code: function(line2d) {
              var point = CSG.solve2Linear(this.normal.x, this.normal.y, line2d.normal.x, line2d.normal.y, this.w, line2d.w);
              point = new CSG.Vector2D(point); // make  vector2d
              return point;
          }
docs: /*FIXME: has error - origin is not defined, the method is never used
  closestPoint: function(point) {
  point = new CSG.Vector2D(point);
  var vector = point.dot(this.direction());
  return origin.plus(vector);
  },
   intersection between two lines, returns point as Vector2D