Building Model Based On CSG In Digital City

3D city model is a important aspect of UGIS and an important part of Digital Earth which aroused GIS academe and application department concern widely.Building practicality model of city spatial objects is a key question which should be solved in 3D UGIS. On the basis of analysis of digital city research framework and existing 3D urban model, this paper researches mainly the techniques of building model based on CSG in digital city. First, the paper summarizes a group building CSG entity and makes combination mode of CSG entities clear, by abstracting building model and analyzing building graphic objects. Depending on this model, the article describes topology relations of the 3D architecture model inner based on the point, line, surface and entity. Finally, in the developing environment VC++, based on the OpenGL techniques, 3D building model of TYUT office building is implemented by CSG .