Artefacts appear when ambient occlusion (AO) is enabled #93346

New Issue

Rujul Arora · 2021-11-24T08:39:02+01:00

Rujul Arora commented

2021-11-24 08:39:02 +01:00

System Information
Operating system: Windows-10-10.0.19043-SP0 64 Bits
Graphics card: NVIDIA GeForce GTX 1050 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 466.63

Blender Version
Broken: version: 3.1.0 Alpha, branch: master, commit date: 2021-11-22 23:57, hash: d1a4e043bd
Worked: N/A

Short description of error
I use AO for all my textures. When I render out models in Cycles with those AO textures, sometimes I see these artefacts on the model caused by the AO (I know they are caused by the AO because they do not appear when I turn it off, and the colour of the artefacts depends on the colour of the AO). The artefacts do not follow any edges or vertices, and they seem to decrease (though not disappear) when more topology is added (for example, when the model is bevelled or a subsurf modifier is used). Strangely, the artefacts tend to change or even completely disappear when their position is changed in the model (so there isn't any other mesh occluding the model, nor is it a topology issue). The issue may or may not persist when the model is taken to a different file.

Exact steps for others to reproduce the error

Open the attached .blend file.
Switch to 'rendered' view mode in Cycles.

BGRep.blend

**System Information** Operating system: Windows-10-10.0.19043-SP0 64 Bits Graphics card: NVIDIA GeForce GTX 1050 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 466.63 **Blender Version** Broken: version: 3.1.0 Alpha, branch: master, commit date: 2021-11-22 23:57, hash: `d1a4e043bd` Worked: N/A **Short description of error** I use AO for all my textures. When I render out models in Cycles with those AO textures, sometimes I see these artefacts on the model caused by the AO (I know they are caused by the AO because they do not appear when I turn it off, and the colour of the artefacts depends on the colour of the AO). The artefacts do not follow any edges or vertices, and they seem to decrease (though not disappear) when more topology is added (for example, when the model is bevelled or a subsurf modifier is used). Strangely, the artefacts tend to change or even completely disappear when their position is changed in the model (so there isn't any other mesh occluding the model, nor is it a topology issue). The issue may or may not persist when the model is taken to a different file. **Exact steps for others to reproduce the error** 1. Open the attached .blend file. 2. Switch to 'rendered' view mode in Cycles. [BGRep.blend](https://archive.blender.org/developer/F11962715/BGRep.blend) ![Screenshot (713).png](https://archive.blender.org/developer/F11962762/Screenshot__713_.png) ![Screenshot (714).png](https://archive.blender.org/developer/F11962777/Screenshot__714_.png) ![Screenshot (717).png](https://archive.blender.org/developer/F11962809/Screenshot__717_.png) ![Screenshot (716).png](https://archive.blender.org/developer/F11962833/Screenshot__716_.png) ![Screenshot (718).png](https://archive.blender.org/developer/F11962848/Screenshot__718_.png) ![Screenshot (706).png](https://archive.blender.org/developer/F11962900/Screenshot__706_.png) ![Screenshot (707).png](https://archive.blender.org/developer/F11962929/Screenshot__707_.png)

Rujul Arora commented

2021-11-24 08:39:02 +01:00

Added subscriber: @sharukh345

Alaska commented

2021-11-24 09:54:46 +01:00

Added subscriber: @Alaska

Alaska commented

2021-11-24 09:54:46 +01:00

Changed status from 'Needs Triage' to: 'Confirmed'

Alaska commented

2021-11-24 09:54:46 +01:00

I can confirm in Blender 3.1.0 and Blender 2.93 (I didn't test any others)

Turning off "Smooth Shading" resolves the issue.

I can confirm in Blender 3.1.0 and Blender 2.93 (I didn't test any others) Turning off "Smooth Shading" resolves the issue.

Rujul Arora commented

2021-11-25 10:21:04 +01:00

In #93346#1259168, @Alaska wrote:
I can confirm in Blender 3.1.0 and Blender 2.93 (I didn't test any others)

Turning off "Smooth Shading" resolves the issue.

Thank you! Another interesting thing I've noticed, the issue only appears when the mesh is away from the centre of the world. When it's near the centre, the issue resolves by itself. By the way, I do need shade smooth for the model.

> In #93346#1259168, @Alaska wrote: > I can confirm in Blender 3.1.0 and Blender 2.93 (I didn't test any others) > > Turning off "Smooth Shading" resolves the issue. Thank you! Another interesting thing I've noticed, the issue only appears when the mesh is away from the centre of the world. When it's near the centre, the issue resolves by itself. By the way, I do need shade smooth for the model.

Alaska commented

2021-11-25 12:16:59 +01:00

In #93346#1259781, @sharukh345 wrote:
Another interesting thing I've noticed, the issue only appears when the mesh is away from the centre of the world. When it's near the centre, the issue resolves by itself.

This indicates a precision issue. D12954: Removing ray offestting attempts to address issues like this. And testing that patch does indeed resolve the issue for me. The patch will probably be implemented into Blender 3.1.

> In #93346#1259781, @sharukh345 wrote: >Another interesting thing I've noticed, the issue only appears when the mesh is away from the centre of the world. When it's near the centre, the issue resolves by itself. This indicates a precision issue. [D12954: Removing ray offestting](https://archive.blender.org/developer/D12954) attempts to address issues like this. And testing that patch does indeed resolve the issue for me. The patch will probably be implemented into Blender 3.1.

Rujul Arora commented

2021-11-25 18:50:38 +01:00

In #93346#1259834, @Alaska wrote:

In #93346#1259781, @sharukh345 wrote:
Another interesting thing I've noticed, the issue only appears when the mesh is away from the centre of the world. When it's near the centre, the issue resolves by itself.

This indicates a precision issue. D12954: Removing ray offestting attempts to address issues like this. And testing that patch does indeed resolve the issue for me. The patch will probably be implemented into Blender 3.1.

Thanks! However, I really have no idea how to implement the patch by myself in the version of Blender I am using. Can you please tell me how to do that?

> In #93346#1259834, @Alaska wrote: >> In #93346#1259781, @sharukh345 wrote: >>Another interesting thing I've noticed, the issue only appears when the mesh is away from the centre of the world. When it's near the centre, the issue resolves by itself. > > This indicates a precision issue. [D12954: Removing ray offestting](https://archive.blender.org/developer/D12954) attempts to address issues like this. And testing that patch does indeed resolve the issue for me. The patch will probably be implemented into Blender 3.1. Thanks! However, I really have no idea how to implement the patch by myself in the version of Blender I am using. Can you please tell me how to do that?

Alaska commented

2021-11-25 22:32:40 +01:00

In #93346#1260136, @sharukh345 wrote:
Thanks! However, I really have no idea how to implement the patch by myself in the version of Blender I am using. Can you please tell me how to do that?

Applying the patch to your version of Blender means you need to compile Blender from the source code and as such requires some technical knowledge. If you wish to try this out, you can follow these two guides for building Blender and enabling CUDA/OptiX support in it:

Instructions for building Blender (You only need to focus on the "Quick Setup"): https://wiki.blender.org/wiki/Building_Blender/Windows
After you've got Blender working via this method, it's time to add CUDA and OptiX support by following this guide: https://wiki.blender.org/wiki/Building_Blender/CUDA

If you have any questions during the process, https://blender.chat/channel/blender-builds is probably the best place to ask for help.
Following building Blender, you will need to apply the patch to it. https://blender.chat/channel/blender-builds is also probably the best place to ask for help doing that.

> In #93346#1260136, @sharukh345 wrote: > Thanks! However, I really have no idea how to implement the patch by myself in the version of Blender I am using. Can you please tell me how to do that? Applying the patch to your version of Blender means you need to compile Blender from the source code and as such requires some technical knowledge. If you wish to try this out, you can follow these two guides for building Blender and enabling CUDA/OptiX support in it: > Instructions for building Blender (You only need to focus on the "Quick Setup"): https://wiki.blender.org/wiki/Building_Blender/Windows > After you've got Blender working via this method, it's time to add CUDA and OptiX support by following this guide: https://wiki.blender.org/wiki/Building_Blender/CUDA If you have any questions during the process, https://blender.chat/channel/blender-builds is probably the best place to ask for help. Following building Blender, you will need to apply the patch to it. https://blender.chat/channel/blender-builds is also probably the best place to ask for help doing that.

William Leeson commented

2021-11-30 14:35:13 +01:00

Added subscriber: @leesonw

William Leeson commented

2021-11-30 14:35:13 +01:00

I rendered this with the no ray offsetting patch D12954 also and it appears to work :-)

I am hoping to get this patch in soon.

I rendered this with the no ray offsetting patch [D12954](https://archive.blender.org/developer/D12954) also and it appears to work :-) ![BGRep_working.png](https://archive.blender.org/developer/F12668878/BGRep_working.png) I am hoping to get this patch in soon.

Rujul Arora commented

2021-12-03 17:54:47 +01:00

In #93346#1260189, @Alaska wrote:

In #93346#1260136, @sharukh345 wrote:
Thanks! However, I really have no idea how to implement the patch by myself in the version of Blender I am using. Can you please tell me how to do that?

Applying the patch to your version of Blender means you need to compile Blender from the source code and as such requires some technical knowledge. If you wish to try this out, you can follow these two guides for building Blender and enabling CUDA/OptiX support in it:

Instructions for building Blender (You only need to focus on the "Quick Setup"): https://wiki.blender.org/wiki/Building_Blender/Windows
After you've got Blender working via this method, it's time to add CUDA and OptiX support by following this guide: https://wiki.blender.org/wiki/Building_Blender/CUDA

If you have any questions during the process, https://blender.chat/channel/blender-builds is probably the best place to ask for help.
Following building Blender, you will need to apply the patch to it. https://blender.chat/channel/blender-builds is also probably the best place to ask for help doing that.

In #93346#1262341, @leesonw wrote:
I rendered this with the no ray offsetting patch D12954 also and it appears to work :-)

I am hoping to get this patch in soon.

Thanks so much, guys! I'll figure out how to implement the patch into Blender and share the results.

> In #93346#1260189, @Alaska wrote: >> In #93346#1260136, @sharukh345 wrote: >> Thanks! However, I really have no idea how to implement the patch by myself in the version of Blender I am using. Can you please tell me how to do that? > > Applying the patch to your version of Blender means you need to compile Blender from the source code and as such requires some technical knowledge. If you wish to try this out, you can follow these two guides for building Blender and enabling CUDA/OptiX support in it: > > >> Instructions for building Blender (You only need to focus on the "Quick Setup"): https://wiki.blender.org/wiki/Building_Blender/Windows >> After you've got Blender working via this method, it's time to add CUDA and OptiX support by following this guide: https://wiki.blender.org/wiki/Building_Blender/CUDA > > If you have any questions during the process, https://blender.chat/channel/blender-builds is probably the best place to ask for help. > Following building Blender, you will need to apply the patch to it. https://blender.chat/channel/blender-builds is also probably the best place to ask for help doing that. > In #93346#1262341, @leesonw wrote: > I rendered this with the no ray offsetting patch [D12954](https://archive.blender.org/developer/D12954) also and it appears to work :-) > > ![BGRep_working.png](https://archive.blender.org/developer/F12668878/BGRep_working.png) > > I am hoping to get this patch in soon. Thanks so much, guys! I'll figure out how to implement the patch into Blender and share the results.

Alaska commented

2021-12-14 21:09:28 +01:00

Closed as duplicate of #43835

Alaska closed this issue

2021-12-14 21:09:28 +01:00

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Artefacts appear when ambient occlusion (AO) is enabled #93346