Custom split normal data on negative or non-uniform scaled geometries gets broken upon applying scale #121831

New Issue

Martin-Lorentzon · 2024-05-15T16:50:43+02:00

Martin-Lorentzon commented

2024-05-15 16:50:43 +02:00

System Information
Operating system: Windows-10-10.0.19045-SP0 64 Bits
Graphics card: Quadro RTX 5000 with Max-Q Design/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 516.69

Blender Version
Broken version: 4.2.0 Alpha, branch: main, commit date: 2024-05-15 08:16, hash: ed2be4c89f59
Broken version: 4.1.0
Broken version: 4.0
Broken version: 3.6.10 & 3.6 LTS
Broken version: 3.3LTS

Short description of error
Custom split normal data on negative or non-uniform scaled geometries gets broken upon applying scale.
This alone makes Blender difficult to work with when smooth decimated surfaces for optimized graphics are a requirement and they happen to come in as mirrored along one or multiple axes.

Exact steps for others to reproduce the error
Select Suzanne > Ctrl + A > (Apply) Scale

**System Information** Operating system: Windows-10-10.0.19045-SP0 64 Bits Graphics card: Quadro RTX 5000 with Max-Q Design/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 516.69 **Blender Version** Broken version: 4.2.0 Alpha, branch: main, commit date: 2024-05-15 08:16, hash: `ed2be4c89f59` Broken version: 4.1.0 Broken version: 4.0 Broken version: 3.6.10 & 3.6 LTS Broken version: 3.3LTS **Short description of error** Custom split normal data on negative or non-uniform scaled geometries gets broken upon applying scale. This alone makes Blender difficult to work with when smooth decimated surfaces for optimized graphics are a requirement and they happen to come in as mirrored along one or multiple axes. **Exact steps for others to reproduce the error** Select Suzanne > Ctrl + A > (Apply) Scale

suzanne_custom_split_normals_mirrored.blend

1.1 MiB

suzanne_custom_split_normals_mirrored_0.png

250 KiB

suzanne_custom_split_normals_mirrored_1.png

302 KiB

👍 1

Martin-Lorentzon added the

labels 2024-05-15 16:50:44 +02:00

YimingWu commented

2024-05-16 03:28:16 +02:00

Can confirm. I also had this problem when importing models, thought it's just some broken normals. Looks like it's a bug with applying transform 🤔

Does not happen in 4.0 apparently (and when importing other model + scaling works as well). Will raise priority

Can confirm. I also had this problem when importing models, thought it's just some broken normals. Looks like it's a bug with applying transform 🤔 Does not happen in 4.0 apparently (and when importing other model + scaling works as well). Will raise priority

YimingWu added

and removed

labels 2024-05-16 03:28:36 +02:00

YimingWu added

and removed

labels 2024-05-16 03:31:22 +02:00

Philipp Oeser commented

2024-05-16 08:57:20 +02:00

Does not happen in 4.0 apparently (and when importing other model + scaling works as well). Will raise priority

This is also broken in 4.0, 3.6LTS, 3.3LTS for me.
@ChengduLittleA : did you enable Normals > Auto Smooth in those versions?

Will lower the prio for now...

> Does not happen in 4.0 apparently (and when importing other model + scaling works as well). Will raise priority This is also broken in 4.0, 3.6LTS, 3.3LTS for me. @ChengduLittleA : did you enable `Normals` > `Auto Smooth` in those versions? Will lower the prio for now...

Philipp Oeser added

and removed

labels 2024-05-16 08:57:40 +02:00

YimingWu commented

2024-05-16 08:59:18 +02:00

@lichtwerk Well I did not specifically turn that option on 🤔, if it does then it's from the importer

Philipp Oeser commented

2024-05-16 09:05:32 +02:00

NOTE: could be that something like 93c8955a72 helps here (applying scale is not really a topo operation though...), or just something corresponding to multiresModifier_scale_disp ?

NOTE: could be that something like 93c8955a722b helps here (applying scale is not really a topo operation though...), or just something corresponding to `multiresModifier_scale_disp` ?

Philipp Oeser commented

2024-05-16 09:07:12 +02:00

@lichtwerk Well I did not specifically turn that option on 🤔, if it does then it's from the importer

If the option is not ON in older versions, you are not looking at custom normals ;) (they are only used with that option ON)

> @lichtwerk Well I did not specifically turn that option on 🤔, if it does then it's from the importer If the option is not ON in older versions, you are not looking at custom normals ;) (they are only used with that option ON)

Philipp Oeser commented

2024-05-16 10:11:54 +02:00

Also fails with positive, but non-uniform scaling (assume just anything where CornerNormalSpaceArray also changes?)

@HooglyBoogly might be interested?

Also fails with positive, but non-uniform scaling (assume just anything where `CornerNormalSpaceArray` also changes?) @HooglyBoogly might be interested?

Philipp Oeser changed title from ~~Custom split normal data on mirrored(negative scale) geometries gets broken upon applying scale~~ to Custom split normal data on negative or non-uniform scaled geometries gets broken upon applying scale

2024-05-16 10:12:40 +02:00

Martin-Lorentzon commented

2024-05-16 11:02:36 +02:00

Updated the issue with finds higher up. I can also confirm that it's broken in b4.0, just forgot to add it to the original post.

👍 1

Martin-Lorentzon commented

2024-05-16 13:46:07 +02:00

I found this thread which handles one specific case of the issue.
If anyone wants to join me in trying to generalize and update it for b4.1 (and b4.2 LTS) (with the updated mesh API) it would be very much appreciated.
This is of course not the ideal solution but would certainly help in dealing with the issue.

I found this [thread](https://blender.stackexchange.com/questions/212632/apply-1-x-scale-mirror-to-object-mesh-and-keep-custom-normals-with-python) which handles one specific case of the issue. If anyone wants to join me in trying to generalize and update it for b4.1 (and b4.2 LTS) (with the updated mesh API) it would be very much appreciated. This is of course not the _ideal_ solution but would certainly help in dealing with the issue.

Martin-Lorentzon commented

2024-05-16 13:55:46 +02:00

I managed to get something that may work(?)
It could be cleaned up but feel free to point out any mistakes

Edit:
There are a couple mistakes, I will work on correcting the code

Edit 2:
Slightly corrected code (Missing if statement for flipping faces fixed):

Edit 3:
Made a cleaned up version, and included a few comments...
I'm not sure I can further improve it on my own - it solves the issue for negative scaled meshes but not all non-uniform ones.
Would also be nice if it handled child objects similarly to the native Apply Scale...
https://pastebin.com/KrPJ7z2A

I managed to get something that may work(?) It could be cleaned up but feel free to point out any mistakes Edit: There are a couple mistakes, I will work on correcting the code Edit 2: Slightly corrected code (Missing if statement for flipping faces fixed): Edit 3: Made a cleaned up version, and included a few comments... I'm not sure I can further improve it on my own - it solves the issue for negative scaled meshes but not all non-uniform ones. Would also be nice if it handled child objects similarly to the native Apply Scale... https://pastebin.com/KrPJ7z2A

Robert Shea commented

2024-05-16 16:54:49 +02:00

Hello, thanks for the bug report, and investigation!

I would like to add, that this error occurs when joining objects, where one object has custom split normals and a negative scale (I did not check non uniform scales and joining objects).

Blender Version
Broken version: 4.0

Exact steps for others to reproduce the error
Select Mirrored Suzanne > Shift + select non mirrored Suzanne (So that non mirrored Suzanne is active) > Ctrl + J

It also works in the opposite selection order, breaking the normals on the non mirrored version, so the active selection always seems to keep it's split normals on joining.

(These meshes have all triangles (faces) un-welded, but it still occurs when all vertices are merged by distance, but much less noticeable)

Hello, thanks for the bug report, and investigation! I would like to add, that this error occurs when joining objects, where one object has custom split normals and a negative scale (I did not check non uniform scales and joining objects). Blender Version Broken version: 4.0 Exact steps for others to reproduce the error Select Mirrored Suzanne > Shift + select non mirrored Suzanne (So that non mirrored Suzanne is active) > Ctrl + J It also works in the opposite selection order, breaking the normals on the non mirrored version, so the active selection always seems to keep it's split normals on joining. (These meshes have all triangles (faces) un-welded, but it still occurs when all vertices are merged by distance, but much less noticeable)

join_objects_custom_normals.blend

1.5 MiB

👍 1

Sign in to join this conversation.

No Label

Download

What's New

Blender Studio

Manual

Developers Blog

Documentation

Benchmark

Blender Conference

Development Fund

One-time Donations

Custom split normal data on negative or non-uniform scaled geometries gets broken upon applying scale #121831