The webxr example is broken when enabling VR

[AnthonyGlt]

Since the bump of the three.js version f7303de
The view_3d_map_webxr example doesn't work anymore when entering the VR mode

Screencast.from.04-12-2024.17.30.28.webm

Context

Steps to Reproduce

1. Run the view_3d_map_webxr example
2. Click on Enter VR
3. Blank screen

Possible Cause/Fix/Solution

Since this merge in three.js, there is a condition on matrixWorldAutoUpdate .

To fix it, we should somehow set
view.scene.matrixWorldAutoUpdate = true;
either in the file view_3d_map_webxr.html
or in WebXR.js, using this kind of workaround
So in WebXR.js , above these lines

itowns/src/Renderer/WebXR.js

Lines 55 to 57 in 683e55d

	view.camera.camera3D.updateMatrix();
	view.camera.camera3D.updateMatrixWorld(true);
	view.notifyChange(view.camera.camera3D, true);

we could add

                const prevMatrixWorldAutoUpdate = view.scene.matrixWorldAutoUpdate;
                view.scene.matrixWorldAutoUpdate = true;
                view.scene.updateMatrix();
                view.scene.updateMatrixWorld();
                view.scene.matrixWorldAutoUpdate = prevMatrixWorldAutoUpdate;

[jailln]

I wonder how there aren't more things broken as I read the comments from mrdoob/three.js#28533.

In my opinion, we should harmonize the xr and non-xr behaviour: either set autoupdate to false in both cases and manage matrices updates ourselves, or set autoupdate to true for both context.

I haven't looked into it yet but first we need to remember why we set the autoupdate to false and if there's really a performance gain or if we'd be better off setting it to true and avoiding the hassle and bugs.

@Desplandis wdyt?

[AnthonyGlt]

It should be noted that we set scene.matrixWorldAutoUpdate = false; in View.js

itowns/src/Core/View.js

Lines 193 to 195 in 683e55d

	if (!options.scene3D) {
	this.scene.matrixWorldAutoUpdate = false;
	}

[jailln]

After discussing it online, we need to check:

• what is the real perf gain of setting matrixWorldAutoUpdate to true in the context of itowns (measure it)
• decide if we set it to true or find a pattern to set it to false and avoid bugs