VRDisplay.requestPresent()

This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The requestPresent() method of the VRDisplay interface starts the VRDisplay presenting a scene.

Syntax

vrDisplayInstance.requestPresent(layers).then(function() {
  // Do something after the presentation has begun
});

Parameters

layers
An array of VRLayerInit objects representing the scene you want to present. At the moment, this can be a minimum of 0 and a maximum of 1.

Return value

A promise that resolves once the presentation has begun. there are a number of rules surrounding the promise's fulfillment or rejection:

  • If VRDisplayCapabilities.canPresent is false, or if the VRLayer array contains more than VRDisplayCapabilities.maxLayers layers, the promise will be rejected.
  • If the VRDisplay is already presenting when requestPresent() is called, the VRDisplay will update the VRLayer array being presented.
  • If a call to requestPresent() is rejected while the VRDisplay is already presenting it will end its presentation.
  • If requestPresent() is called outside of an engagement gesture the promise will be rejected unless the VRDisplay was already presenting. This engagement gesture is also sufficient to allow requestPointerLock() calls until presentation has ended.

Examples

if(navigator.getVRDisplays) {
  console.log('WebVR 1.1 supported');
  // Then get the displays attached to the computer
  navigator.getVRDisplays().then(function(displays) {
    // If a display is available, use it to present the scene
    if(displays.length > 0) {
      vrDisplay = displays[0];
      console.log('Display found');
      // Starting the presentation when the button is clicked: It can only be called in response to a user gesture
      btn.addEventListener('click', function() {
        if(btn.textContent === 'Start VR display') {
          vrDisplay.requestPresent([{ source: canvas }]).then(function() {
            console.log('Presenting to WebVR display');

            // Set the canvas size to the size of the vrDisplay viewport

            var leftEye = vrDisplay.getEyeParameters('left');
            var rightEye = vrDisplay.getEyeParameters('right');

            canvas.width = Math.max(leftEye.renderWidth, rightEye.renderWidth) * 2;
            canvas.height = Math.max(leftEye.renderHeight, rightEye.renderHeight);

            // stop the normal presentation, and start the vr presentation
            window.cancelAnimationFrame(normalSceneFrame);
            drawVRScene();

            btn.textContent = 'Exit VR display';
          });
        } else {
          vrDisplay.exitPresent();
          console.log('Stopped presenting to WebVR display');

          btn.textContent = 'Start VR display';

          // Stop the VR presentation, and start the normal presentation
          vrDisplay.cancelAnimationFrame(vrSceneFrame);
          drawScene();
        }
      });
    }
  });
}

Note: You can see this complete code at raw-webgl-example.

Specifications

Specification Status Comment
WebVR 1.1
The definition of 'requestPresent()' in that specification.
Editor's Draft Initial definition

Browser compatibility

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support Yes1 2 Yes

553

584

No ? ?
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidIE mobileOpera AndroidiOS Safari
Basic support No Yes5 ? ? No ? ?

1. Only works on desktop in an experimental version of Chrome (other builds won't return any devices when Navigator.getVRDisplays() is invoked).

2. This feature is behind the WebVR preference. To change preferences in Chrome, visit chrome://flags.

3. Windows support was enabled in Firefox 55.

4. macOS support was enabled in Firefox 58.

5. Currently supported only by Google Daydream.

See also

Document Tags and Contributors

 Contributors to this page: fscholz, chrisdavidmills, abbycar
 Last updated by: fscholz,