TSL: Fix instance() usage with velocity.

[Mugen87]

Related issue: -

Description

I'm currently doing some deeper testing with VelocityNode. Turns out the node does not work with instancing yet since positionPrevious has no valid value per instance so far. The PR fixes that by honoring the instance matrix in positionPrevious.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	336.36 78.34	336.36 78.34	+0 B +0 B
WebGPU	533.07 148.15	533.11 148.16	+35 B +13 B
WebGPU Nodes	532.54 148.05	532.57 148.06	+35 B +13 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	465.37 112.21	465.37 112.21	+0 B +0 B
WebGPU	604.68 164.12	604.72 164.13	+35 B +14 B
WebGPU Nodes	559.67 153.56	559.71 153.57	+35 B +10 B

[sunag]

@Mugen87 Do you think we can use the TSL prefix and names in the title instead of the Nodes names? It seems to be easier for the end user to see the fixes and improvements of TSL in each release.

[Mugen87]

Yes, we can do that. That also means the release notes need a new TSL section that lists such changes.

[sunag]

Yes, we can do that. That also means the release notes need a new TSL section that lists such changes.

Yes, good idea.
What do you think about using this pattern for now?

TSL: Fix instance() usage with velocity.

[Mugen87]

LGTM! 👍

[Mugen87]

Doing some more testing and I've realized this fix isn't 100% correct. To get the real positionPrevious when using instancing, we have to apply the instanceMatrixNode version from the previous frame. Similar to SkinningNode, we need a pendant for previousBoneMatricesNode. So previousInstanceMatrixNode and all instance matrices from the previous frame.

Besides, we need this in all modules that apply any kind of vertex transformation. E.g.: MorphNode also needs a fix otherwise the velocity isn't correct and breaks anything using it like Motion Blur and TRAA.

Um, maintaining all these "previous" data is not really a scalable solution. When users modulate positionLocal in their app, they automatically break velocity computation.

[sunag]

E.g.: MorphNode also needs a fix otherwise the velocity isn't correct and breaks anything using it like Motion Blur and TRAA.

We should calculate the vertexes in the compute stage, similar to what was done in this example. I think it should improve performance as well, and it is the general solution for this.