WebXR: Added XRButton

[mrdoob]

Description

Adds a new XRButton class which creates a immersive-ar or a immersive-vr session depending on availability.

This allows making projects that run in passthrough headsets and also on vr headsets.

Side note:
I wonder if it was a mistake to call immersive-ar to the session that mobile phones support.
Maybe it should have been called mobile-ar?

/cc @toji @cabanier @elalish

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

Filesize	Gzipped	Diff from dev
633.7 kB	157 kB	+88 B

🌳 Bundle size after tree-shaking

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

Filesize	Gzipped	Diff from dev
424.9 kB	103 kB	+88 B

[cabanier]

LGTM

[cabanier]

LGTM

[cabanier]

Most of these experiences are VR only. Maybe there should be a way to prefer VR instead of AR for such sites.

[mrdoob]

What makes you think they are VR only?

The problem is that I've not figured out how to make the background transparent without passing alpha: true to the renderer yet 😅

WIP

[cabanier]

What makes you think they are VR only?

The problem is that I've not figured out how to make the background transparent without passing alpha: true to the renderer yet 😅

Can you not set a background? WebXR are cleared to transparent black.

[mrdoob]

Ok, figured it out...
Turns out there was some code around for it already.

[cabanier]

So this is a new button that prefers AR mode? If so LGTM

[cabanier]

LGTM. It doesn't look like I have permission to officially sign off