Custom Split Normals can look bad after posing mesh (Stretching areas) #114529

New Issue

刘文博 · 2023-11-06T11:33:04+01:00

刘文博 commented

2023-11-06 11:33:04 +01:00

System Information
Operating system: Windows-10-10.0.22621-SP0 64 Bits
Graphics card: NVIDIA GeForce RTX 3070 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 531.79

Blender Version
Broken: version: 3.6.5, branch: blender-v3.6-release, commit date: 2023-10-16 14:30, hash: cf1e1ed46b7e
Worked: (newest version of Blender that worked as expected)

Short description of error
Calculation error of normals at the point of mesh stretching when the mesh has custom split normals data
The normals are no longer smooth.Other softwares like ue,3dmax don't seem to have this problem.The normals are smooth.

Blender:	UE:	3D Max:

Exact steps for others to reproduce the error
1 Import test.fbx
2 Lift the arm

**System Information** Operating system: Windows-10-10.0.22621-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 3070 Ti/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 531.79 **Blender Version** Broken: version: 3.6.5, branch: blender-v3.6-release, commit date: 2023-10-16 14:30, hash: `cf1e1ed46b7e` Worked: (newest version of Blender that worked as expected) **Short description of error** Calculation error of normals at the point of mesh stretching when the mesh has custom split normals data The normals are no longer smooth.Other softwares like ue,3dmax don't seem to have this problem.The normals are smooth. | Blender: | UE: | 3D Max: | | -- | -- | -- | |![image](/attachments/8582d104-286b-45a0-a39b-32566bae720e)|![image](/attachments/2f9f8e24-14f8-4c54-9ea2-097169fcb366)|![image](/attachments/03155597-bda3-4238-9b1b-0396270c793f) **Exact steps for others to reproduce the error** 1 Import test.fbx 2 Lift the arm

image.png

4.5 MiB

test.fbx

1.3 MiB

image.png

1.4 MiB

image.png

1.9 MiB

刘文博 added the

labels 2023-11-06 11:33:05 +01:00

Germano Cavalcante commented

2023-11-06 17:14:49 +01:00

I can confirm.
But at first glance it appears to be a problem with the mesh itself.
I'm not familiar with UE or 3D Max to check how normal customs are transformed there.
I'll leave it to someone with more knowledge in this area to investigate.

I can confirm. But at first glance it appears to be a problem with the mesh itself. I'm not familiar with UE or 3D Max to check how normal customs are transformed there. I'll leave it to someone with more knowledge in this area to investigate.

custom_normal_test.blend

2.3 MiB

刘文博 commented

2023-11-07 03:36:19 +01:00

I can confirm.
But at first glance it appears to be a problem with the mesh itself.
I'm not familiar with UE or 3D Max to check how normal customs are transformed there.
I'll leave it to someone with more knowledge in this area to investigate.

@mano-wii
I exported an FBX from 3ds max and imported it into Blender.The new file does not have this issue.I think blender's algorithm caused this problem.

> I can confirm. > But at first glance it appears to be a problem with the mesh itself. > I'm not familiar with UE or 3D Max to check how normal customs are transformed there. > I'll leave it to someone with more knowledge in this area to investigate. @mano-wii I exported an FBX from 3ds max and imported it into Blender.The new file does not have this issue.I think blender's algorithm caused this problem. ![image](/attachments/63ead997-a43f-4de1-acd6-34900231496b)

image.png

1.6 MiB

test.blend

1.6 MiB

刘文博 commented

2023-11-07 03:55:07 +01:00

I can confirm.
But at first glance it appears to be a problem with the mesh itself.
I'm not familiar with UE or 3D Max to check how normal customs are transformed there.
I'll leave it to someone with more knowledge in this area to investigate.

I don't think turning off Auto Smooth is a good solution.This will render the custom split normals data ineffective.

> I can confirm. > But at first glance it appears to be a problem with the mesh itself. > I'm not familiar with UE or 3D Max to check how normal customs are transformed there. > I'll leave it to someone with more knowledge in this area to investigate. I don't think turning off Auto Smooth is a good solution.This will render the custom split normals data ineffective.

Germano Cavalcante commented

2023-11-07 12:01:00 +01:00

Thanks for testing @iillya,

From the image we can see that the mesh imported from 3d max also has custom normals, but the normals seem to be better aligned than the one imported directly into Blender through FBX.

But you seem to have already imported the posed mesh. (So it could also be a rigging problem).

Could it be a precision problem with Blender's FBX importer?
Could it be that 3D Max somehow made the normals more aligned?
Could it be that 3D Max and UE rigging handle this case better than Blender?

@Mysteryem, since you seem more familiar with this area, any ideas on how to solve the mystery of what might be going on here?

Thanks for testing @iillya, From the image we can see that the mesh imported from 3d max also has custom normals, but the normals seem to be better aligned than the one imported directly into Blender through FBX. But you seem to have already imported the posed mesh. (So it could also be a rigging problem). Could it be a precision problem with Blender's FBX importer? Could it be that 3D Max somehow made the normals more aligned? Could it be that 3D Max and UE rigging handle this case better than Blender? @Mysteryem, since you seem more familiar with this area, any ideas on how to solve the mystery of what might be going on here?

Thomas Barlow commented

2023-11-07 14:17:46 +01:00

I think this may be a case of Blender rigging not handling custom normals as well as other software. The FBX importer simply imports whatever normals are in the .fbx directly as custom split normals (expanding the normals to the 'CORNER' domain if they were face or vertex normals, though they're already 'CORNER' domain in test.fbx).

If I pose the imported .fbx and transfer custom normals to it from the pre-posed 3ds import it looks good initially, but then un-posing the imported .fbx results in the normals on the shoulder no longer looking good.

Unity similarly looks good when posed (both the original test.fbx and an .fbx exported from test.blend):

I think this may be a case of Blender rigging not handling custom normals as well as other software. The FBX importer simply imports whatever normals are in the .fbx directly as custom split normals (expanding the normals to the 'CORNER' domain if they were face or vertex normals, though they're already 'CORNER' domain in `test.fbx`). If I pose the imported .fbx and transfer custom normals to it from the pre-posed 3ds import it looks good initially, but then un-posing the imported .fbx results in the normals on the shoulder no longer looking good. ![image](/attachments/fe30dcb5-1d68-40b1-ae63-3d64241d5eee) Unity similarly looks good when posed (both the original `test.fbx` and an .fbx exported from `test.blend`): ![image](/attachments/4c1323c8-6cf2-44bb-8990-d6cdc8fc664e)

image.png

781 KiB

image.png

267 KiB

刘文博 commented

2023-11-07 14:25:25 +01:00

Thanks for testing @iillya,

From the image we can see that the mesh imported from 3d max also has custom normals, but the normals seem to be better aligned than the one imported directly into Blender through FBX.

But you seem to have already imported the posed mesh. (So it could also be a rigging problem).

Could it be a precision problem with Blender's FBX importer?
Could it be that 3D Max somehow made the normals more aligned?
Could it be that 3D Max and UE rigging handle this case better than Blender?

@Mysteryem, since you seem more familiar with this area, any ideas on how to solve the mystery of what might be going on here?

Yes I have already imported the posed mesh.(The one on the right，posed in max instead of in blender).What I want to show is that just like you said ，3D Max and UE rigging handle this case better than Blender.Nothing to do with blender's FBX importer.May be related to rigging.

> Thanks for testing @iillya, > > From the image we can see that the mesh imported from 3d max also has custom normals, but the normals seem to be better aligned than the one imported directly into Blender through FBX. > > But you seem to have already imported the posed mesh. (So it could also be a rigging problem). > > Could it be a precision problem with Blender's FBX importer? > Could it be that 3D Max somehow made the normals more aligned? > Could it be that 3D Max and UE rigging handle this case better than Blender? > > @Mysteryem, since you seem more familiar with this area, any ideas on how to solve the mystery of what might be going on here? Yes I have already imported the posed mesh.(The one on the right，posed in max instead of in blender).What I want to show is that just like you said ，3D Max and UE rigging handle this case better than Blender.Nothing to do with blender's FBX importer.May be related to rigging.

刘文博 commented

2023-11-07 14:38:13 +01:00

@Mysteryem
So this is a problem with blender's own rigging. Is it not as perfect as other software?Are there any plans to fix this issue in the future?

@Mysteryem So this is a problem with blender's own rigging. Is it not as perfect as other software?Are there any plans to fix this issue in the future?

Germano Cavalcante changed title from ~~Calculation error of normals at the point of mesh stretching when the mesh has custom split normals data~~ to Custom Split Normals can look bad after posing mesh (Stretching areas)

2023-11-07 21:47:20 +01:00

Germano Cavalcante added

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Custom Split Normals can look bad after posing mesh (Stretching areas) #114529