 The following algorithms consider an input that forms a polygon, a polygon with holes, or a PSLG.For a polygonal input we denote the number of vertices by "n" and the number of reflex (concave, i.e., angle greater than ) vertices by "r".If the input is a PSLG then we consider the initial wavefront structure, which forms a set of polygons, and again denote by "n" the number of vertices and by "r" the number of reflex vertices w.r.t.