Boundary Conforming Discretization
of Three-Dimensional Domains
Daniel Rypl, Zdeněk Bittnar
Department of Mechanics
Faculty of Civil Engineering
Czech Technical University in Prague
Thákurova 7, 166 29 Prague, Czech Republic
Abstract:
In this paper, an algorithm for the discretization of 3D
domains into tetrahedral boundary conforming meshes is presented.
The algorithm is based on the Delaunay triangulation with special
point ordering. The conformity of the resulting mesh with the initial
triangulation of the domain boundary is ensured a priori thus the
boundary recovery postprocessing step is eliminated. The constrained
Delaunay triangulation of the boundary points is obtained using modified
Watson's point insertion algorithm. The actual appearance of boundary
faces in the final triangulation is achieved by proper ordering of
point insertion that is driven by the dependency, represented in the
form of an oriented graph, of the violation of the empty-sphere property
of all boundary faces. The cyclic dependencies (closed loops in the
graph) are eliminated by using the nodal perturbations, by
classification of some of the violations as safe and (as
the last resort) by forming a new tetrahedron using the advancing
front technique. Once all the cyclic dependencies are eliminated, the
point insertion process controlled by the dependency graph is started
and the constrained Delaunay triangulation of the boundary points is
built. In the next phase, additional points are inserted in the
interior of the domain, while preserving the boundary
constraints, to make the elements of appropriate size with aspect ratio
close to one. The resulting mesh is then subjected to optimization in
terms of the combination of Laplacian smoothing and topological
transformations, in order to remove the potential slivers and to
improve the overall mesh quality.