WebGL context must be marked as XR compatible in order to use with an immersive XRSession

[ranbuch]

When calling WebXRManager.setSession( value ) you sometimes might get this message:

Uncaught (in promise) DOMException: Failed to construct 'XRWebGLLayer': WebGL context must be marked as XR compatible in order to use with an immersive XRSession

To Reproduce

I am able to reproduce the issue only on my localhost environment. When serving my viewer from the server it's working fine.

The reason for this issue is a racing condition.

when creating an instance of XRWebGLLayer the WebGL context (gl) should already be XR compatible enabled.

The gl.makeXRCompatible() function returns a Promise.

Current setSession Code

	this.setSession = function ( value ) {

		session = value;

		if ( session !== null ) {

			session.addEventListener( 'select', onSessionEvent );
			session.addEventListener( 'selectstart', onSessionEvent );
			session.addEventListener( 'selectend', onSessionEvent );
			session.addEventListener( 'squeeze', onSessionEvent );
			session.addEventListener( 'squeezestart', onSessionEvent );
			session.addEventListener( 'squeezeend', onSessionEvent );
			session.addEventListener( 'end', onSessionEnd );

			const attributes = gl.getContextAttributes();

			if ( attributes.xrCompatible !== true ) {

				gl.makeXRCompatible();

			}

			const layerInit = {
				antialias: attributes.antialias,
				alpha: attributes.alpha,
				depth: attributes.depth,
				stencil: attributes.stencil,
				framebufferScaleFactor: framebufferScaleFactor
			};

			// eslint-disable-next-line no-undef
			const baseLayer = new XRWebGLLayer( session, gl, layerInit );

			session.updateRenderState( { baseLayer: baseLayer } );

			session.requestReferenceSpace( referenceSpaceType ).then( onRequestReferenceSpace );

			//

			session.addEventListener( 'inputsourceschange', updateInputSources );

		}

	};

Suggested setSession Code

	this.setSession = function ( value ) {

		session = value;

		if ( session !== null ) {

			session.addEventListener( 'select', onSessionEvent );
			session.addEventListener( 'selectstart', onSessionEvent );
			session.addEventListener( 'selectend', onSessionEvent );
			session.addEventListener( 'squeeze', onSessionEvent );
			session.addEventListener( 'squeezestart', onSessionEvent );
			session.addEventListener( 'squeezeend', onSessionEvent );
			session.addEventListener( 'end', onSessionEnd );

			const attributes = gl.getContextAttributes();

			const setSession = function() {
				const layerInit = {
					antialias: attributes.antialias,
					alpha: attributes.alpha,
					depth: attributes.depth,
					stencil: attributes.stencil,
					framebufferScaleFactor: framebufferScaleFactor
				};
	
				// eslint-disable-next-line no-undef
				const baseLayer = new XRWebGLLayer( session, gl, layerInit );
	
				session.updateRenderState( { baseLayer: baseLayer } );
	
				session.requestReferenceSpace( referenceSpaceType ).then( onRequestReferenceSpace );
	
				//
	
				session.addEventListener( 'inputsourceschange', updateInputSources );
			};

			if ( attributes.xrCompatible !== true ) {

				gl.makeXRCompatible( setSession );

			} else {

				setSession();

			}

		}

	};

Screenshots

Platform:

• Device: Mobile (Samsung Galaxy S20 Ultra - Exynos variant)
• OS: Android 11
• Browser: Chrome Canary 89.0.4329.2
• Three.js version: dev, r122

I can create a pull request myself, I just remember that the way to do is on this repo isn't so straghtfarward.

Fork dev?

Build and then push?

If someone wants to do it be my guest. If not, please provide a link or explains how to do it right.

Thanks.

[Mugen87]

Does setSession() has to be sync? If it is declared as async, it should be sufficient to change the call to:

await gl.makeXRCompatible();

[ranbuch]

setSession() is not currently declered as async.

If however you will change setSession() to async you should consider also this change:

	session.addEventListener( 'inputsourceschange', updateInputSources );

	await session.requestReferenceSpace( referenceSpaceType );

	onRequestReferenceSpace();

instead of this:

	session.updateRenderState( { baseLayer: baseLayer } );

	session.requestReferenceSpace( referenceSpaceType ).then( onRequestReferenceSpace );

	//

	session.addEventListener( 'inputsourceschange', updateInputSources );

XRSession.requestReferenceSpace does return a Promise.

In general, we don't have to detect when the session is ready because we are getting the frame from the WebXRManager.setAnimationLoop callback.

In case it's not ready the frame parameter is falsely.

[mrdoob]

@toji what do you think?

[sjpt]

Is there a significant overhead in makeXRCompatible()?
Why not just call it when the renderer is created and context established?

[Mugen87]

Some context: #19275

[toji]

The suggested code change for setSession() looks good. It definitely needs to wait for the makeXRCompatible() call to complete prior to creating the XRWebGLLayer() for correctness.

[toji]

Is there a significant overhead in makeXRCompatible()?

It may cause context loss/restore, primarily on multi-GPU devices. That probably qualifies as "significant overhead"

Why not just call it when the renderer is created and context established?

You don't want to do it blindly because it could cause inappropriate GPU switches for non-XR pages that don't require it. I do think that it should be something that can be requested when creating the renderer, though, because if you know the page will be displaying XR content that's the less disruptive path.

[sjpt]

Is there a significant overhead in makeXRCompatible()?

It may cause context loss/restore, primarily on multi-GPU devices. That probably qualifies as "significant overhead"

Thank you for the clarification, makes complete sense.

[mat-lo]

I get the same error on all the WebXR AR examples (cones, hittest and paint), I can't run any of them currently.
Pixel 4 XL on Chrome Canary 89.0.4336.0

Uncaught (in promise) DOMException: Failed to construct 'XRWebGLLayer': WebGL context must be marked as XR compatible in order to use with an immersive XRSession
    at WebXRManager.setSession (https://threejs.org/build/three.module.js:22258:22)
    at onSessionStarted (https://threejs.org/examples/jsm/webxr/ARButton.js:16:17)

[Mugen87]

The first step to solve this issue is to get #20761 in. After that we can use async/await syntax in #20754.

[jpryne]

Just upgraded to Chrome 88.0.4324.96 & I'm facing this issue starting a WebXR session in 𝚕̶𝚘̶𝚌̶𝚊̶𝚕̶𝚑̶𝚘̶𝚜̶𝚝̶ testing. Windows 10 64, Oculus Rift CV1

Correction: This is broken when loading the examples from the server too. As of updating to Chrome 88, I can no longer view ThreeJS-VR in Chrome. I can however still enter WebXR at https://immersive-web.github.io/webxr-samples/

ThreeJS Examples are working fine in Microsoft Edge.