BufferGeometry: Renamed uv2, uv3, uv4 to uv1, uv2, uv3

[mrdoob]

Related issue: #25788 #25938

Description

Before this PR we had this setup:

GLTF	channel	attribute
TEXCOORD_0	0	uv
TEXCOORD_1	1	uv2
TEXCOORD_2	2	uv3
TEXCOORD_3	3	uv4

This PR renames the attributes to match GLTF ids and material.channel:

GLTF	channel	attribute
TEXCOORD_0	0	uv0 uv
TEXCOORD_1	1	uv1
TEXCOORD_2	2	uv2
TEXCOORD_3	3	uv3

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

Filesize dev	Filesize PR	Diff
634.5 kB (157.3 kB)	634.5 kB (157.3 kB)	+12 B

🌳 Bundle size after tree-shaking

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

Filesize dev	Filesize PR	Diff
425.6 kB (103.2 kB)	425.7 kB (103.2 kB)	+12 B

[mrdoob]

The uv to uv0 warnings make webgl_geometry_csg super slow.
Maybe we don't really need the warnings...

[mrdoob]

I've updated all the code locally and I'm not loving this new pattern:

 		this.setAttribute( 'position', new Float32BufferAttribute( vertices, 3 ) );
 		this.setAttribute( 'normal', new Float32BufferAttribute( normals, 3 ) );
-		this.setAttribute( 'uv', new Float32BufferAttribute( uvs, 2 ) );
+		this.setAttribute( 'uv0', new Float32BufferAttribute( uvs, 2 ) );

I think for now I'm just going to go for this:

GLTF	channel	attribute
TEXCOORD_0	0	uv
TEXCOORD_1	1	uv1
TEXCOORD_2	2	uv2
TEXCOORD_3	3	uv3

[mrdoob]

Hmm, I'm having a hard time trying to predict the side effects of this code:

// Backwards compatibilty

Object.defineProperties( this.attributes, {
	'uv2': {
		set: function ( value ) {

			if ( this.uv1 === undefined ) {

				console.warn( 'THREE.BufferGeometry: The attribute uv2 has been renamed to uv1.' );
				this.uv1 = value;

			}

			delete this.uv2;

		},
		configurable: true
	}
} );

I feel this code may break more things than fix...
It may be better to not have it for now and release a patch version when we gather more use cases.

[LeviPesin]

Maybe add deprecation comment // @deprecated, r152 here?

[LeviPesin]

I still think this function would be simpler just as

return value === 0 ? 'uv' : `uv${ value }`;

... Just as you did with the FBXLoader.

[mrdoob]

Now that the ids are the same the code is more readable yes.