| With the intensifying of the information period, the combine of Virtual Reality and GIS technology make it possible to visualize a geographic environment (GE). The research on Digital City, Digital Campus, Digital Earth and Virtual Battlefield has made such a progress that the technology becomes applicable more than theoretical. Three-dimensional model is the basic element of the GE visualization system, and the research on modeling technology has been going with the whole developing process of the GE visualization technology. The key technology of GE modeling and planning will be discussed systematically in this paper.The main work stated in this thesis focuses in the following aspects.1. The Improvement on CSG modeling technique applied to building-modeling. The basic application of the CSG on building-modeling is discussed, and one volume-cell (voxel) growth method is put forward. The using of this modeling method can reduce the load of the voxel set up, and can delete overlapped faces automatically, so that can boost the modeling and the rendering efficiency.2. The construction of road model and the terrain-matching method. Following the transect-based road model, an adaptive road-modeling method based on terrain-matching has been brought forward in this paper. The algorithm gives a better solution of the road-terrain matching problem, and reduces the complexity of road model which can boost the rendering efficiency.3. The technique of terrain-modeling and dynamic terrain-planning. The vector-graph modeling method of DEM and the fractal-construct method of terrain model are discussed. A dynamic terrain planning method based on TM operators is put forward in this paper, which makes it possible to modify terrain at will.4. The design and implementation of GEMS. A Geographic Environment Modeling System is designed and implemented, and the key technology of the planning system is analyzed. At last, this work provides the summarization of the work and the content of the future research. |
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