VRPose.position - Web APIs 编辑

Experimental

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

The position read-only property of the VRPose interface returns the position of the VRDisplay at the current VRPose.timestamp as a 3D vector.

The coordinate system is as follows:

• Positive X is to the user’s right.
• Positive Y is up.
• Positive Z is behind the user.

Positions are measured in meters from an origin point — this point is either the position the sensor was first read at, or the position of the sensor at the point that VRDisplay.resetPose() was last called.

Note: By default, all positions are given as a sitting space position. Transforming this point with VRStageParameters.sittingToStandingTransform — when you are working with a room display for example — converts this to a standing space position.

Syntax

var myPosition = VRPose.position;

Value

A Float32Array, or null if the VR sensor is not able to provide position data.

Note: User agents may provide emulated position values through techniques such as neck modeling; when doing so they should still report VRDisplayCapabilities.hasPosition as false.

Examples

var frameData = new VRFrameData();
var vrDisplay;

navigator.getVRDisplays().then(function(displays) {
  vrDisplay = displays[0];
  console.log('Display found');
  // Starting the presentation when the button is clicked: It can only be called in response to a user gesture
  btn.addEventListener('click', function() {
    vrDisplay.requestPresent([{ source: canvas }]).then(function() {
      drawVRScene();
    });
  });
});

// WebVR: Draw the scene for the WebVR display.
function drawVRScene() {
  // WebVR: Request the next frame of the animation
  vrSceneFrame = vrDisplay.requestAnimationFrame(drawVRScene);

  // Populate frameData with the data of the next frame to display
  vrDisplay.getFrameData(frameData);

  // You can get the position, orientation, etc. of the display from the current frame's pose
  // curFramePose is a VRPose object
  var curFramePose = frameData.pose;
  var curPos = curFramePose.position;
  var curOrient = curFramePose.orientation;

  // Clear the canvas before we start drawing on it.

  gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

  // WebVR: Create the required projection and view matrix locations needed
  // for passing into the uniformMatrix4fv methods below

  var projectionMatrixLocation = gl.getUniformLocation(shaderProgram, "projMatrix");
  var viewMatrixLocation = gl.getUniformLocation(shaderProgram, "viewMatrix");

  // WebVR: Render the left eye’s view to the left half of the canvas
  gl.viewport(0, 0, canvas.width * 0.5, canvas.height);
  gl.uniformMatrix4fv(projectionMatrixLocation, false, frameData.leftProjectionMatrix);
  gl.uniformMatrix4fv(viewMatrixLocation, false, frameData.leftViewMatrix);
  drawGeometry();

  // WebVR: Render the right eye’s view to the right half of the canvas
  gl.viewport(canvas.width * 0.5, 0, canvas.width * 0.5, canvas.height);
  gl.uniformMatrix4fv(projectionMatrixLocation, false, frameData.rightProjectionMatrix);
  gl.uniformMatrix4fv(viewMatrixLocation, false, frameData.rightViewMatrix);
  drawGeometry();

  function drawGeometry() {
    // draw the view for each eye
  }

    ...

  // WebVR: Indicate that we are ready to present the rendered frame to the VR display
  vrDisplay.submitFrame();
}

Note: You can see this complete code at raw-webgl-example.

Specifications

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.