Shape-preserving meshes and generalized Morse-Smale complexes
Feng Wei Sun · 2011
Discrete representation of a surface, especially the triangle mesh, is ubiquitous in numerical simulation and computer graphics. Compared with isotropic triangle meshes, anisotropic triangle meshes provide more accurate results in numerical simulation by capturing anisotropic features more faithfully. Furthermore, emerging applications in computer graphics and geometric modeling require reliable differential geometry information estimated on these anisotropic meshes. The first part of this thesis proposes a special type of anisotropic meshes, called shape-preserving meshes, provides guaranteed convergence of discrete differential operators on these meshes and devises an algorithm for generating shape-preserving meshes on free-form surfaces based on the mesh optimization framework with centroidal Voronoi tessellation (CVT). To improve the numerical stability in simulation, we discuss how to reduce the number of obtuse triangles in the mesh. The second part of the thesis discusses the non-uniqueness of anisotropic meshes to represent the same anisotropy defined on a domain, shows that of all anisotropic meshes, there exists one instance minimizing the number of obtuse triangles, and proposes a variational approach to suppressing obtuse triangles in anisotropic meshes by introducing a Minkowski metric in the CVT framework. On a complex shape, its topological information is also highly useful to guide the mesh generation. To extract topology properties, the Morse-Smale complex (MSC) is a classical tool and widely used in computer graphics. However, on a manifold with boundary, its MSC is not well defined. The final part of this thesis generalizes the MSC to manifolds with boundaries. Based on this generalized MSC (GMSC), an operator to merge n GMSCs of manifolds partitioning a large manifold is proposed. The merging operator is used in a divide-and-conquer approach on a massive data set, providing the potential to employ the computational power in a parallel manner.