VRFrameData.timestamp - Web APIs 编辑

Experimental

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

The timestamp read-only property of the VRFrameData interface returns a constantly increasing timestamp value representing the time a frame update occurred.

Timestamps are useful for determining if position state data has been updated from the hardware. Since values are monotonically increasing, they can be compared to determine the ordering of updates — newer values will always be greater than or equal to older values.

The timestamp starts at 0 the first time VRDisplay.getFrameData() is invoked for a given VRDisplay.

Syntax

var myTimestamp = vrFrameDataInstance.timestamp;

Value

A DOMHighResTimeStamp object.

Examples

var frameData = new VRFrameData();
var vrDisplay;

navigator.getVRDisplays().then(function(displays) {
  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() {
      drawVRScene();
    });
  });
});

// WebVR: Draw the scene for the WebVR display.
function drawVRScene() {
  // WebVR: Request the next frame of the animation
  vrSceneFrame = vrDisplay.requestAnimationFrame(drawVRScene);

  // Populate frameData with the data of the next frame to display
  vrDisplay.getFrameData(frameData);

  // grab the current timestamp on each run of the rendering loop
  // and do something with it
  framedata.timestamp

    ...

  // WebVR: Indicates that we are ready to present the rendered frame to the VR display
  vrDisplay.submitFrame();
}

Specifications

Browser compatibility

BCD tables only load in the browser

See also

• WebVR API homepage
• MozVr.com — demos, downloads, and other resources from the Mozilla VR team.