Flat shading with alembic #96513

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opened 2022-03-16 09:38:22 +01:00 by Valentin Bonhomme · 12 comments

System Information
Operating system: Linux-5.4.0-104-generic-x86_64-with-glibc2.31 64 Bits
Graphics card: NVIDIA GeForce RTX 2080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 470.103.01

Blender Version
Broken: version: 3.1.0, branch: master, commit date: 2022-03-08 18:16, hash: c77597cd0e
Broken: version: 3.0.0
Broken: version: 2.9.0

Short description of error
Hello,
I tried to import a low poly alembic (containing several frames with several topologies). I tried to shade it flat (using right-click / Shade Flat) and it seemed to have no effect.

I tried with importing only a OBJ (one frame) and another alembic (containing this time only one frame). It works in both cases.
See below one frame alembic (left) and multi frames alembic (right) with Shade Flat :

Screenshot from 2022-03-16 09-12-12.png

I send you in attachments 2 alembic files : fire_256.abc (one frame) and fire_all.abc (several frames).

I found this report for long time ago, it looks connected : https://developer.blender.org/T69182

Thanks for your work !

Exact steps for others to reproduce the error
To reproduce it, import the 2 alembic files. Uncheck 'Vertex Interpolation' in MeshSequenceCache modifier.
Right click on them and Shade Flat.

fire_256.abc
fire_all.abc

**System Information** Operating system: Linux-5.4.0-104-generic-x86_64-with-glibc2.31 64 Bits Graphics card: NVIDIA GeForce RTX 2080 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 470.103.01 **Blender Version** Broken: version: 3.1.0, branch: master, commit date: 2022-03-08 18:16, hash: `c77597cd0e` Broken: version: 3.0.0 Broken: version: 2.9.0 **Short description of error** Hello, I tried to import a low poly alembic (containing several frames with several topologies). I tried to shade it flat (using right-click / Shade Flat) and it seemed to have no effect. I tried with importing only a OBJ (one frame) and another alembic (containing this time only one frame). It works in both cases. See below one frame alembic (left) and multi frames alembic (right) with Shade Flat : ![Screenshot from 2022-03-16 09-12-12.png](https://archive.blender.org/developer/F12929747/Screenshot_from_2022-03-16_09-12-12.png) I send you in attachments 2 alembic files : fire_256.abc (one frame) and fire_all.abc (several frames). I found this report for long time ago, it looks connected : https://developer.blender.org/T69182 Thanks for your work ! **Exact steps for others to reproduce the error** To reproduce it, import the 2 alembic files. Uncheck 'Vertex Interpolation' in MeshSequenceCache modifier. Right click on them and Shade Flat. [fire_256.abc](https://archive.blender.org/developer/F12929745/fire_256.abc) [fire_all.abc](https://archive.blender.org/developer/F12929746/fire_all.abc)

Added subscriber: @ValentinBonhomme

Added subscriber: @ValentinBonhomme
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Added subscriber: @PratikPB2123

Added subscriber: @PratikPB2123
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Changed status from 'Needs Triage' to: 'Needs User Info'

Changed status from 'Needs Triage' to: 'Needs User Info'
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Hi, thanks for the report.
When I deselect Faces from read data, faces appears as flat shaded but only for the first frame.

Is this what you are trying to explain in the report as a issue?

Hi, thanks for the report. When I deselect `Faces` from read data, faces appears as flat shaded but only for the first frame. Is this what you are trying to explain in the report as a issue?

Hi, thanks for considering my report.

To be honest, I didn't try to deselect Faces. Through my experience, deselect it create weird interpolation artifacts (due to topology changes). You can play the fire_all without Faces to see them.

My report was about using Face Normals (with Shade Flat) keeping default options. This works for 'fire_256.abc' (which have only one frame) but not for 'fire_alll.abc', neither for the first nor for any frame.

Solving the issue you are talking about, could be a part of the solution but will not solve totally my problem.

Hi, thanks for considering my report. To be honest, I didn't try to deselect Faces. Through my experience, deselect it create weird interpolation artifacts (due to topology changes). You can play the fire_all without Faces to see them. My report was about using Face Normals (with Shade Flat) keeping default options. This works for 'fire_256.abc' (which have only one frame) but not for 'fire_alll.abc', neither for the first nor for any frame. Solving the issue you are talking about, could be a part of the solution but will not solve totally my problem.
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Changed status from 'Needs User Info' to: 'Needs Developer To Reproduce'

Changed status from 'Needs User Info' to: 'Needs Developer To Reproduce'
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Added subscriber: @dr.sybren

Added subscriber: @dr.sybren
Member

Thanks for the information.
I can reproduce the issue as described.

Behavior is same on previous versions (2.83) and also my knowledge is weak in this area.
So I'm not really sure if this is a bug or a known issue.
@dr.sybren hi, can you check this report?

Thanks for the information. I can reproduce the issue as described. Behavior is same on previous versions (2.83) and also my knowledge is weak in this area. So I'm not really sure if this is a bug or a known issue. @dr.sybren hi, can you check this report?

Added subscriber: @SteffenD

Added subscriber: @SteffenD

Added subscriber: @EvertonSchneider

Added subscriber: @EvertonSchneider

Hi, I tried to shade flat through Geometry nodes and it worked.
I think that somehow the smooth shading (Phong angle in other software) is stored in the .abc and can't be overridden via operator, but geometry nodes do.

Screenshot from 2022-03-16 14-32-00.png

Hi, I tried to shade flat through Geometry nodes and it worked. I think that somehow the smooth shading (Phong angle in other software) is stored in the .abc and can't be overridden via operator, but geometry nodes do. ![Screenshot from 2022-03-16 14-32-00.png](https://archive.blender.org/developer/F12930427/Screenshot_from_2022-03-16_14-32-00.png)

Hi, thanks for your answers.
I'm glad there is a way to do what I wanted to do !

Would it be possible to create a more straight forward solution ?
Other people could have the same issue and not sure they think to use Geometry Node...

Hi, thanks for your answers. I'm glad there is a way to do what I wanted to do ! Would it be possible to create a more straight forward solution ? Other people could have the same issue and not sure they think to use Geometry Node...
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Reference: blender/blender#96513
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