getProjectedPosition(x, y, z) {
    this.updateMatrices()
    notifyWorldGetter.value = null
    notifyWorldGetter.worldPosition = singletonVec3.set(x || 0, y || 0, z || 0).applyMatrix4(this.threeObject.matrixWorld)
    this.notifyWorld('projectWorldPosition', notifyWorldGetter)
    return notifyWorldGetter.value
  }
Get the current projected user space position for this object, or for a specific position
in its object space.
@returns {Vector3} x and y are in screen pixels, z is worldspace distance from camera. The
                   z may be negative, which means it is out of view behind the camera.