.3 D Gis In Three-dimensional Topography Simulation With Trees Solid Modeling

Since the Geographical Information System (CIS) came out, there have been a lot of satisfactory productions. The research about 3D GIS based on real three dimention space is a big flight on the development of GIS domain. The research contents of 3D GIS include three dimention visualization, three dimention space database management and three dimention space analysis. There hasn't any successful production of 3D GIS from now on because of the research beening done. This article put focus on the technology of three dimention visualization in 3D GIS including the three dimention terrain simulation and the treesimulation method, in order to make some useful research for building three dimention geographical scene with real visual effect in 3D GIS.The terrain surface is the start point of three dimention visualization research in 3D GIS, because of its important and basal function in 3D GIS. So the terrain surface fitting based on discrete data is one of the important research in this article. The article build the mathematic model of terrain surface with the nonlinear insert calculation using the distance entropy function as the insert calculation function in terrain surface fitting and deal the visualization with grid method. I consider the distance factor and combine the Shannon Entropy theory to educe the distance entropy function, then use it as the insert calculation function. The distance entropy function make a good terrain surface fitting effect and extend the application field of Entropy theory as well as the calculation method of curved surface fitting.The tree is an important subaerial object witch should be vividdly described and expressed in 3D GIS.People have do someresearch about the tree model in 3D GIS,but haven't got a perfect effect. In this article we discuss the methods of 3D tree modeling by Iteration Function System(IFS)and L System based on the fractal. At the same time, we compare the two methods from the application of tree modeling in 3D CIS and give the class definition of tree object from the Object Oriented point of view, in order that the tree object can be applied in 3D GIS. All this research find a new and effective way for the visualization of tree in 3D GIS.I did Object Oriented analysis and design for the terrain and tree visualization system in 3D GIS at the last part of my article.