面向地表上、下集成的二维/三维单纯形剖分算法实验

对地上实体、地形表面和地下实体的集成建模是国内外研究的热点。本文以单纯复形理论,提出了一种以约束Delaunay三角网为纽带,用边界表示模型-不规则三角网-四面体格网的集成空间数据模型,对地上实体、地表和地下空间对象进行无缝集成。用边界表示模型表达地面上复杂的对象,用不规则三角网表达地形,用四面体格网表示地质体对象。对传统的逐点插入法构建约束Delaunay三角网算法进行改进,生成约束Delaunay三角网,对地上实体和地表进行集成。其对不同的地层数据分别进行Delaunay三角剖分,构成四面体剖分的上下边界,构建上、下地层之间的侧边界,形成空腔,进而对空腔进行四面体剖分,形成分层表达的地质体对象。同时设计了一个原型系统,对算法进行验证,展示了其实验结果。

Study on 2D/3D Simplex-based Partition Algorithms for Aboveground,Ground and Underground Objects

The seamless integration of the aboveground,ground and underground objects is the research focus at home and abroad.Taking CD-TIN as a link and B-Rep-TIN-TEN as core data model,a new method is proposed for the integration of the aboveground,ground and underground objects based on the simplex theory in point set topology.The well-known B-Rep is used to represent complex above ground objects.Terrain is modeled by TIN,and geologic object is represented by TEN.An improved incremental insertion point method is proposed.In contrast with the traditional incremental insertion point method,this algorithm enhances time efficiency largely.The comparison result is listed in this paper.CD-TIN is constructed to integrate terrain points and aboveground entities which are represented by B-Rep model.Firstly,the boundary of above ground objects,which are taken as the constraint,is calculated.Secondly,the terrain points are constructed to form TIN.Then,the constraint elements are added to rebuild TIN.CD-TIN construction process includes three steps： the search of the constraint region,the triangulation of the polygon,and an overall Delaunay triangulation of the TIN based on the ＂half-separated additional characteristic point inserting technique＂ method by adding virtual point on the constraint line.The stratums are partitioned by CD-TIN firstly and the adjacent stratums form the top boundary and bottom boundary.Moreover,the side boundaries are also constructed to form the empty cell in the 3D space.The empty cell is the partition space of TEN.This can ensure TEN are in the empty cell and don＇t over the boundary.And,the empty cell is partitioned by TEN.At last,a prototype is implemented and developed under the Visual Studio.NET 2008 development environment combined with OpenGL technology to testify the algorithms,and the results are showed.The seamless integration of buildings,terrain and geology are implemented.