• DirectedDistance1[cnum, point1, point2, vector, dist] constrains point1 to lie dist units away from point2, measured in the direction of vector.
• DirectedDistance1[cnum, point1, point2, vector] uses the magnitude of vector for the distance specification.
• DirectedDistance1 constrains one degree of freedom.
• If point2 is omitted, it is assumed to be the global origin.
• See also: DirectedPosition2, PointOnLine1, PointOnPlane1, SetConstraints, SysCon.