提出了一种新型三角形簇作为GPU的图元绘制单元,结合LOD技术实现了自适应的无裂缝地形渲染.该三角形簇,称为N-簇,分为8种基本类型,不同尺寸和位置的地形网格块都可以通过这8种基本类型进行缩放和平移得到.采用二叉树数据结构组织N-簇,每个二叉树节点对应一种N-簇,同时存储了N-簇的缩放及平移.结合八边形误差算法进行场景LOD的构建,避免了不同LOD层次间过滤产生的T-连接.由于大规模地形的高程数据量及纹理数据量非常庞大,不能一次性载入内存,采用四叉树数据结构分块组织高程数据和纹理数据,在程序运行时进行数据块的动态加载.实验结果表明,N-簇提高了地形三角形网格的绘制效率,同时,整个算法能自适应地进行无裂缝地形渲染,并能满足大规模地形场景实时绘制的要求.%A new kind of triangle cluster, as the render unit of GPU is proposed, combined the LOD technology, which realizes the adaptive terrain rendering with no crack. The new kind of triangle cluster, called N-cluster, has eight base types and the terrain mesh with different size and location can translated from the base types with scaling and translating. Binary tree is used to organize N-cluster, each node contains the information of N-cluster, including type, scale and translation. Octagon metric is utilized to construct LOD of terrain, which can avoid the T-adjacent between different LOD. Because of the massive data of DEM and texture data, which cannot be loaded into memory once, the quad tree is used to organize them and the data mesh is loaded into memory dynamically when running. The experimental result shows that, N-cluster improves the efficiency of terrain rendering, and the total algorithm can adaptively rendering terrain without crack, which can also meet the requirement of real-time rendering of large-scale terrain.
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