webxr

See:
https://forum.babylonjs.com/t/can-gltf-export-a-specific-mesh-from-scene/10641/3

Repro:
https://www.babylonjs-playground.com/#YBEKDT#4

Expected result:
Fan materials and textures should not be included in exported glTF from this playground.

Running the tabs default launch command (-t) does not respect redirects at the target.

$ node . -t https://aframe.io/a-painter

☝️ The above will error, even though the server will redirect to https://aframe.io/a-painter/ and serve HTML there:

$ curl -i https://aframe.io/a-painter
HTTP/1.1 301 Moved Permanently
Date: Mon, 03 Jun 2019 20:10:27 GMT
Content-Type: text/ht

You should be able to add text to a scene. Either as a Text Geometry or SDF text, probably both.

There's already a text component in AFrame that we can use in Hubs. We would need to add a new Spoke node with the ability to preview the text.

I think we should export the following properties:

value
align
anchor
baseline
color
he

Noticed the right half of the keyboard works correctly for transparency during hover, but the left side keys show a black background on hover. The keys circled below are the ones tested as having this issue.

![moonkeyboard](https://user-images.githubuserco

Ideally we will have a gltf for each device, but in the meantime we could use a generic VR input device like https://poly.google.com/view/cUT5C1Krx7g or https://poly.google.com/view/0n5B6e5lYZe

AppImage --help lists a parameter "--help-all". I tried running that but it just ran the client. I tried running with both "--help" and "--help-all", but output was the same as from "--help". I have also read people discussing other parameters that are not mentioned in the --help output and they did not seem interested in adding to it. I think it's important that all functional parameters be outpu

It would be awesome to have a sick 3d loading screen, maybe something that fades from a blank 3d scene with a 3d loading icon into the scene as it loads.