Errors exporting udim textures

[3DE-Damien]

Describe the bug

• When I export an object with jpeg udim textures, the exporter crashes.
• UVs sharing vertex on UDIM limits are not correctly exported.
• Geometry using only one UDIM tile (other than 1001) are exported with the 1001 texture tile.

To Reproduce

• download and unzip Blender_gltf_udims.zip
• open gltf_udims.blend
• try exporting the scene or individual cubes

Expected behavior Getting results similar to Blender viewport

Screenshots

System Information Operating system: Windows-10-10.0.19045-SP0 64 Bits Graphics card: NVIDIA GeForce RTX 3060/PCIe/SSE2 NVIDIA Corporation 4.6.0 NVIDIA 565.90

Blender Version Broken: version: 4.2.3 LTS, branch: blender-v4.2-release, commit date: 2024-10-14 15:20, hash: 0e22e4fcea03 Worked: (newest version of Blender that worked as expected)

[julienduroure]

Let's go step by step.

Confirmed the crash. Root cause is a bad check of jpg/png file format on udim texture

[julienduroure]

Point 1 and 3 are fixed in #2384

The second one is much more complicated to manage, as

• There is some float precision issue
• We need to check, on limit, where should the point goes, (based on edges and faces?) For this part of the bug report, no short term solution will probably happen.

[3DE-Damien]

Thank you Julien. I can accomodate the second point, I guess.

I would choose the right texture based on face center UVs location. There would be some issues with overflowing faces, but it's not supposed to happen with udims, AFAIK.