PositionSensorVRDevice.getImmediateState() - 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This feature is obsolete.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 getImmediateState() method of the VRDevice interface returns the current instantaneous position sensor state. This is intended to only be used rarely, for certain special uses, for example sampling the immediate position of a hand orientation sensor — or at least it will be, in the future.

For most standard uses, you'll probably want to use PositionSensorVRDevice.getState instead.

Syntax

var myPositionstate = PositionSensorVRDevice.getImmediateState();

Parameters

None.

Returns

A VRPositionState object.

Examples

Our positionsensorvrdevice demo uses the WebVR API to update the view of a simple 2D canvas scene on each frame of a requestAnimationFrame loop. The main function that updates the view data is as follows:

function setView() {
  var posState = gPositionSensor.getImmediateState();
  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 getImmediateState() and storing it in posState (the actual live demo uses getState(), but both seem to do the same thing currently.) 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.