EXT_mesh_gpu_instancing - Support multiple primitives mesh

[Pourfex]

Hello ! Using a glb and transforming it with gltf-transform (https://github.com/donmccurdy/glTF-Transform) in 2 steps :

• dedup (after we used gltf-transfor inspect and we do see several meshes that have many instances - max 102)
• instance (the one that enable EXT_mesh_gpu_instancing)

We are able to see correct result in babylon.js (in the sandbox) and unity (using GLTFast : https://github.com/atteneder/glTFast).

We we're not able to see the correct results in threejs using your code :

Here is the glb that uses EXT_mesh_gpu_instancing: 01_batiment_instance.glb.zip

And thanks for developing this extension for threejs users :)

[takahirox]

Thanks for the bug report. Let me look into it...

[takahirox]

Perhaps this is the cause.

https://github.com/takahirox/three-gltf-extensions/blob/99af44c234b61378cbfbc11dd34fd9831c8af5a4/loaders/EXT_mesh_gpu_instancing/EXT_mesh_gpu_instancing.js#L46-L49

The loader extension plugin doesn't support multiple primitives mesh yet. If we implement multiple primitive mesh support, probably the model will be able to be rendered correctly.

[takahirox]

I started to work on the multiple primitives mesh support.

@Pourfex I have a question for your 01_batiment_instance.glb model. The values of the TRANSLATION attribute seem to be very huge like (1351130.625, 62.75, -6240384). Do you know if it's intentional? Or may it be a Three.js glTF loader bug?

[Pourfex]

Thanks for looking at it.

Indeed the model was georeferenced (real world coordinates). I uploaded a 0-0-0 centered version of it here :

01_batiment_instance.glb.zip

Now you'll see all elements that are not using GPU Instancing because they are not duplicates at the correct position. However I think that elements using GPU Instancing are not in the correct position (they are centered at 0,0,0 position I think).

If you need any more test files, I can provide a lot more.

Thanks again to develop this for community. Best.

[takahirox]

I merged #58. Does it look good?

[Pourfex]

Looks great for this file !

We tested the latest code (merge #58 ) on some files and we couldn't see anything.

I can provide you this one file that is not showing yet : house_berlin_instance.glb.zip

And thanks again to work on this !

[takahirox]

The TRANSLATION attribute of that model seems very huge like [-4962.7080078125, -10806.2001953125, 10240.83203125]. If it's intentional, probably the model can be displayed if you adjust camera?

[Pourfex]

Had to manipulate the file a little to have correct translation, but yeah it's working with your merge.

Tried 2 others files and they seems to work as expected. File tested : 5_house_berlin_instance

Thanks for the merge, closing issue now.