code: function(point) {
                  if (!this.contains(point)) { return null; }
                  var P = point.elements || point;
                  var A = this.anchor.elements, D = this.direction.elements;
                  return (P[0] - A[0]) * D[0] + (P[1] - A[1]) * D[1] + ((P[2] || 0) - A[2]) * D[2];
                }
docs: Returns the distance from the anchor of the given point. Negative values are returned for points that are in the opposite direction to the line's direction from the line's anchor point.