Study On Simplification Arithmetic Of 3D Building

During the past decades, automatic cartography generalization is always a great challenge to the entire world's cartographers. With the development of cartography related technology and introduction of 3D visualization, 3D city becomes an important research major in field of cartography because of its directness and vitality. Building is one of the most important parts in 3D city, so the study of 3D building generalization is of great importance to 3D city modeling and visualization.Generalization of 3D building is a complex project, including different methods for many kinds of buildings under the given requirements. The study on this major is on its initial phase, there's little experience to be use for reference. The paper started with the relationship between the modeling of 3D city and LOD of 3D buildings and simplification arithmetic of 3D buildings are studied in detail, the main works and creations are as follows:(1) Beginning with the description of 3D building and the acquisition of building model, the characteristic of 3D building generalization is summarized.(2) The general methods of 3D building generalization are discussed and issues related to 3D building model's LOD are studied.(3) Two different kinds of data structures for 3D building model are proposed for different uses.(4) Based on the arithmetic of facet moving, taking the shortest distance and the minimum character into account, simplification of parallel building is realized. The two methods are analyzed and contrasted in detail in three aspects as generalization course, generalization results and uncertainty. In realization of facet moving, triangulation arithmetic is brought forward, which can divide all kinds of planar polygon. Based on the Delaunay triangulation, the arithmetic works efficiently and preferably and its application can also be extend to other fields.(5) An initial study has been done with the simplification of the inclined roof and special building. Expressing the inclined roof of buildings geometrically, topology and semantic information are established and a method with squaring inclined facets group and processing unattached inclined facet combined is developed to simplify the inclined roof. In the simplification of special 3D building, combining with the characters of 3D building, a simplification method of special building has been brought forward based on shape recognition.