/**
 * Place a DisplayObject3D inside a new DisplayObject3D container, 
 * and align the top-left corner of the do3d to the origin of the container;
 * apply the plane's orignal transformation to the container
 * @param	plane
 * @param	w	width of do3d (or nested plane)
 * @param	h	height of do3d (or nested plane)
 * @return	a DisplayObject3D container with plane as child
 */
private function do3dAlignTL3d(do3d:DisplayObject3D, w:Number, h:Number):DisplayObject3D {
	var cont:DisplayObject3D = new DisplayObject3D();
	cont.x = do3d.x - w/2;  //cont.x = plane.x - w / 2;
	cont.y = do3d.y + h/2; //cont.y = plane.y + h / 2;
	cont.z = do3d.z;
	cont.addChild(do3d);
	do3d.x = w / 2;
	do3d.y = -h / 2;
	do3d.z = 0;
	return cont;
}

/**
 * Place a DisplayObject3D inside a new DisplayObject3D container, 
 * and align the top-center of the do3d to the origin of the container;
 * apply the plane's orignal transformation to the container
 * @param	plane
 * @param	w	width of do3d (or nested plane)
 * @param	h	height of do3d (or nested plane)
 * @return	a DisplayObject3D container with plane as child
 */
private function do3dAlignTC3d(do3d:DisplayObject3D, w:Number, h:Number):DisplayObject3D {
	var cont:DisplayObject3D = new DisplayObject3D();
	cont.x = do3d.x;
	cont.y = do3d.y + h/2;
	cont.z = do3d.z;
	cont.addChild(do3d);
	do3d.y = -h / 2;
	do3d.z = 0;
	return cont;
}

 /**
  *  Transforms (from Normal Flash Coordinate system) a TL2d point to a StaticTL3d point.
  * @param	point in TL2d coord system
  * @return point transformed to TLStatic3d coord system
  */
private function TL2dtoTLStatic3d(point:Point):Point {
	return new Point(point.x, -point.y);
}

 /**
  *  Transforms a TL3d point, to a StaticTL3d point.
  * @param	point in TL3d coord system
  * @return point transformed to TLStatic3d coord system
  */
private function TL3dtoTLStatic3d(point:Point):Point {
	return new Point(point.x + viewport.width / 2, point.y - viewport.height/2 );
}

 /**
  *  Transforms a StaticTL3d point, to a TL3d point.
  * @param	point in StaticTL3d coord system
  * @return point transformed to TL3d coord system
  */
private function TLStatic3dtoTL3d(point:Point):Point {
	return new Point(point.x - viewport.width / 2, point.y + viewport.height/2 );
}

 /**
  *  Transforms a TL2d point, to a TL3d point.
  * @param	point in TL2d coord system
  * @return point transformed to TL3d coord system
  */
private function TL2dtoTL3d(point:Point):Point {
	return new Point(point.x - viewport.width/2, -point.y + viewport.height/2 );
}