关键词: 特征约束, 四面体剖分, 地学分析, Delaunay算法

Abstract:

In the modeling process of Virtual Geographic Environment (VGE), as the geological objects generally have characteristics such as complex boundary, many spatial feature constraints including point, line, face and inside hole type, and meanwhile geosciences analysis and calculation require meshes with high quality, it is hard to construct three-dimensional meshes which regard for complex spatial feature constraints of geological objects exactly and have high quality for geosciences analysis and calculation. Aiming at this problem, a constrained Delaunay discrete algorithm of tetrahedral mesh is put forward in this paper. This algorithm first expresses constrained features of complex geological objects as a series of constraint points, constraint segments and constraint faces in Piecewise Linear Complexes (PLC), and then implements the initial Delaunay tetrahedral subdivision from the initial point set of the geological objects Piecewise Linear Complexes by using the Bowyer-Watson algorithm. Following the upper steps, the algorithm recovers the lost constraint lines and the lost constraint faces in sequence through adding some extra vertices during the mesh discrete process and it should guarantee the adding vertices do not encroach other constraint lines or constraint faces. The constraint face recovery is after the constraint line recovery and it is more difficult and complex than the constraint line recovery. In this step, some local meshes are demanded to reconstruct and must conform to the Delaunay empty circumsphere criterion. And then, the object model external tetrahedron elements should be deleted by adopting a marking method. After this step, it performs the mesh quality control process by restricting the maximum radius-distance ratio or the volume of tetrahedron element in the mesh. In this step, some extra vertices are also added in the tetrahedron elements which can not satisfy the user restricting quality. It is proved that the algorithm can produce meshes not only satisfying different constrained criteria but also with high quality for geosciences analysis and calculation.

Key words: geosciences analysis, feature constrainted, tetrahedralization, Delaunay