Geometry Simplification For Buildings In Virtual City

Virtual city is usually based on the detail and huge-sized geometric models. These models, often represented as complex triangle meshes. It costs much and takes times to build virtual cities and it also takes much time to visualize in real time. To reduce the rendering time the geometric models are usually managed in the LOD (level-of-detail) strategy. The traditional method is to set up different LOD models by hand. This kind of method has kept a lot of copies of the primitive model; each copy corresponds to a certain models of specific resolution. It cost much time to load these geometric models, and it will present the popping on the vision when switch over among different LOD models. Our suggested method in this paper uses the opposite approach to that of virtual city. It based on the mesh simplification for constructing a progressive mesh representation from an arbitrary mesh. Thus the data are kept as compact as possible and then the data building time in addition to the loading time is reduced significantly. This paper proposed a novel edge-collapse based LOD algorithm to simplify the geometric models of architecture and simultaneously preserve the characteristic edge. Our method makes pre-simplified progressive mesh as a function of normal and edge-energy. We collapse the edges with closed normals in order to keep the characteristic planes, and collapse the edges by the control of edge-energy.