VRPositionState.linearVelocity

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 linearVelocity read-only property of the VRPositionState interface returns the current linear velocity of the sensor.

This is the current velocity at which the sensor is moving, along the x, y, and z axes. If the sensor is incapable of providing linear velocity, the method will return null.

Syntax

var myLinearVelocity = VRPositionState.linearVelocity;

Value

A DOMPoint.

Examples

The following example is taken from our velocity-acceleration demo, which uses the WebVR API to update the view of a simple 2D canvas scene on each frame of a requestAnimationFrame loop, while ouputting the linearVelocity, VRPositionState.linearAcceleration, VRPositionState.angularVelocity, and VRPositionState.angularAcceleration values to the UI on each frame for information purposes.

function setView() {
  var posState = gPositionSensor.getState();
  
    ...

  linVelPara.textContent = 'Linear velocity: x' + formatNumber(posState.linearVelocity.x) + " y"
                                + formatNumber(posState.linearVelocity.y) + " z"
                                + formatNumber(posState.linearVelocity.z);

  linAccPara.textContent = 'Linear acceleration: x' + formatNumber(posState.linearAcceleration.x) + " y"
                                + formatNumber(posState.linearAcceleration.y) + " z"
                                + formatNumber(posState.linearAcceleration.z);
 
  angVelPara.textContent = 'Angular velocity: x' + formatNumber(posState.angularVelocity.x) + " y"
                                + formatNumber(posState.angularVelocity.y) + " z"
                                + formatNumber(posState.angularVelocity.z);

  angAccPara.textContent = 'Angular acceleration: x' + formatNumber(posState.angularVelocity.x) + " y"
                                + formatNumber(posState.angularVelocity.y) + " z"
                                + formatNumber(posState.angularVelocity.z);
}

function formatNumber(number) {
  number = number.toFixed(2);
  if(number => 0) {
    number = Math.abs(number);
    number = number.toFixed(2);
    number = "+" + number;
  }
  return number;
}

This allows you to get an idea of how these values change as the VR headset is moved and rotated.

Specifications

Specification Status Comment
WebVR
The definition of 'linearVelocity' in that specification.
Editor's Draft Initial definition

Browser compatibility

Feature Chrome Firefox (Gecko) Internet Explorer Opera Safari (WebKit)
Basic support (Yes)[1] 39 (39)[2] No support No support No support
Feature Android Firefox Mobile (Gecko) Firefox OS (Gecko) IE Phone Opera Mobile Safari Mobile Chrome for Android
Basic support No support 39.0 (39)[2]
44.0 (44)[3]
No support No support No support No support No support
  • [1] The support in Chrome is currently experimental. To find information on Chrome's WebVR implementation status including supporting builds, check out Bringing VR to Chrome by Brandon Jones.
  • [2] The support for this feature is currently disabled by default in Firefox. To enable WebVR support in Firefox Nightly/Developer Edition, you can go to about:config and enable the dom.vr* prefs. A better option however is to install the WebVR Enabler Add-on, which does this for you and sets up other necessary parts of the environment.
  • [3] The dom.vr* prefs are enabled by default at this point, in Nightly/Aurora editions.

See also

Document Tags and Contributors

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