VRPositionState

The VRPositionState interface of the WebVR API represents the position state at a given timestamp (which includes orientation, position, velocity, and acceleration information.)

This interface is accessible through the PositionSensorVRDevice.getState() method.

Properties

VRPositionState.timeStamp Read only

Returns the current time stamp of the system — a monotonically increasing value useful for determining if position data has been updated, and what order updates have occured in.

VRPositionState.hasPosition Read only

A boolean indicating whether the VRPositionState.position property is valid (i.e. if the hardware is currently registering a valid position). If it is false, the position property will return null.

VRPositionState.position Read only

Returns the current position of the sensor relative to the head mounted display, as a 3D vector (DOMPoint value.)

VRPositionState.linearVelocity Read only

Returns the current linear velocity of the sensor.

VRPositionState.linearAcceleration Read only

Returns the current linear acceleration of the sensor.

VRPositionState.hasOrientation Read only

A boolean indicating whether the VRPositionState.orientation property is valid (i.e. if the hardware is currently registering a valid orientation). If it is false, the orientation property will return null.

VRPositionState.orientation Read only

Returns the current orientation of the sensor relative to the head mounted display, as a quarternion value (currently represented by a DOMPoint value, but will be updated when DOMQuarternion is implemented.)

VRPositionState.angularVelocity Read only

Returns the current angular velocity of the sensor.

VRPositionState.angularAcceleration Read only

Returns the current angular acceleration of the sensor.

Examples

The following example is taken from our positionsensorvrdevice demo, which uses the WebVR API to update the view of a simple 2D canvas scene on each frame of a requestAnimationFrame loop.

function setView() {
  var posState = gPositionSensor.getState();
  if(posState.hasPosition) {
    posPara.textContent = 'Position: x' + roundToTwo(posState.position.x) + " y"
                                + roundToTwo(posState.position.y) + " z"
                                + roundToTwo(posState.position.z);
    xPos = -posState.position.x * WIDTH * 2;
    yPos = posState.position.y * HEIGHT * 2;
    if(-posState.position.z > 0.01) {
      zPos = -posState.position.z;
    } else {
      zPos = 0.01;
    }
  }

  if(posState.hasOrientation) {
    orientPara.textContent = 'Orientation: x' + roundToTwo(posState.orientation.x) + " y"
                                + roundToTwo(posState.orientation.y) + " z"
                                + roundToTwo(posState.orientation.z);
    xOrient = posState.orientation.x * WIDTH;
    yOrient = -posState.orientation.y * HEIGHT * 2;
    zOrient = posState.orientation.z * 180;

  }
}

Here we are grabbing a VRPositionState object using PositionSensorVRDevice.getState() and storing it in posState. We then check to make sure that position and orientation info is present in the current frame using VRPositionState.hasPosition and VRPositionState.hasOrientation (these return null if, for example the head mounted display is turned off or not pointing at the position sensor, which would cause an error.)

We then output the x, y and z position and orientation values for informational purposes, and use those values to update the xPos, yPos, and zPos variables, which are used to update the scene rendering on each frame.

Specifications

Browser compatibility

• [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

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