关键词: 地形可视化, 细节层次, 剪切图, 重采样, 视锥裁剪, 包围体

Abstract: In the real-time rendering of large terrain, it is the contradiction between large terrain data and the limited data communication bandwidth of the hardware that affects the rendering efficiency. The survey was based on the Geoclipmap algorithm and some improvements were made to solve the problem. During the data preprocessing, a Geometry Scene Graph （GSG） structure was used to organize the terrain data in order to improve data loading speed, and the implementation used a sinc function as the filter in the generation of mipmap levels to avoid detail of terrain surface being flattened. After that, it is the rendering process. A two-level view frustum culling was presented which was based on the bounding spheres hierarchy and normal computation was put in the fragment shader of Graphic Processing Unit （GPU）, which reduced the data stream between CPU and GPU. Just as the simulation results show, the algorithm can keep the fidelity of terrain and be effective to meet the needs of large terrain rendering.

Key words: terrain visualization, Level of Detail (LOD), clipmap, resampling, view frustum culling, bounding box