WebGPURenderer, NodeMaterial: same variant between different Skeletons?

[0b5vr]

Description

Currently, the NodeMaterial system creates different shader program variants between different skeletons, resulting in a long compilation time.
Is it possible to use the same program variant between skinned mesh with different skeletons?

Related: #27398

Context:

In three-vrm, we are using a function called removeUnnecessaryJoints, which generates skeletons for each mesh to prevent exceeding the maximum uniform count on mobile devices.

The function body:
https://github.com/pixiv/three-vrm/blob/v2.0.10/packages/three-vrm/src/VRMUtils/removeUnnecessaryJoints.ts

Solution

Currently, we are dispatching variants by adding skeleton uuid to the cache key.

three.js/examples/jsm/renderers/common/RenderObject.js

Line 136 in 841d2e7

cacheKey += object.skeleton.uuid + ',';

it would be nice if we could put a bone count instead and make it work properly, for example.
Probably we have to modify how we upload bone matrices as a uniform array? since it's not working as is.

Alternatives

Alternatively, I can change the removeUnnecessaryJoints to create less skeletons when there are many meshes but I'm yet to come up with a way.
I can align the bone count between skeletons by adding dummy bones at the tails of arrays.

Additional context

I think this is pretty much the bare minimum to check the behavior.

https://glitch.com/edit/#!/denim-valley-echinodon

[sunag]

it would be nice if we could put a bone count instead and make it work properly, for example.
Probably we have to modify how we upload bone matrices as a uniform array? since it's not working as is.

Sounds good define a bone count as part of cache key, I think that some modifications will be necessary in SkinningNode to this work properly, maybe manage reference nodes like we did in MorphNode, I will have to check that.

[0b5vr]

I think this is pretty much the bare minimum to check the behavior.

https://glitch.com/edit/#!/denim-valley-echinodon