Bug 2212099

Summary: Blender subdivision is unusable
Product: [Fedora] Fedora Reporter: Matthew Woehlke <mwoehlke.floss>
Component: blenderAssignee: Luya Tshimbalanga <luya_tfz>
Status: CLOSED WORKSFORME QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 38CC: code, design-devel, epel-packagers-sig, kwizart, luya_tfz, negativo17
Target Milestone: ---   
Target Release: ---   
Hardware: x86_64   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2023-06-05 04:36:15 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Attachments:
Description Flags
Screenshot show how subvidision works none

Description Matthew Woehlke 2023-06-03 21:02:57 UTC 
Description of problem:
The subdivision modifier creates extremely broken meshes. Vertices appear to be placed randomly and probably some at infinity.

Version-Release number of selected component (if applicable):
blender-3.5.1-3.fc38.x86_64

How reproducible:
Always?

Steps to Reproduce:
1. Create a new, default document (or create any mesh).
2. Apply subdivision modifier.

Actual results:
The mesh either disappears or produces something that is clearly utter garbage. (If faces are visible at all, they look like noise and are completely black.)

Expected results:
Subdivision works as in 3.3 and 3.4.

Additional info:
blender-1:3.4.1-16.fc38.x86_64 does not seem to be affected.
Comment 1 Luya Tshimbalanga 2023-06-04 17:14:39 UTC 
Would you provide a screenshot to see the issue? I failed to reproduce the problem witht eh current version of Blender on AMD Ryzen 7 5825U.
Comment 2 Luya Tshimbalanga 2023-06-04 17:15:55 UTC 
Created attachment 1968849 [details]
Screenshot show how subvidision works
Comment 3 Matthew Woehlke 2023-06-05 04:36:15 UTC 
That's... interesting. It seems to be behaving itself now.

I've rebooted, but it was doing it from a relatively fresh boot previously.

I'm going to chalk it up to either:
- A *VERY* strange fluke.
- The previous installation was corrupt, somehow.
- Somehow caused by having run 3.3.fc36 previously followed by 3.5.fc38, and somehow fixed after running 3.4.fc38?

I'd been using a somewhat-old version of the fc36 package for some time (circa August 2022 at a guess). A few days ago, Blender wedged my machine (thank you Intel GPU drivers), which I used as an excuse to upgrade to fc38. I installed the latest fc36 version (while the older version was running, I think). I don't recall if I launched the latest fc36 version. I then did a distro-upgrade. After my first boot into fc38, it was broken. I subsequently downgraded to 3.4.fc38, which worked. After upgrading back to 3.5.1-3.fc38, it seems okay. I have no clue if something peculiar to that chain of actions caused it, or what.

As a professional software developer that's sometimes worked with 3D code, I'm confident what I saw was completely bogus and often non-finite vertex positions being generated, probably with invalid normals (i.e. values not in [-1, +1]) as well (explaining why, when I could see *anything*, it was solid black). What would cause *that specifically* (i.e. subdivision) to go haywire without Blender just plain crashing, I have not a clue. Very, very strange.

I guess I'll close this; if it happens again, I'll re-open with a screen shot. Meanwhile, this will be 'on file' in case anyone else runs into the same issue.