1. A method for processing in a data processing system whether a planar object in a three dimensional space intersects a three dimensional picking volume comprising the steps of: a) displaying the planar object on a display; b) first calculating in a processor whether a plane containing the displayed object in the three dimensional space intersects an edge of the three dimensional picking volume; c) subsequently calculating in the processor whether the displayed object and the picking volume intersect when the object is determined to intersect the edge of the picking volume previously calculated to intersect the plane containing the displayed object; and d) displaying an indication whether the displayed object intersects the picking volume.