Revision 970951 of VRPose

<div>{{APIRef("WebVR API")}}{{SeeCompatTable}}</div>

<p>The <strong><code>VRPositionState</code></strong> interface of the <a href="/en-US/docs/Web/API/WebVR_API">WebVR API</a> represents the position state at a given timestamp (which includes orientation, position, velocity, and acceleration information.)</p>

<p>This interface is accessible through the {{domxref("PositionSensorVRDevice.getState()")}} method.</p>

<h2 id="Properties">Properties</h2>

<dl>
 <dt>{{domxref("VRPositionState.timeStamp")}} {{readonlyInline}}</dt>
 <dd>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.</dd>
 <dt>{{domxref("VRPositionState.hasPosition")}} {{readonlyInline}}</dt>
 <dd>A boolean indicating whether the {{domxref("VRPositionState.position")}} property is valid (i.e. if the hardware is currently registering a valid position). If it is <code>false</code>, the position property will return <code>null</code>.</dd>
 <dt>{{domxref("VRPositionState.position")}} {{readonlyInline}}</dt>
 <dd>Returns the current position of the sensor relative to the head mounted display, as a 3D vector ({{domxref("DOMPoint")}} value.)</dd>
 <dt>{{domxref("VRPositionState.linearVelocity")}} {{readonlyInline}}</dt>
 <dd>Returns the current linear velocity of the sensor.</dd>
 <dt>{{domxref("VRPositionState.linearAcceleration")}} {{readonlyInline}}</dt>
 <dd>Returns the current linear acceleration of the sensor.</dd>
 <dt>{{domxref("VRPositionState.hasOrientation")}} {{readonlyInline}}</dt>
 <dd>A boolean indicating whether the {{domxref("VRPositionState.orientation")}} property is valid (i.e. if the hardware is currently registering a valid orientation). If it is <code>false</code>, the orientation property will return <code>null</code>.</dd>
 <dt>{{domxref("VRPositionState.orientation")}} {{readonlyInline}}</dt>
 <dd>Returns the current orientation of the sensor relative to the head mounted display, as a quarternion value (currently represented by a {{domxref("DOMPoint")}} value, but will be updated when <code>DOMQuarternion</code> is implemented.)</dd>
 <dt>{{domxref("VRPositionState.angularVelocity")}} {{readonlyInline}}</dt>
 <dd>Returns the current angular velocity of the sensor.</dd>
 <dt>{{domxref("VRPositionState.angularAcceleration")}} {{readonlyInline}}</dt>
 <dd>Returns the current angular acceleration of the sensor.</dd>
</dl>

<h2 id="Examples">Examples</h2>

<p>The following example is taken from our <a href="https://mdn.github.io/webvr-tests/positionsensorvrdevice/">positionsensorvrdevice</a> demo, which uses the WebVR API to update the view of a simple {{domxref("CanvasRenderingContext2D","2D canvas")}} scene on each frame of a {{domxref("window.requestAnimationFrame()","requestAnimationFrame")}} loop.</p>

<pre class="brush: js">
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 &gt; 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;

  }
}</pre>

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

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

<h2 id="Specifications">Specifications</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
  <tr>
   <td>{{SpecName('WebVR', '#vrpositionstate', 'VRPositionState')}}</td>
   <td>{{Spec2('WebVR')}}</td>
   <td>Initial definition</td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_compatibility">Browser compatibility</h2>

<p>{{CompatibilityTable}}</p>

<div id="compat-desktop">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Chrome</th>
   <th>Firefox (Gecko)</th>
   <th>Internet Explorer</th>
   <th>Opera</th>
   <th>Safari (WebKit)</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatVersionUnknown}}<sup>[1]</sup></td>
   <td>{{CompatGeckoDesktop(39)}}<sup>[2]</sup></td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
  </tr>
 </tbody>
</table>
</div>

<div id="compat-mobile">
<table class="compat-table">
 <tbody>
  <tr>
   <th>Feature</th>
   <th>Android</th>
   <th>Firefox Mobile (Gecko)</th>
   <th>Firefox OS (Gecko)</th>
   <th>IE Phone</th>
   <th>Opera Mobile</th>
   <th>Safari Mobile</th>
   <th>Chrome for Android</th>
  </tr>
  <tr>
   <td>Basic support</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatGeckoMobile(39)}}<sup>[2]</sup><br />
    {{CompatGeckoMobile(44)}}<sup>[3]</sup></td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
   <td>{{CompatNo}}</td>
  </tr>
 </tbody>
</table>
</div>

<ul>
 <li>[1] The support in Chrome is currently experimental. To find information on Chrome's WebVR implementation status including supporting builds, check out <a href="https://blog.tojicode.com/2014/07/bringing-vr-to-chrome.html">Bringing VR to Chrome</a> by Brandon Jones.</li>
 <li>[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 <code>about:config</code> and enable the <code>dom.vr*</code> prefs. A better option however is to install the <a href="https://www.mozvr.com/downloads/webvr-addon-0.1.0.xpi">WebVR Enabler Add-on</a>, which does this for you and sets up other necessary parts of the <a href="/en-US/docs/Web/API/WebVR_API/WebVR_environment_setup">environment</a>.</li>
 <li>[3] The <code>dom.vr*</code> prefs are enabled by default at this point, in Nightly/Aurora editions.</li>
</ul>

<h2 id="See_also">See also</h2>

<ul>
 <li><a href="/en-US/docs/Web/API/WebVR_API">WebVR API homepage</a>.</li>
 <li><a href="https://mozvr.com/">MozVr.com</a> — demos, downloads, and other resources from the Mozilla VR team.</li>
</ul>