Large-scale Three-dimensional Terrain Visualization And Roaming Key Technology Research

Recently,Large-scale 3D terrain visualization,which is an important research area of 3D computer graphics, and is the core portion of 3D graphics rendering engine, has been widely applied to many applications and fields of study, such as 3D games, virtual reality, battlefield simulation, 3D-GIS and so on. It With the wide use of 3D visualization applications and the continuous evolution of computer hardware technology, higher performance of rendering is required in large-scale terrain rendering. Accompanied by the development of remote sensing technology, access to terrain elevation information and earth imagery has also got a rapid development, which provides the basic data for the development of 3D-GIS. In the field of 3D-GIS, large-scale terrain rendering is its most basic, most central part. This will help users understand the relationship of the spatial data and the analytical result. Large-scale terrain rendering is also an important part of constructing digital earth.This thesis comes from the actual 3D-GIS project, relying on the national terrain elevation information and image data, this paper implements a large-scale real-time terrain rendering system, which provides the basic platform for urban planning, flood control and virtual reality applications. As this paper's research work,firstly, summarizes the origin of large-scale terrain rendering, development, typical algorithm and related work at home and abroad;secondly, the paper provides detailed describe of the mathematical foundation and the 3D terrain model generation technologies, including 3D common coordinate system, mathematical transformation, graphics rendering pipeline, and terrain visualization technology;then, proposed a solution using pyramid model technology to solve the multi resolution issues of large scale virtual terrain environment. Combining with LOD technical, I design and realize a method for large-scale terrain rendering with pyramid model, and gives a detail description of the block layer rules, methods and structure;finaly, this paper realizes a real-time rendering system of large-scale terrain based on quad-tree method, and makes a research and improvement for loading and rendering large-scale urban models.Results of this study have been used in the field of 3D-GIS, including land use management systems, monitoring system of mining, management system of small towns and so on, these visual system has a common feature, that is the large scale terrain data.