Research On The Fusion Method Of3-dimentional Feature Models And Multi-scale Terrain

Geographical environment is a complex and vast ecosystem, including not only the undulating terrain, also a variety of surface features.In the process of showing the geographical environment factors, three dimensional visualization of geographic information technology was divided into three-dimensional terrain visualization and three-dimensional visualization of surface features depending on the visual objects.With the deepening of the three-dimensional visualization applications, the demand for realism and fidelity of the geographical environment is also increasing. The vivid display of high-precision topography and surface features has become the key of virtual geographic environment simulation. The method and theory of seamless integration between terrain and surface features in virtual geographic environment has become in-depth exploration and research questions in the field of3D GIS.With a review of the fusion method of three dimensional feature object and the terrain, the visualization of the three dimensional terrain, and the fusion with the feature object were analyzed and studied in this paper. And the emphases were taken on two main aspects:the technology of terrain modeling and loading, and the method of simplify of three dimensional feature models. Meanwhile, based on the geometric way, a further research of the seamless fusion method of terrain and the feature models were carried out. Finally, a system for the fusion of the three dimensional terrain and feature models were designed and completed, which based on the technology of OpenSceneraph and the terrain processing technology of VirtualPlanet Builder.The details can be described as follows:(1) Research on home and abroad advances of topics. Firstly, the background was introduced, the overseas and domestic research status of the fusion method of the three dimensional feature models with the terrain were analyzed.And the same as the purpose, the meaning, the supporting technologies and the main contents.(2) Research on three-dimensional terrain modeling techniques based on multi-resolution pyramid technology. After analysis and comparison of the advantages and shortcomings of the representation ways of digital terrain, a special way was designed, which was based on the grid terrain model, and do a triangularization for it, to build a massive terrain data. Then a futher research on building multi-resolution pyramid model for multi-scale terrain based on multi-resolution LOD. Finally, based on the dynamic scheduling technology, studied the organization of the three dimensional terrain model and multi-resolution texture mapping technology, so as to realize the rapid visualization of3D terrain scene.(3) Research on the fusion of three-dimension terrain and surface features geometry-based approach. Firstly, the modeling and simplified method of the three dimensional feature which linked with the terrain model were took as the second emphasis. The method contains the point features interpolation and matching to the terrain model, the linear features and the polygon features matching to the terrain models which depend on its characteristics of vector data, building the constraint boundary, and realizes the seamless fusion of the features with the terrain geometry-based approach at last.(4) The design and implementation for the experimental system was completed at the end.