Shaders: Add support for transforming instanced mesh tangents

[gkjohnson]

Fix #27116

Description

• Pulls the "transformedTangent" variable to the beginning of the shader block.
• Ensure the batched geometry block modifies "transformedNormal" and "transformedTangent" rather than the "objectNormal" and "objectTangent" variants.
• Ensure instanced geometry correct transform tangents.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

Filesize dev	Filesize PR	Diff
655 kB (162.2 kB)	655.1 kB (162.2 kB)	+83 B

🌳 Bundle size after tree-shaking

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

Filesize dev	Filesize PR	Diff
447.6 kB (108.2 kB)	447.7 kB (108.2 kB)	+83 B

[Mugen87]

LGTM!

@WestLangley We are doing the right thing here, correct 😇 ? Tangents should be transformed by instancing/batching similar to normals.

[WestLangley]

@WestLangley We are doing the right thing here, correct 😇 ? Tangents should be transformed by instancing/batching similar to normals.

I don't think so. Transformed normals should remain orthogonal to the plane of the face; transformed tangents should remain within the plane of the face.

[gkjohnson]

I don't think so. Transformed normals should remain orthogonal to the plane of the face; transformed tangents should remain within the plane of the face.

Oops you're right 😅 The tangents still need to have the instance and batching matrices applied, though. I've updated the PR to remove the additional scaling logic only needed for normals.