TP [0054] where r denotes a vector of any point along the line, r ^ TP = r ??? TP ??? r ??? TP ??? [0055] rTP denotes a vector from the target point T to the pivot point P, and k is a parameter that measures the distance along the line from the target point ???T???. [0056] In the frame of Cartesian coordinates, a plane can be generally defined as ??x+??y+??z=1 [0057] where ?????? are three paramet