TSL: Do not auto-generate tangent attribute.

[Mugen87]

Fixed #32198.

Description

Computing a tangent attribute when building nodes corrupts the cache key and leads to confusing behavior like described in #32198. For a more consistent behavior, it's better to let the application compute tangent vectors if they are missing in geometry data. Developers might prefer to use BufferGeometryUtils.computeMikkTSpaceTangents() anyway for tangent computation.

Removing the auto-generation triggers below warning if tangent are missing so users should be informed about what's going on:

THREE.AttributeNode: Vertex attribute "tangent" not found on geometry.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	356.24 86.47	356.24 86.47	+0 B +0 B
WebGPU	610.57 171.28	610.49 171.27	-81 B -15 B
WebGPU Nodes	609.18 171.02	609.1 171.01	-81 B -16 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	487.87 121.22	487.87 121.22	+0 B +0 B
WebGPU	679.35 186.51	679.27 186.49	-81 B -23 B
WebGPU Nodes	621.07 169.69	620.99 169.67	-81 B -17 B

[sunag]

It would be good if we had an automatic alternative for tangents soon, this should make things easier since most node systems and 3D software do this, and since most models don't have tangents exported, it would still be compatible with alternatives like MikkTSpace since it will only generate them automatically if there are no options available.