Faces behaving as if normals are flipped #100338

New Issue

Geoffrey Blackwell · 2022-08-11T04:54:01+02:00

2022-08-11 04:54:01 +02:00

System Information
Operating system: Linux-5.18.10-76051810-generic-x86_64-with-glibc2.35 64 Bits
Graphics card: NVIDIA GeForce RTX 3070 Laptop GPU/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 470.129.06

Blender Version
Broken: version: 3.2.2, branch: master, commit date: 2022-08-02 18:15, hash: bcfdb14560
Worked: NA (also tested in current daily build and 3.4 alpha with same results)

Short description of error
After duplicating a set of faces and rotating them into place (the bulging window and surrounding frame marked by the 3D cursor in the attached blend file) the duplicated faces behave roughly as though their normals were flipped. There appear to be no overlapping vertices or faces

Exact steps for others to reproduce the error

Open the attached Structure.blend.
Turn on Auto Smooth. Although the mesh is set to Shade Flat, the shading of the problematic faces will change.
Set to Shade Smooth. The shading on the problematic faces will change drastically. In addition, the rest of the faces on the mesh will be shaded smooth regardless of whether Auto Smooth is toggled.

structure.blend

**System Information** Operating system: Linux-5.18.10-76051810-generic-x86_64-with-glibc2.35 64 Bits Graphics card: NVIDIA GeForce RTX 3070 Laptop GPU/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 470.129.06 **Blender Version** Broken: version: 3.2.2, branch: master, commit date: 2022-08-02 18:15, hash: `bcfdb14560` Worked: NA (also tested in current daily build and 3.4 alpha with same results) **Short description of error** After duplicating a set of faces and rotating them into place (the bulging window and surrounding frame marked by the 3D cursor in the attached blend file) the duplicated faces behave roughly as though their normals were flipped. There appear to be no overlapping vertices or faces **Exact steps for others to reproduce the error** 1) Open the attached Structure.blend. 2) Turn on Auto Smooth. Although the mesh is set to Shade Flat, the shading of the problematic faces will change. 3) Set to Shade Smooth. The shading on the problematic faces will change drastically. In addition, the rest of the faces on the mesh will be shaded smooth regardless of whether Auto Smooth is toggled. [structure.blend](https://archive.blender.org/developer/F13359865/structure.blend)

Geoffrey Blackwell commented

2022-08-11 04:54:01 +02:00

Added subscriber: @Geoffrey-T.Blackwell

Pratik Borhade commented

2022-08-11 06:41:20 +02:00

Added subscriber: @PratikPB2123

Pratik Borhade commented

2022-08-11 06:41:20 +02:00

Changed status from 'Needs Triage' to: 'Needs User Info'

Pratik Borhade commented

2022-08-11 06:41:20 +02:00

Thanks for the report. Clearing custom split normals solve the shading issue for me.
Did you perform any operation in edit mode or applied modifier to the mesh to improve shading?

Thanks for the report. Clearing custom split normals solve the shading issue for me. Did you perform any operation in edit mode or applied modifier to the mesh to improve shading?

Geoffrey Blackwell commented

2022-08-11 19:14:31 +02:00

Did you perform any operation in edit mode or applied modifier to the mesh to improve shading?

No, I didn't take any steps to do with shading beyond Set Smooth/Auto Smooth. Making the model involved cutting the bottom off a sphere, deleting a few faces, cutting the quads around the windows using the knife tool, and using grid fill for the windows.

I'm a lowly hobbyist and have absolutely no idea what "custom split normals" are. I'll need to do some googling.

> Did you perform any operation in edit mode or applied modifier to the mesh to improve shading? No, I didn't take any steps to do with shading beyond Set Smooth/Auto Smooth. Making the model involved cutting the bottom off a sphere, deleting a few faces, cutting the quads around the windows using the knife tool, and using grid fill for the windows. I'm a lowly hobbyist and have absolutely no idea what "custom split normals" are. I'll need to do some googling.

Geoffrey Blackwell commented

2022-08-13 00:09:15 +02:00

Clearing the custom split normals did fix the issue, though I still can't figure out how it happened in the first place.

Pratik Borhade commented

2022-08-16 07:44:38 +02:00

Changed status from 'Needs User Info' to: 'Needs Triage'

Omar Emara commented

2022-08-16 12:10:05 +02:00

Added subscriber: @OmarEmaraDev

Omar Emara commented

2022-08-16 12:10:05 +02:00

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

Omar Emara closed this issue

2022-08-16 12:10:05 +02:00

Omar Emara commented

2022-08-16 12:10:05 +02:00

Since the issue turned out to be just unexpected custom normals, I think we can archive this report.
If you are able to replicate the creation of custom normals again using defined steps where it is unexpected, feel free to state those steps and we can reopen and look into it then.

Since the issue turned out to be just unexpected custom normals, I think we can archive this report. If you are able to replicate the creation of custom normals again using defined steps where it is unexpected, feel free to state those steps and we can reopen and look into it then.

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Faces behaving as if normals are flipped #100338