Delaunay conforming triangulations are recommended over constrained triangulations. Special cases of PSLGs are triangulations (polygon triangulation, point set triangulation). For some graphs, such as Delaunay triangulations, both metric and topological properties are of importance. The homeomorphisms can be chosen to be piecewise linear on corresponding triangulations. A very efficient algorithm for parallel Delaunay triangulations appears in Blelloch et al. Maximal outerplanar graphs are also formed as the graphs of polygon triangulations. Approaches that use this method include causal dynamical triangulations and spinfoam models. Flip graphs may also be defined using combinatorial objects other than triangulations. A particularly interesting kind of triangulations are the Delaunay triangulations. "n"-manifolds have triangulations that are inequivalent. Some authors require that all the points of formula 1 are vertices of its triangulations. The two ears theorem is equivalent to the existence of polygon triangulations. Examples include the study of sphere packings, triangulations, the Kneser-Poulsen conjecture, etc. The 1-skeletons of Whitney triangulations are exactly the locally cyclic graphs other than "K". This image illustrates possible triangulations of a regular hexagon.