MeshSurfaceSampler: Add uv support.

[makc]

this is one of two changes I had to do to MeshSurfaceSampler in order to use it for the grass effect - let's see if it makes sense to you, and then I will maybe come back with the other one

[gkjohnson]

At some point this function should really just return a barycoord value and face index so users can interpolate between whatever buffer attributes they want to. Adding a new argument for every possible buffer attribute doesn't seem sustainable 😅

[Mugen87]

I'm afraid not all users know how to do the interpolation correctly. Maybe better when MeshSurfaceSampler takes care about this.

[LeviPesin]

Maybe we can add another method that does just that (i.e. returns barycoords and index)? So we can have both.

[donmccurdy]

Adding that method (sampleBarycentric?) would be ideal I think, though I'm also fine with this PR as a starting point.

EDIT: Related –

• Surface sample texture with Color from texture #24629 (comment)

[makc]

Oh I did not see 24629. Maybe I could borrow the docs thing from there 🤔

[makc]

that's weird, I did add the commit by @IanSweeneyAC but it does not appear in this PR... edit: so I was hit by this

[makc]

and now there is failed webxr_vr_sandbox screenshot. not my fault, lol

[Mugen87]

Don't worry about this example. It frequently fails in other PRs, too. Maybe regenerating the screenshots would help.

[LeviPesin]

Maybe we should add that example to the exceptions?

(The number of exceptions starts to be really large... I should look into it and see what can be fixed (e.g. setIntervals), also need to remove BrowserFetcher for Puppeteer 20)