) might help

example 1	example 2

**System Information** Operating system: Windows-10-10.0.19045-SP0 64 Bits Graphics card: NVIDIA GeForce GTX 1070 Ti/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 537.34 Also tested: Graphics card: NVIDIA GeForce RTX 2060/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 536.40 **Blender Version** Broken: version: 4.0.0, branch: blender-v4.0-release, commit date: 2023-11-13 17:26, hash: `878f71061b8e` Has been an issue for a long time, first ran into it in Blender 2.92 **Short description of error** When deforming meshes with an armature (e.g. posing or playing an animation) and using cycles in the viewport, some materials will turn black. Sometimes this is temporary and the materials return less than a second later, but the rest of the time the materials will remain black until the viewport is set to a different shading mode and back to cycles. I've occasionally run into this issue for two years now, but I think I found the conditions for the issue to happen: It seems to only happen to materials that exist on two (or more) meshes that are both being deformed by an armature. The bug is not limited to GPU Compute, I've also observed the issue when using just CPU rendering **Exact steps for others to reproduce the error** 1. open the attached .blend 2. set viewport to Rendered shading (cycles) 3. hit play The character is split into two meshes, and an animation rotates the hip bone. After a while the material will turn black, and potentially back again. If nothing happens for a long while, setting the viewport to Solid and back to Rendered (cycles) might help | example 1 | example 2 | | -- | -- | | <video src="/attachments/cdb9a04a-b4a3-48a3-acbe-fa17c5d46ce4" title="m1.mp4" controls></video> | <video src="/attachments/41afef20-93c2-4439-9547-ddef196eb2a4" title="m2.mp4" controls></video> |

materialposebug.blend

996 KiB

m1.mp4

2.1 MiB

m2.mp4

6.5 MiB

Dvorakir added the

labels 2023-11-18 14:27:48 +01:00

Ian Failing commented

2023-11-20 02:43:04 +01:00

I got it to reproduce exactly once 😣

System Information
Operating system: Windows-10-10.0.23590-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 4090/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 550.09

Blender Version
Broken: version: 4.0.1, branch: blender-v4.0-release, commit date: 2023-11-16 16:40, hash: d0dd92834a08
Worked: (newest version of Blender that worked as expected)

I got it to reproduce exactly once 😣 **System Information** Operating system: Windows-10-10.0.23590-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 4090/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 550.09 **Blender Version** Broken: version: 4.0.1, branch: blender-v4.0-release, commit date: 2023-11-16 16:40, hash: `d0dd92834a08` Worked: (newest version of Blender that worked as expected)

Iliya Katushenock added

and removed

labels 2023-11-20 11:32:58 +01:00

Dvorakir commented

2023-11-21 18:46:04 +01:00

I tried to reproduce it on a system with a RTX 3080 but after many tries the issue still didn't occur - seems like the issue is more likely on weaker systems

philovivero commented

2024-01-29 16:35:42 +01:00

For the record, as of 29 Jan 2024, I am seeing this problem, too. Except I see it on objects that do not have any deform on them. Just regular old objects that are parented to vertexes on the mesh.

My system: Blender 4.0.2, Mac Studio M2, native arm64 version. So it seems "weaker systems" is a poor hypothesis. And it seems to happen across many types of systems, leading me to believe the bug is in Cycles itself, not some rendering subsystem after Cycles.

The description matches what I see, but I will repeat for clarity/completeness.

In one animation, I had a character with eyes that would go from their normal colour to black and back again. The material broken-ness will last for maybe 60-300 frames. In another animation, the eyes were fine for the whole animation, but one jewel would go from coloured to black and back again.

In the animation where the eyes would go black and back again, both eyes would go to black, so it seems it has something to do with the material and all objects that share that material will suffer the same problem with the bug manifests itself.

Reproducing seems very difficult as it is intermittent and when I notice it, it's almost always toward the end of a multi-minute animation. I am willing to do experiments if the developers would like to test hunches about where the bug might be, but I suspect the attached .blend and MP4 files to the original bug report are demonstrating the bug as I experience it.

For the record, as of 29 Jan 2024, I am seeing this problem, too. Except I see it on objects that do not have any deform on them. Just regular old objects that are parented to vertexes on the mesh. My system: Blender 4.0.2, Mac Studio M2, native arm64 version. So it seems "weaker systems" is a poor hypothesis. And it seems to happen across many types of systems, leading me to believe the bug is in Cycles itself, not some rendering subsystem after Cycles. The description matches what I see, but I will repeat for clarity/completeness. In one animation, I had a character with eyes that would go from their normal colour to black and back again. The material broken-ness will last for maybe 60-300 frames. In another animation, the eyes were fine for the whole animation, but one jewel would go from coloured to black and back again. In the animation where the eyes would go black and back again, both eyes would go to black, so it seems it has something to do with the material and all objects that share that material will suffer the same problem with the bug manifests itself. Reproducing seems very difficult as it is intermittent and when I notice it, it's almost always toward the end of a multi-minute animation. I am willing to do experiments if the developers would like to test hunches about where the bug might be, but I suspect the attached .blend and MP4 files to the original bug report are demonstrating the bug as I experience it.

philovivero commented

2024-01-29 19:26:28 +01:00

I will probably experiment a bit with this setting, since it seems a potential culprit to me at the moment. This setting is unchecked/off by default, and I have it checked/on.

The original topic blendfile does not have that setting checked/enabled, though, so it might not be so relevant.

I will probably experiment a bit with this setting, since it seems a potential culprit to me at the moment. This setting is unchecked/off by default, and I have it checked/on. The original topic blendfile does not have that setting checked/enabled, though, so it might not be so relevant.

Screenshot 2024-01-29 at 12.21.27 PM.png

5.7 KiB

philovivero commented

2024-01-29 19:33:32 +01:00

FWIW I am able to repro on 4.0.2 on Mac using arm64 binary. Loaded it up, made a tiny window, pressed spacebar then after a few frames, boom. Black.

FWIW I am able to repro on 4.0.2 on Mac using arm64 binary. Loaded it up, made a tiny window, pressed `spacebar` then after a few frames, boom. Black.

Screenshot 2024-01-29 at 12.32.29 PM.png

70 KiB

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Cycles materials will occasionally turn black in the viewport when deforming meshes #115092