The Research Of Three-Dimension Urban Modeling Based On Virtual Reality Technology

The constructions and applications of 3D City Model(3DCM) are presently the concemful subjects on the researches of GIS and its related fields.and they are becoming more and more significant for the bulid of "digital earth" and "Cyber city",the constructional method of 3DCM is becoming more and more important. Traditional GIS is a 2D system, It describes 3D objects and theirs phenomenon with points, lines and surfaces in 2D space, which are not accord with people's traditional ideas. Therefore, much more attention were paid on 3DGIS which based on virtual reality technology.Firstly, the paper introduces the basic conception of the digital city, the basic contents and the key technology of the digital city.Secondly, the research status in domestic and overseas is analysed in this paper.The building model's data acquisition,data organization,data management and the model construction method are also discussed in this paper. During the analysis and comparing of existing 3DCM, a divided-box 3D data model which can model a large proportion of simple buildings in urban is brought forward.Data stucture of the model is also put forward. On account of OpenGL can't paint concave polygon, a new method named partition of beenline is brought forward.Based on the model,the author discussed how to realize the visualization of 3DCM. A testing application system named Vritual Reality City Simulation System is developed by the author using Visual C++ and 3D graphic tool OpenGL,which demonstrates the correctness of using this 3DCM to construct regular building.Meanwhile ,in 3D-scene,some functions of spatial analysis and interactive operations have been realized, such as spatial coordinate query, attribute query ,roaming,etc.Finally, the author make a conclusion of the whole thesis and some problems worthy of deeper study are put forward.