- FBX "root bone" should become the Armature object itself, and not
an extra bone (follow same logic as Python importer did).
- "World to armature matrix" was not correct for armatures that are
parented under some other objects with transforms.
- Parenting imported meshes under an Armature was not taking into
account that the mesh bind transform might not be the same as the
current mesh node transform (i.e. was not setting "matrix parent
inverse" to compensate like the Python importer did).
- The repro file in #137768 also exposed an issue that importing custom
vertex normals was not working correctly in the new importer, when
mesh is partially invalid (validation alters the mesh, custom normals
have to be set afterwards).
Pull Request: https://projects.blender.org/blender/blender/pulls/138736
a96ecd2834