Skinning Shaders: Remove need skinning texture size uniform by using textureSize function

[gkjohnson]

Related issue: --

Description

Similar to what's used in batching - use the textureSize function to get the texture size, instead. WebGL2 only but Skinning already requires webgl 2.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

Filesize dev	Filesize PR	Diff
653.4 kB (161.9 kB)	653.1 kB (161.8 kB)	-310 B

🌳 Bundle size after tree-shaking

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

Filesize dev	Filesize PR	Diff
446 kB (107.9 kB)	445.8 kB (107.8 kB)	-264 B

[Mugen87]

but Skinning already requires webgl 2.

This is actually not true. I have also forgot this but skinning did work with WebGL 1 when OES_texture_float and vertex textures were supported. This is also documented (see https://threejs.org/docs/index.html#api/en/objects/SkinnedMesh).

With this PR, skinning support for WebGL 1 was completely stopped. A user complains now in the forum: https://discourse.threejs.org/t/r159-use-skinning-webgl1-error/58872

WebGL 1 support should be stopped with r163 but I wonder if this change was a bit premature 🤔 .

[Mugen87]

The thing is I've seen devs already migrating their custom skinning code to the new version (#27291), so reverting would produce even more confusion.

It's a bit unfortunate but I think it's best if we stick to this change and just mentioned in the migration guide that skinning does not work anymore with WebGL 1.

[gkjohnson]

Sorry this was my mistake - I'd forgotten that WebGL 1 could support those features.

It's a bit unfortunate but I think it's best if we stick to this change and just mentioned in the migration guide that skinning does not work anymore with WebGL 1.

I think I agree with this.

[Mugen87]

@arpu Out of curiosity: What are doing in your project when we stop WebGL 1 support in r163? Will you modify your fork of three.js to keep WebGL 1? Why do you still need it in your project?

[arpu]

@Mugen87 the idea was to remove support for ios 14 ( webgl1) with r163 and switch to the new webgpu/webgl2 renderer