PositionSensorVRDevice.getState() - Web APIs 编辑

Obsolete

This feature is obsolete. Although it may still work in some browsers, its use is discouraged since it could be removed at any time. Try to avoid using it.

Experimental

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

The getState() method of the PositionSensorVRDevice interface returns the current state of the position sensor for the current frame (e.g. within the current window.requestAnimationFrame callback) or for the previous frame, contained with a VRPositionState object. This is the method you'd normally want to use, vs. PositionSensorVRDevice.getImmediateState.

Syntax

var myPositionState = PositionSensorVRDevice.getState();

Parameters

None.

Returns

A VRPositionState object.

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 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, zPos,xOrient, yOrient, and zOrient variables, which are used to update the scene rendering on each frame.

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.