TSL: Add batchIndirectIndex.

[Mugen87]

Fixed #33477.

Description

The PR introduces the TSL object batchIndirectIndex that allows access tot he indirect index of a batched mesh.

@John-D-a-i @MicolaL Would this work for your use cases?

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	365.88 86.71	365.88 86.71	+0 B +0 B
WebGPU	685.67 189.48	685.74 189.52	+74 B +37 B
WebGPU Nodes	683.65 189.16	683.73 189.19	+74 B +36 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

	Before	After	Diff
WebGL	510.55 124.02	510.55 124.02	+0 B +0 B
WebGPU	764.04 205.54	764.09 205.54	+52 B +4 B
WebGPU Nodes	713.54 192.96	713.59 192.97	+52 B +14 B

[github-actions]

🖼️ E2E screenshot tests

❌ 1 example(s) failed (full artifacts).

Example	Expected	Actual	Diff
webgpu_animation_retargeting

[John-D-a-i]

Fixed #33477.

Description

The PR introduces the TSL object batchIndirectIndex that allows access tot he indirect index of a batched mesh.

@John-D-a-i @MicolaL Would this work for your use cases?

On my end, all I need is to obtain the instance ID of the BatchedMesh. I'll give it a try after it's released. Is it necessary to pass the BatchedMesh object, or will the material automatically recognize it?

[Mugen87]

I would be great if you could patch your local version with this change and make a test. It won't be merged without a test.

You don't need to pass the the batched mesh. batchIndirectIndex is not a TSL function. It's an accessor object similar to vertexIndex or instanceIndex and used in the same way.