| With the concept of "Digital Earth" and "Global Information Grid" and the increase of people’s knowledge, the gathering method of3D data has changed from partial scale, city scale, and global scale. Science research, military research, industrial application etc. are all based on big spatial data. GIS is transforming from2D to3D, and it changed our lives. With the development of3D GIS, it can include and describe richer spatial data, break the2D display gap, and reborn the real feelings of reality. All of above is concerned by the industry and academic.In3D GIS systems, Google Earth and other3D GIS software can draw the image quite well, and the image render technology is widely used. But in the three-dimensional virtual earth vector applications due to the presence of the bottleneck, problems are not solved. The3D GIS software can only render large scales of vector data with poor accuracy, and can not query and analysis directly. In addition, large vector data organization, query, statistical analysis, drawing, etc need further research, will soon become practical, among them, provide an efficient vector data of3D data organization and rendering solution is the basis of3D vector data query, analysis, statistics and decision support, is a very important and challenging problem of three-dimensional GIS system.This paper is aiming at the urgent demand of drawing3D vector data, focus on the screen render precision and isolated phenomenon of the geometric render method. The main research of the method is to find a non-scale simplify method of vector data based on semantic information, a interpolation algorithm based on screen render precision, interpolation data amount and terrain data, an organization of vector dataset and other key problems, results are obtained in the following innovative:(1) By analyzing the main problem of vector data rendering, a5tuple model is presented. The5tuple model includes:drawing data source, vector data preprocessing, vector data organization and storage,3D rendering method and three-dimensional vector drawing results evaluation method,, at the same time, the research on the problem of the field has carried on the summary and classification.(2) Studied the relative optimization algorithm for3D linear interpolation of vector intersections in flat area. First of all, through the definition of screen rendering N pixel deviation or pixel distortion value, given the form of measurement method of screen plotting accuracy. Research on Dynamic Interpolation of3-D vector drawing in the presence of screen rendering accuracy optimization and interpolation data volume optimization are isolated phenomenon, combined with insufficient phenomenon, put forward considering N pixel screen rendering distortion optimization precision terrain grid model, construction of a given algorithm. Based on this, proposed based on the three dimensional linear vector intersection point interpolation optimization concept vertex sets of topography optimization grid model, gives the optimization algorithm for solving vertex set, the method uses polygonal mesh after optimization to interpolation of vector data, put forward the corresponding N optimization element distortion correction and interpolation terrain mesh vertices. To realize the real-time correction of mesh optimization under extreme conditions.Experiments show that this method can reduce the vector data interpolation data, significantly improve the efficiency of vector data rendering.(3) proposed a construction strategy and method of river network structure based on genetic algorithm:regard the river network structure of the problem as a preferred the mainstream, regard the mainstream problem as an optimization problem, regard the global optimization problems as the semantic information. Put forward the solving strategy using genetic algorithm. To obtain the River mainstream, establishes the hierarchy of the river, and do the experiments to verify the effectiveness of the proposed scheme. Genetic algorithm can consider the topological relationship, vector data of hydrological data, semantic data, and also can find the river mainstream more accurately. After confirming the River mainstream, using the Horton code to classify and structure the stream data, than followed by three dimensional environment continuously integrated dynamic decomposition scale, a non-scale generalization can be performed.(4)Research studied a non-scale generation method for river network screen display. It can classify and structured using Horton code after determine the mainstream. After t hat a simplification will be placed and using the generation operator to do the non-scal e generation.(5) Putting forward a kind of3D vector data organization method, with equal longitude latitude grid way to partition the sphere, to establish an incomplete region four fork tree, than a new structure contains the original vector data and topographical data, the optimized vector data and topographical data, the simplification of the vector data and the data block metadata is established. Use this new data block as the basic elements of the the Pyramid to establish the vector Pyramid. And use a large file+index to realize quick query the server for vector data block.(6) Proposed a dynamic optimization draw method. When drawing vector data, make full use of the multi-scale data after map generalization and multi level optimization of grid in each grid, minimize the rendering distortion situation, as far as possible to improve rendering efficiency.(7) Developed a prototype system of3D vector drawing to verify the theory and methods presented in this paper. Using typical data to do the related experiments to verify the correctness of the theory and method proposed in this paper. |
