Projects upgraded from Godot 4.1 import existing FBX files with ufbx

[lyuma]

Tested versions

• Reproducible in 4.3dev6 / bd2300d

System information

Godot v4.3.beta (bd2300d) - Windows 10.0.19045 - Vulkan (Forward+) - dedicated NVIDIA GeForce RTX 3090 (NVIDIA; 31.0.15.3713) - Intel(R) Core(TM) i9-9900K CPU @ 3.60GHz (16 Threads)

Issue description

ufbx and FBX2glTF contain several subtle differences which can break compatibility of scene inheritance / NodePaths when switching a scene from one to the other.

We have an "Importer" dropdown in the import dock, but it defaults to ufbx even for projects migrated from older versions of Godot.

Example project.godot:

config_version=5

[application]

config/name="AnimsTest"
run/main_scene="res://main.tscn"
config/features=PackedStringArray("4.1", "Forward Plus")
config/icon="res://icon.svg"

[remap]

importer="animation_library"
importer_version=1
type="AnimationLibrary"
uid="uid://2m8uxc0jjmqh"
path="res://.godot/imported/SpearAtk_1.FBX-523bf0676781974a7233c3f61daa2882.res"

[deps]

source_file="res://SpearAtk_1.FBX"
dest_files=["res://.godot/imported/SpearAtk_1.FBX-523bf0676781974a7233c3f61daa2882.res"]

[params]

nodes/root_type="Node3D"
nodes/root_name="Scene Root"
nodes/apply_root_scale=true
nodes/root_scale=1.0
meshes/ensure_tangents=true
meshes/generate_lods=true
meshes/create_shadow_meshes=true
meshes/light_baking=1
meshes/lightmap_texel_size=0.2
skins/use_named_skins=true
animation/import=true
animation/fps=30
animation/trimming=false
animation/remove_immutable_tracks=true
import_script/path=""
_subresources={}
gltf/embedded_image_handling=1

On a migrated project, it will have fbx/importer=1 if using FBX2glTF and fbx/importer=0 for ufbx. If fbx/importer is missing, we should treat as FBX2glTF, I think.

Steps to reproduce

1. Open the attached project in a 4.3 build.
2. Click a .FBX file.
3. it will show importer = ufbx even though the project was created before ufbx was implemented.
4. Hierarchy will be missing RootNode which will break NodePath references.

Minimal reproduction project (MRP)

https://github.com/godotengine/godot/files/12619311/AnimsTest.zip

[lyuma]

Fixed by #92197