Vulkan: Triangle glitch on a model with a rectangle hole due to automatic mesh LOD

[Acvarium]

Godot version

v4.0.alpha2.official [79077e6]

System information

Ubuntu 21.10. nVidia GeForce GTX 870M with 470.103.01 driver. Vulkan

Issue description

A strange glitch, that I noticed on this model. Tested in blender, Godot 3.4.3 and F3D viewer. Does not show up in any of those, other then Godot 4.0 alpha 2 with bout Vulkan and Vulkan mobile render

Steps to reproduce

Open minimal reproduction project or import model

Minimal reproduction project

triangle_glitch.zip

[Calinou]

I can confirm this on master 1710211.

The triangle is only visible at certain viewing angles:

triangle_bug.mp4

Selecting the glb file in the FileSystem dock, going to the Import dock, disabling Generate Lods, clicking Reimport then reloading the saved scene fixes this issue. Therefore, this is caused by automatic mesh LOD.

[fire]

I think this is an upstream bug, might be easily fixable.

Confirmed.

Upstream is https://github.com/zeux/meshoptimizer

[fire]

May be fixed by #70446

[fire]

I think this is fixed by #70446. Like in the latest rc3.

[akien-mga]

Still reproducible in 4.0 RC 3:

[fire]

Maybe fixed now I can't find the angle that fails.

[zeux]

Yeah I can't reproduce it after reimport on master. I think this was fixed by #84384 - that version has an improvement to flip detection that would have solved cases like the above. Can probably close this.

[akien-mga]

Thanks for testing!

Fixed by #84384.