Multires: Spikes on base mesh verts when sculpting on lower levels #107095

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Julien Kaspar · 2023-04-18T17:57:43+02:00

Julien Kaspar commented

2023-04-18 17:57:43 +02:00

System Information
Operating system: Linux-6.2.11-gentoo-x86_64-AMD_Ryzen_Threadripper_1950X_16-Core_Processor-with-glibc2.36 64 Bits, X11 UI
Graphics card: Quadro GP100/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 530.41.03

Blender Version
Broken: version: 3.6.0 Alpha, branch: main, commit date: 2023-04-18 15:15, hash: 5bb3a3f1575d
Worked: (newest version of Blender that worked as expected)

Short description of error
This seems to be a recent regression.
When sculpting on any lower subdivision on a multires modifier, it causes spikes on base mesh vertices on the higher subdiv levels.

Exact steps for others to reproduce the error

Add any primitive object
Add a Multiresolution modifier and subdivide 5 times
Sculpt on level 1
See the result on the level 5

**System Information** Operating system: Linux-6.2.11-gentoo-x86_64-AMD_Ryzen_Threadripper_1950X_16-Core_Processor-with-glibc2.36 64 Bits, X11 UI Graphics card: Quadro GP100/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 530.41.03 **Blender Version** Broken: version: 3.6.0 Alpha, branch: main, commit date: 2023-04-18 15:15, hash: `5bb3a3f1575d` Worked: (newest version of Blender that worked as expected) **Short description of error** This seems to be a recent regression. When sculpting on any lower subdivision on a multires modifier, it causes spikes on base mesh vertices on the higher subdiv levels. **Exact steps for others to reproduce the error** - Add any primitive object - Add a Multiresolution modifier and subdivide 5 times - Sculpt on level 1 - See the result on the level 5

Screenshot_20230418_175528.png

441 KiB

Julien Kaspar added the

labels 2023-04-18 17:57:44 +02:00

Julien Kaspar commented

2023-04-18 18:32:47 +02:00

Another easy way to reproduce it actually is to start with any object and use the "Linear" subdivision button on the Multires modifier multiple times.

Stay_Here commented

2023-04-19 03:42:54 +02:00

Thank you so much for improving the Multires modifier! The Spikes seem a long standing issue, and people had been talking about it years ago, such as:
https://cgcookie.com/community/12027-fixed-hole-visible-in-multi-res-silly-bug
https://blenderartists.org/t/spike-appears-in-multires-and-getting-worse-everytime/1275173

Thank you so much for improving the Multires modifier! The Spikes seem a long standing issue, and people had been talking about it years ago, such as: https://cgcookie.com/community/12027-fixed-hole-visible-in-multi-res-silly-bug https://blenderartists.org/t/spike-appears-in-multires-and-getting-worse-everytime/1275173

~~Julien Kaspar referenced this issue 2023-04-19 10:10:01 +02:00~~

Multiresolution Issues #107118

Pratik Borhade commented

2023-04-19 13:32:57 +02:00

I can confirm.

This seems to be a recent regression.

Seems so. Particular case described in the report is introduced between 3.5-3.6
Will bisect

I can confirm. > This seems to be a recent regression. Seems so. Particular case described in the report is introduced between 3.5-3.6 Will bisect

Pratik Borhade added

Module

Sculpt, Paint & Texture

and removed

labels 2023-04-19 13:33:14 +02:00

Pratik Borhade commented

2023-04-19 14:31:45 +02:00

Git bisect points to: 16fbadde36
@HooglyBoogly ^

Git bisect points to: 16fbadde363c8074ec725fa1e1079add096bd741 @HooglyBoogly ^

Hans Goudey self-assigned this 2023-04-19 14:36:37 +02:00

Julien Kaspar added

and removed

labels 2023-04-24 14:48:06 +02:00

Hans Goudey commented

2023-04-25 03:50:27 +02:00

Small update: I've looked into this a few times, no luck yet. I'm going back in forth between reading the changes from 16fbadde36 looking for a mistake and investigating the existing code. It thought it might be related to some issues with creases, but that wasn't it. I found a few performance improvements to subdiv and multires in the meantime anyway.

Small update: I've looked into this a few times, no luck yet. I'm going back in forth between reading the changes from 16fbadde363c8074ec725fa1e1079add096bd741 looking for a mistake and investigating the existing code. It thought it might be related to some issues with creases, but that wasn't it. I found a few performance improvements to subdiv and multires in the meantime anyway.

🎉 1

Hans Goudey referenced this issue from a commit

2023-04-25 22:06:42 +02:00

Fix #107095: Spikes during multires reshape propagation

Hans Goudey closed this issue

2023-04-25 22:06:43 +02:00

Blender Bot added

and removed

labels 2023-04-25 22:06:44 +02:00

Stay_Here commented

2023-04-25 22:27:10 +02:00

@HooglyBoogly Congratulations! It seems that you have found the real cause. Although the fix may be simple, this is not an easy task. Thank you!

Hans Goudey commented

2023-04-26 01:27:02 +02:00

Thanks :)
In retrospect it's mostly about choosing the right bug fixing process-- this would have been simple from the start if I decided to selectively revert the more sketchy parts of the change.

Thanks :) In retrospect it's mostly about choosing the right bug fixing process-- this would have been simple from the start if I decided to selectively revert the more sketchy parts of the change.

👍 1

Germano Cavalcante referenced this issue

2023-05-08 20:09:03 +02:00

Sculpting with Multiresolution modifier makes object weird #107667

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