code: function(obj) {
                  if (obj.normal) { return null; }
                  if (obj.direction) {
                    return (this.contains(obj.anchor) && this.contains(obj.anchor.add(obj.direction)));
                  } else {
                    var P = obj.elements || obj;
                    var A = this.anchor.elements, N = this.normal.elements;
                    var diff = Math.abs(N[0]*(A[0] - P[0]) + N[1]*(A[1] - P[1]) + N[2]*(A[2] - (P[2] || 0)));
                    return (diff <= sylvester.precision);
                  }
                }
docs: Returns true iff the plane contains the given point or line