/** Add a point, specified by its position and normal, to the point cloud. */
 void addPoint(Vector3 const & p, Vector3 const & n) { points.push_back(Point(p, n)); bbox.merge(p); }
 /** Add a point to the point cloud. */
 void addPoint(Point const & p) { points.push_back(p); bbox.merge(p.getPosition()); }