[VisionGlass] WebXR fixes

[svillar]

This PR reenables WebXR rendering in VisionGlass port. It also brings some interesting fixes like:

• controller has now a valid position in WebXR
• a 3D model of the controller is shown (from the WebXR registry) if none is rendered by the experience
• removed the sitting to standing transform which was moving the head position way too high

[svillar]

We can now create the WebXR session, but I think it doesn't work as it should. I've tried with Moonrider and XR Dinosaurs and in both I can observe the same issues:

1- I don't see the interstitial widget

Right I have seen that too, but I think we can handle it in a separate PR

2- Once in the WebXR session, the 3D space is too close to the user's view, so it's very difficult to interact with the world.

That's because of the patch that removes the sitting to standing transform. However that heavily depend on the experience, for example try the webxr samples.

3- The emulated controller is not synced with the mobile

I don't understand what this means. In the dinosaurs case I can use the controller to point to UI elements normally.

[javifernandez]

I don't understand what this means. In the dinosaurs case I can use the controller to point to UI elements normally.

I'll try to explain better the weird effect I notice on the pointer; when I move the mobile horizontally, the controller does it is diagonally. However, this happens when I rotate my perspective 90 degrees. As discussed offline, this looks like a calibration issue and indeed I managed to reproduce it in a 2D environment.

It seems that when the user's perspective is rotated 90 degrees a new calibration is needed; otherwise the error introduced will be transferred to the WebXR session.

[javifernandez]

I'll describe now other issues related to the positioning on the 3D world proposed in the WebXR session, specifically in the Dinosaurs XR game.

When I enter the game, my position is rotated 180 degrees in the x axis. The UI elements to select the dinosaurs are on my back. This issue forces me to move my perspective, with the corresponding calibration errors introduced by the mobile. Give that it's not possible (is this a bug ?) to calibrate the pointer inside the WebXR session, it makes the game barely usable.

[svillar]

I don't understand what this means. In the dinosaurs case I can use the controller to point to UI elements normally.

I'll try to explain better the weird effect I notice on the pointer; when I move the mobile horizontally, the controller does it is diagonally. However, this happens when I rotate my perspective 90 degrees. As discussed offline, this looks like a calibration issue and indeed I managed to reproduce it in a 2D environment.

It seems that when the user's perspective is rotated 90 degrees a new calibration is needed; otherwise the error introduced will be transferred to the WebXR session.

Yes that's well know. The accelerometer of the phone aggregates errors as you move away from the original location. As I mentioned this has nothing to do with being inside a WebXR session. This can be seen in the 2D environment, that's why we need recalibration.

[javifernandez]

But the actual problem is that the WebXR experience starts in the opposite direction; the UI elements are on my back.

[svillar]

Ok, lets merge this, but we need to investigate the orientation issues.

OK I'll merge the first 4 commits and leave the last one aside. It'll be part of a followup with fixes for the orientation issues.