How to generate uv attribute for buffer geometry (mesh)

[trusktr]

Generating UVs can be useful for procedural/generated geometries (the same as with defining UVs for Three’s out-of-the-box geometries).

There isn’t quite enough documentation on what the rules are for the UV attribute (indexed vs non-indexed geometry), so I made a thread on that:

Documentation: Do UVs need to match with position attribute? Or index attribute?

Unless I missed it, I didn’t see the docs describing the rules for UV attributes. For example, does the uv attribute need to match with position or with index (indexed geometry vs non-indexed geometry)?