// compute a start point in 3D view
boost::shared_ptr<GeomDataAPI_Point2D> aStartAttr =
boost::dynamic_pointer_cast<GeomDataAPI_Point2D>(data()->attribute(LINE_ATTR_START));
// compute a start point in 3D view
boost::shared_ptr<GeomDataAPI_Point2D> aStartAttr =
boost::dynamic_pointer_cast<GeomDataAPI_Point2D>(data()->attribute(LINE_ATTR_START));