The Research On Key Technologies Of 4D Virtual City System

Four-dimensional world is the real world; everything has the character of time. The traditional virtual city systems only show the city scene of some given time, without relating its history and future. If adding the time dimension to the traditional three-dimensional virtual city system, it will become the 4D (four-dimensional) virtual city system. The 4D virtual city system can display the city scene in time process, can show the city of history, nowadays and future, it will become an important tool to help layout research, report, display and assist decision-making。This paper first discusses the basis theory of urban-simulation, including its concept, research system and its key technologies. At the same time, the paper gives the concept and function of 4D virtual city. Then the paper discusses the theory and design method of spatio-temporal database, analyzes the exist spatio-temporal data models in GIS field, compares their advantages and disadvantages. In view of the characteristics and the requirements of urban-simulation, the paper advances a spatio-temporal database manage model based on the expanding update spatio-temporal data model, using historical sub-database, present state sub-database and flow-database to manage the multi-source datas. The other key technology of city-scene modeling is discussed, including city scenes of the terrain, buildings, trees, using the modeling software of MultiGen Creator to implement. Also the technology of integrating culture feature and terrain is studied.Integrating the spatio-temporal database manage model and the scene modeling technique, this paper constructs the 4D virtual city system of FoShan on the basis of design principles for framework and function modules. The simulation result agrees well with desire. The end of the paper suggests that advanced researches are needed to be done.