Modeling Of Large Scale Terrain And Optimization Of Rendering Efficiency For Free And Whole Roaming

Recently, the terrain data has been deepening in precision and extent with the development of the space map technology. Global terrain data has appeared. It is a research hotspot how to effectively organize the terrain data, carry out out-of-core model on the large scale terrain, and achieve the terrain roaming freely and wholly. The research goals of this paper are modeling of the large scale terrain where we can roam freely and wholly and optimization of its rendering efficiency. The work plays an important role in building the large scale visualization of spatial information system.Firstly, after analyzing the latest international research findings of terrain out-of-core modeling algorithms, it was discovered that both whole and local terrain information should be considered. It is the key to achieve large scale terrain roaming freely and wholly. The double-layer frame terrain model was presented. The model is called up-quadtree sub-binary tree. It was built on the multilayer data of multi-resolution designed by Lindstrom and the progressive grid designed by Hoppe from Microsoft Research. The tree in the model keeps managing the whole scale terrain data, and sets up cache memory for the view-dependent local terrain while rendering the local terrain. This model utilizes a circular planar array to access the terrain patch data, uses double threads to load and render terrains in real time, and achieves the display of terrains rapidly and smoothly. The cracks were avoided in the double-layer frame terrain model by force undisection role.Secondly, the rendering efficiency was optimized at both aspects of the whole area and the local one based on building a terrain model. This paper principally studied about constructing a saturated quadtree ball over the whole scale to cull view frustum up-to-down, drawing local grid by Cluster Triangulations, and using vertexarray to improve the large scale terrain rendering efficiency.Thirdly, the large scale terrain visualization system was designed and realized to validate the effectiveness of the double-layer frame terrain model. As a result, the system could achieve a good visual effect and a high frame rate, and implement roaming freely and wholly on the large-scale terrain. Finally, the double-layer frame terrain model was applied in the 863 issue on large-scale visualization system. It was realized that high speed rendering and roaming on large space scene.The double-layer frame terrain model plays an important role in studing large-scale terrain panorama roaming technology.