Research On 3D Terrain Modeling Technology Based On Discrete Data

Three-dimensional (3D) terrain visualization is always a hot topic in Geographic Information System (GIS), Virtual Reality (VR), Computer Graphics and other related fields. According to the current research situation of 3D terrain modeling and visualization technology, this thesis focuses on discussion and research of the key modeling technology , digital terrain modeling, terrain model simplification and construction of multi-resolution modeling. The thesis aimed to construct digital terrain modeling by discrete data, and to realize the simulation of 3D terrain surface. The main research results are summarized as follows.(1) DEM data acquisition method and terrain surface modeling method are researched in the construction of digital terrain model by discrete data.(2) On the basis of common Delaunay triangulation algorithm analysis, to solve the existing problems of low speed that triangle network building with large scale discrete data, an improved algorithm is presented in this thesis. First, discrete points are adaptively divided into many sub-blocks, then the discrete points in each sub-block are triangulated, fnally all of the sub- triangulation network are incorporated into together, in order to construct triangulation model that covers the whole area.(3)When these complex models are dealt with by computer, there are many difficulties such as display, rendering, storage and so on. In order to solve these problems, this thesis presented an algorithm of simplification for terrain model based on progressive meshes. The calculation methods of priority of edge and importance degree of point are provided in the improvement algorithm by real terrain feature, the algorithm determines the priority level on each edge and delete some less important degree point in the terrain triangular mesh, to realize the simplified terrain model.(4) According to the position of viewpoint,the terrain multi-resolution model based on the TIN is constructed in this thesis. Finally, based on research above, combining with Clipping Algorithm of visual areas and arbitrary direction roaming method, this thesis realized the 3D terrain modeling and real-time simulation of terrain based on discrete data.