Retain meta data set on importer nodes

[tamask]

During the import process, ImporterMeshInstance3D nodes are replaced with MeshInstance3D nodes. This change copies over any meta data that might have been set during the import process, for example, in a GLTFDocumentExtension.

This is a resolution for godotengine/godot-proposals#6586.

[tamask]

I've updated this pull request to be more thorough with copying over meta data on various imported nodes, not just ImporterMeshInstance3D.

[tamask]

I've updated the pull request to also copy over metadata from ImporterMesh to ArrayMesh. In addition to ImporterMeshInstance3D, ImporterMesh is the other intermediary class used where metadata set in a GLTFDocumentExtension would be lost.

Here's an example use case in a GLTFDocumentExtension that copies over the extras from the gltf json so that it's available in the packed scene in godot:

func _apply_extras_to_meshes(state: GLTFState) -> void:
    for index: int in range(state.meshes.size()):
        var extras: Dictionary = state.json.meshes[index].get("extras", {})
        var mesh: GLTFMesh = state.meshes[index]
        _apply_extras_to_meta(state, mesh.mesh, extras)

This way, custom properties set in blender on the mesh data can be conveyed over to the godot side via gltf.

[lyuma]

Looks good and easily digestible so I think it should be safe in 4.3 - Would it be possible to implement the same change in modules/gltf/extensions/gltf_document_extension_convert_importer_mesh.cpp ?
Basically, the GLTFDocumentExtension is the corresponding process for runtime GLTFDocument import, since the editor import pipeline code is not enabled at runtime.

https://github.com/godotengine/godot/blob/master/modules/gltf/extensions/gltf_document_extension_convert_importer_mesh.cpp
It's only in one place, so duplicating the contents of _copy_meta is acceptable in this case.

[tamask]

Looks good and easily digestible so I think it should be safe in 4.3 - Would it be possible to implement the same change in modules/gltf/extensions/gltf_document_extension_convert_importer_mesh.cpp ? Basically, the GLTFDocumentExtension is the corresponding process for runtime GLTFDocument import, since the editor import pipeline code is not enabled at runtime.

https://github.com/godotengine/godot/blob/master/modules/gltf/extensions/gltf_document_extension_convert_importer_mesh.cpp It's only in one place, so duplicating the contents of _copy_meta is acceptable in this case.

Absolutely, I've updated the pull request source branch to reflect this.

[lyuma]

This will fix a source of confusion when working with import plugins. Great work!

[akien-mga]

Thanks! And congrats for your first merged Godot contribution 🎉

[tamask]

Thanks! And congrats for your first merged Godot contribution 🎉

Wonderful, and thank you!