Away3DLite: 3D Coordinates to 2D Coordinates

這個在寫 3D Application 時常用的技巧
要計算出 3D Object 在 screen 的 2D position. 

Away3DLite 的寫法:

public function calc2DCoords(screen_element:*):Point
{

    var posn:Vector3D = screen_element.viewMatrix3D.position;
    var screenX:Number = posn.x / posn.z;
    var screenY:Number = posn.y / posn.z;

    return new Point(screenX+screenW_offset,screenY+screeH_offset);
}

如果有 Away3D 就可以直接用 camera.screen function.