VRDisplay.requestPresent()

This is an experimental technology
Because this technology's specification has not stabilized, check the compatibility table for usage in various browsers. Also note that the syntax and behavior of an experimental technology is subject to change in future versions of browsers as the specification changes.

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

Feature Chrome Edge Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support No support[1] (Yes) 55 (55)[2] No support No support No support
Feature Android Edge Firefox Mobile (Gecko) IE Phone Opera Mobile Safari Mobile Chrome for Android Samsung Internet for GearVR
Basic support No support No support 55.0 (55) No support No support No support (Yes)[3] (Yes)
 

[1] API Available on all platforms behind a flag, but currently only works on desktop in an experimental version of Chrome (other builds won't return any devices when Navigator.getVRDisplays() is invoked).

[2] Currently only Windows support is enabled by default. Mac support is available in Firefox Nightly.

[3] Currently supported only by Google Daydream.

See also

Document Tags and Contributors

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