VREyeParameters

The VREyeParameters interface of the WebVR API represents all the information required to correctly render a scene for a given eye, including field of view information.

This interface is accessible through the VRDisplay.getEyeParameters() method.

VREyeParameters.offset  Read only

Represents the offset from the center point between the user's eyes to the center of the eye, measured in meters.

VREyeParameters.fieldOfView  Read only

Describes the current field of view for the eye, which can vary as the user adjusts their interpupillary distance (IPD).

VREyeParameters.renderWidth Read only

Describes the recommended render target width of each eye viewport, in pixels.

VREyeParameters.renderHeight Read only

Describes the recommended render target height of each eye viewport, in pixels.

navigator.getVRDisplays().then(function(displays) {
  // If a display is available, use it to present the scene
  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() {
    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);

      drawVRScene();
    });
  });
});

• WebVR API homepage
• https://mixedreality.mozilla.org/ — demos, downloads, and other resources from the Mozilla VR team.