Skeleton doesn't deform mesh when imported as .blend, works fine with .glb

[sfreed141]

Godot version

4.0.3-stable_win64

System information

Windows 11, Blender 3.3

Issue description

In a couple .blend files I've noticed the built-in .blend importer results in broken mesh deformation. The skeleton shows up correctly but the mesh itself doesn't deform properly.

The animations work as expected in Blender, and if I export the mesh as a .glb (with all default settings) then importing that works as expected as well. It's definitely possible there's something wrong in the .blend file, but I'd still consider it a bug that the default-exported .glb behaves differently (at least my impression was that these two methods should behave identically).

Imported directly from .blend (skeleton doesn't deform mesh): (the bones only deforming some of the mesh objects in this wizard scene hints that maybe there's some trick to getting this to work. I tried messing with reparenting bones, checking weight paintings, and some other misc things but I couldn't figure it out :/)

Imported from .glb (skeleton deforms mesh):

(both models are from https://quaternius.com/, good stuff!)

Steps to reproduce

Open attached project and open the trex_*.tscn or wizard_*.tscn. Select the AnimationPlayer and see how the deformation works with the *_glb scenes but not the *_blend scenes. I included the .blend and .glb files as well.

Minimal reproduction project

import-issue.zip

[bitsawer]

Animations seem to work on current 4.1 master branch (68193bee9a1f77427a13b92508d611b1e2110217) on all four test scenes, so I guess something has been fixed at some point. However, there seems to be some geometry processing issue with the trex_blend.tscn. Looks like it might be LOD related, disabling or adjusting the LOD bias hides the issue. Or maybe the LOD just generates bad versions from a geometry that was wrong to begin with. There are some LOD generation bugs: https://github.com/godotengine/godot/issues/57416

.blend imports with strange geometry streching in the highlighted area:

LOD blowing up when adjusting the camera angle slightly:

[philipp-gaddi]

i got the same result as bitsawer, but the animations are working and deforming the mesh. i couldn't reproduce the error as sfreed141. setting in the importer tab skins to 4 influences (compatible). seems to solve this. so what is this option changing compared to all influences.

[sfreed141]

I can confirm @philipp-gaddi's suggestion to set Meshes > Skins to 4 Influences in the Import tab appears to solve the problem. Thanks!

I'd love to know what that 4 Influences does as well, since there's no in-editor tooltip and the official docs only describe non-.blend import settings (Importing Scenes docs). It'd be great to add docs for all the Import properties under the Blender group

And @bitsawer that's interesting, I just tried on 4.1-beta3 and I see the same behavior as 4.0.3 (no deforms). However the same trick of setting Meshes > Skins to 4 Influences appears to work. I don't see any of the strange geometry issues you noticed on 4.1-beta3 either (LOD related or otherwise).

edit: Just tried on latest master (030c1a950e) and I have the same behavior as 4.0.3 and 4.1-beta3. No strange geometry issues, have to set Meshes > Skins to 4 Influences to get deforms working properly. In case it matters my repro steps were

1. close project
2. delete the *.import files
3. open project
4. create new inherited scene (the pre-made inherited scenes exhibited the same behavior, but I remember when this used to be bugged and the inherited parts wouldn't update. Glad to see that part is fixed now!)

[fire]

Godot Engine supports 8 influences.

1. Blender export only supports 4 or all (infinity).

Not sure the best approach. I discussed with @julienduroure a few times over the years about this.

See also Vertex bone influence limits for 3D tools

[julienduroure]

A better option tuning is in todo list and should land in Blender 4.0 or 4.1

[dsyze]

I can confirm @philipp-gaddi's suggestion to set Meshes > Skins to 4 Influences in the Import tab appears to solve the problem. Thanks!

I'd love to know what that 4 Influences does as well, since there's no in-editor tooltip and the official docs only describe non-.blend import settings (Importing Scenes docs). It'd be great to add docs for all the Import properties under the Blender group

And @bitsawer that's interesting, I just tried on 4.1-beta3 and I see the same behavior as 4.0.3 (no deforms). However the same trick of setting Meshes > Skins to 4 Influences appears to work. I don't see any of the strange geometry issues you noticed on 4.1-beta3 either (LOD related or otherwise).

edit: Just tried on latest master (030c1a9) and I have the same behavior as 4.0.3 and 4.1-beta3. No strange geometry issues, have to set Meshes > Skins to 4 Influences to get deforms working properly. In case it matters my repro steps were

1. close project
2. delete the *.import files
3. open project
4. create new inherited scene (the pre-made inherited scenes exhibited the same behavior, but I remember when this used to be bugged and the inherited parts wouldn't update. Glad to see that part is fixed now!)

Thank you so much! That really worked!

[fire]

https://github.com/KhronosGroup/glTF-Blender-IO/pull/1983 Please help us review the Blender 4.0 feature to limit the MAX influences rather than picking either 4 or all.

Godot supports 4 or 8 bone vertex influence (blend weights).