The getViewerPose() method, a member of the XRFrame interface, returns a XRViewerPose object which describes the viewer's pose (position and orientation) relative to the specified reference space.

See the getPose() method for a way to calculate a pose that represents the difference between two spaces.

referenceSpace

An XRReferenceSpace object specifying the space to use as the reference point or base for the computation of the viewer's current pose.

A XRViewerPose describing the viewer's position and orientation relative to the specified reference space.

InvalidStateError DOMException

Thrown if getViewerPose() was not called within the context of a callback to a session's XRSession.requestAnimationFrame().

In this callback function for requestAnimationFrame(), the XRViewerPose describing the viewer's viewpoint on the world is obtained by calling getViewerPose() on the XRFrame passed into the callback.

viewerPose = xrFrame.getViewerPose(xrReferenceSpace);

if (viewerPose) {
  /* render the pose's views */
}

To see a complete example, take a look at Movement, orientation, and motion.