Animation causes the face to be black

[fire]

@lyuma#781

Playing the A animation causes the face to be black.

eb5938a

Broken on both Windows and Linux.

Black.VRM.Model.Bug.mp4

[lyuma]

See here: this seems to be a Godot Engine bug.
godotengine/godot#10402

This bug happens in the sample project because there are two copies of the same Alicia vrm visible on-screen at the same time. Godot has a limitation that a mesh with blendshapes must only be rendered once per frame.

The workaround is to make the face mesh (every mesh with blend shapes) use "resource_local_to_scene = true". This has the consequence of wasting memory as each mesh will be duplicated, potentially along with all embedded materials and textures.

I will have to consider what to do with the the sample scene, considering that a user may encounter this bug and be confused. On the other hand, it is a good limitation to be aware of, and having the bug easily reproducible will teach the user what happens.

[fire]

I think the demo should show our best possible case in graphical quality.