How to export VoxelLodTerrain or VoxelTerrain as glb, at runtime ?

[filemon-filemon]

I use godot 4.5.1.stable, and am trying to export as glb the generated terrain at runtime.
When I use the method described in the documentation on a mesh, it works just fine, and when I use it on the VoxelLodTerrain, it prints a bugged glb file that seems empty.

My code is

func _input(_event: InputEvent) -> void:
	if Input.is_action_just_pressed("export"):
		var gltf_document_save := GLTFDocument.new()
		var gltf_state_save := GLTFState.new()
		gltf_document_save.append_from_scene($VoxelLodTerrain, gltf_state_save)
		gltf_document_save.write_to_filesystem(gltf_state_save, "user://test.glb")

Thank you so much !!

[Zylann]

In a lot of features like this gathering the scene tree, Godot assumes everything is using MeshInstance3D nodes. But that ignores all custom nodes and plugins making use of RenderingServer under the hood. VoxelLodTerrain is one of these. It doesn't use nodes, it calls into RenderingServer directly. So using GLTFDocument.append_from_scene on it will not work. There doesn't seem to be any API in Godot to somehow register custom nodes so that they properly append themselves to such GLTFDocument out of the box.

So you would have to use a workaround that creates a copy of the entire terrain as a bunch of temporary MeshInstance3D nodes just so that function works, and then free them afterwards. But there is no such function at the moment. The closest is debug_dump_as_scene, but that is a debugging function so it doesn't necessarily converts what you expect.

Another way could also be to have a function of the terrain that directly writes stuff into a GLTFDocument, which could be preferable for lower overhead, but I am less knowledgable in that area.

There are also some caveats:

• VoxelLodTerrain adjusts level of details based on viewer location, so if you were to save a terrain as a GLTF document it will be detailed around the viewer's location but will have less and less details further away.
• If you use a ShaderMaterial, as is required for smooth voxels to render properly, those won't carry over because GLTF doesn't support it.

[filemon-filemon]

Thank you so much for your quick answer !!
That's such a shame :[
And what does the debug_dump_as_scene() function does exactly ?
I mean as its writer do you know how I might use it to export a gltf from it ?
There is no description for it in the doc and I'm unsure how to use it :O
Thanks again for your time !!!
And thanks so much for making and maintaining this plugin !!!!

[Zylann]

And what does the debug_dump_as_scene() function does exactly ?

Creates mesh instances representing the terrain, more or less. But it was made for debugging purposes so it might not work exactly like you want. Also, it creates a scene file, which is not what you'd need for appending to GLTF.

I mean as its writer do you know how I might use it to export a gltf from it ?

In editor, you could use it and then open the scene file it created in the editor and save that to GLTF, but again it might not contain what you want.

I can implement a function with a few more options which would create a bunch of mesh instances and return a Node3D that you can give to append_from_scene, but that will take some time.

[Zylann]

I added VoxelNode.convert_to_nodes in 10ecc34