Export Particle System to EXT_mesh_gpu_instancing

I’m considering an experimental implementation of KHR_instancing (DRAFT), using Blender’s Particle Systems as the source. The glTF extension is not certainly not meant to reproduce the full functionality of a particle system in any particular software (that would be … challenging 😅) but it does provide a very efficient way to have large quantities of the same mesh in a scene, with per-instance transforms and other custom data attached.

Proposal:

• Export a Particle System emitting a Mesh as a static KHR_instancing batch.
• Include Custom Data Layers to write custom attributes on the batch (_INDEX, _VALUE) so that shaders in the viewing application can add variance to materials, identify instances, etc.

I have no plan to include animation at this time; baking and efficiently storing the various animation types and simulations that can be applied to Particle Systems is well beyond what I want to attempt right now.

Example (viewer) implementation in three.js:

[PirateJC]

Another option, not implemented — Blender has a separate “instancing” mechanism for objects scattered around a scene to reuse mesh or other data. We export those without duplicating the geometry already (great!) although it could be even more efficient with KHR_instancing. However, KHR_instancing would lose these objects’ positions in the scene graph. I think that type of opinionated optimization might be more appropriate for a post-export optimization tool, like gltfpack or glTF-Pipeline.

I’d love to add my vote for this. Blender’s Object Scatter add-on allows for a very artist friendly workflow for instancing objects while being able to easily “paint” the instances where you’d like them to go. It would be amazing if the gltf exporter could read that scatter data (duplicators) and do the necessary conversions to gltf.

Thanks for all the work on this!

[takahirox]

FYI: I wrote an addon that allows to export instanced geometries created with Geometry Nodes, not particle systems, as glTF with EXT_mesh_gpu_instancing extension.

https://github.com/takahirox/glTF-Blender-IO-EXT-mesh-gpu-instancing

It’s still an early prototype and I’m not sure if this is the best approach, and I’m not sure how the extension should be imported yet tho.

https://github.com/takahirox/glTF-Blender-IO-EXT-mesh-gpu-instancing/issues/2