State of Interoperability between Godot and Blender

[aaronfranke]

@SimonThommes

Our focus here will be setting up a pipeline that accommodates a Blender centric workflow for all of the asset and level authoring and would ideally provide a seamless experience for working with Blender and Godot together.

The idea of this post is to collect the feedback and discussion points coming out of the project and opening up the conversation to others, especially also the Godot development community.

Hello Simon Thommes! My name is Aaron Franke. I am one of the main maintainers of the glTF import and export pipeline in Godot Engine. I would love to get involved in this project, and to get you and other Blender folks involved in the existing channels I’ve been using to discuss developing the asset pipeline. We at Godot, GD3D, and OMI have been working on the Godot and glTF side of the asset pipeline for awhile and we want to collaborate.

I saw in this Blender Studio Log 10 video that you are working on the glTF asset pipeline: https://www.youtube.com/watch?v=Q5Jj1c_F6QA

Between 7:15 to 7:40 in the video you mention that you set up a system in Blender to specify physics collision primitives. I have already done this on the Godot side via the OMI_physics_body glTF extension. In fact, it’s already merged into the engine, and is already in the currently released 4.3 version. Godot PR here GLTF: Update `OMI_physics_body`, add `OMI_physics_shape`, keep `OMI_collider` by aaronfranke · Pull Request #78967 · godotengine/godot · GitHub and glTF extension specification here gltf-extensions/extensions/2.0/OMI_physics_body at OMI_environment_sky · aaronfranke/gltf-extensions · GitHub Also, my friends at GD3D are working on a Blender addon called Bless which provides the capability to export glTF files from Blender with this physics data. You can find that project here GitHub - gd-3d/bless: blender level editor software suite

At 9:00 in the video I can tell that Blender Studio is currently not using our OMI physics system because you have a node named @CollisionShape3D@23577 and our system ensures that shape nodes have human-readable node names. It would improve interoperability and make things easier for you if we work together on this, so you avoid repeating work that we have already done.

I also saw that you are working on animations. I also recently implemented the KHR_animation_pointer glTF extension, which is already merged into Godot’s master branch and will be available in the upcoming Godot 4.4 release in a few weeks. Godot PR here https://github.com/godotengine/godot/pull/94165 and glTF extension specification here glTF/extensions/2.0/Khronos/KHR_animation_pointer at main · KhronosGroup/glTF · GitHub

@warcanin

Well glTF and godot have one issue, they are considered as scene, so to be able to use a mesh as a “part” you will need to save as mesh on import wich is annoying.

See this proposal: Allow importing a 3D model file as a mesh resource (or material/etc) instead of a scene · Issue #7494 · godotengine/godot-proposals · GitHub

@redmser

GODOT_* glTF extensions for storing Godot-specific data in glTF data (such as to decide whether an object should be used for collision or not).

For collision, we don’t need a GODOT_* extension, since we have OMI_* extensions for this already merged into Godot 4.3, plus there is some work towards making these KHR_* extensions.

@Ignawesome

Furthermore, many 3D models have to be put into collections to be turned into an asset because they are composed of several meshes. However, .gltf export does not support collections, so Godot does not see them, and some degree of restructuring (reparenting, empties, etc.) needs to be added.

This can be solved with glTFX (formerly known as glXF) which allows multiple scenes to be composed together. Blender should add the ability to export one .blend file with 3 collections as 3 glTF files linked together with one glTFX. As for the Godot side, I’ve already made a complete implementation as a GDScript addon here: GitHub - aaronfranke/godot-gltfx-reference-format: Godot implementation of the glTFX Reference Format, also known as glTF External Reference, glTF Experience Format, or glXF: https://github.com/KhronosGroup/glTF-External-Reference (it’s not part of the engine yet because glTFX is a Khronos effort and it is still in draft stage).