| Realistic three-dimensional terrain and natural landscape are elementary parts of virtual reality and visualization system. However, the massive data is not easy to real-time dispay and process under the condition of limited showing hardware of graphics.Techniques of 3D terrain visualization typically include three main fields that the construction of terrain surface, the storage and schedule of terrain data and the simplification of terrain data; Although each of the three parts has some good algorithms, but how to combine their respective advantages is needed to research. Using RSG when lower requirement on the terrain details in the system, in order to solve the problem of scheduling the redundent data into memory each time, use the improved method of terrain block to reduce the amount of data for each treatment; Existed culling algrithm will also produce a lot of redundant data, the paper uses combination of the surrounding cone and surrounding ball; In order to show realistic terrain effects with less terrain data, use the improved terrain LOD simplification method based on triangle binary tree. Often use TIN While the system requirements the high details of terrain, but it is hard to orgnize, in order to reduce the difficulties, use the method based on RSG as far from the viewport and adopt the method based on TIN as near by the viewport. Using different node evaluation system and crack repair methods between near and distance. Thus, not only combine both advantages of RSG and TIN, but also reduce bad influence of their shortcoming on system.Natural landscape can increase the reality of virtual reality. They can be realized by particle system, such as rain, snow, fountain and so on. In order to speed up the display speed further, in order to show real results with less particles this paper uses LOD method to distribute particle emitters that reduces the number of particles. The results of experiments show the correctness and effectiveness of this algorithm. |
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