大规模地形场景真实感建模与绘制是虚拟战场、地理信息系统、三维游戏仿真等领域的基础。随着应用的不断扩展和深入，人们对地形场景的规模、绘制速度及仿真精度提出越来越高的要求，所以长期以来该课题一直是国内外计算机图形学领域研究的热点之一。 本文对基于四叉树LOD地形真实感绘制关键技术进行了深入的研究。主要分析了基于四叉树的LOD地形模型的算法思想及其存储结构；对以往采用的六面体视景体判别方法进行了优化，引入一种建立扇形裁减区域的方法，简化了算法的复杂度，提高了渲染效率；在对场景进行背景剔除时，采用一种判断视线和地形多边形法线向量夹角余弦值的方法来提高效率；通过视点相关的误差计算和考虑地形粗糙度引起的静态误差的计算，建立了地形节点评价系统；对地形裂缝产生的原因及处理方法进行了分析，采用了一种改变T型节点连接方式的方法对裂缝进行了修补。 随着图形处理器(GPU)的发展，鉴于传统的依靠CPU的绘制算法不能充分发挥图形系统性能的缺点，在借鉴基于四叉树LOD地形模型绘制方法原理与思想的基础上，对基于GPU的Patch-LOD地形绘制算法进行了深入的研究。分析了顶点（索引）缓存中的数据存储方式，引入了地形瓦片金字塔模型的数据组织方式，给出了基于索引模板的地形绘制算法流程。地形裂缝的处理方面，采用在地形块的四周加一个“裙边”的方式解决。 最后，利用OpneSceneGraph2.9.5和VS2005软件平台，结合本文研究的相关算法和方法实现了大规模三维地形场景渲染系统和雪效粒子系统。实验结果表明，该系统能实时、快速的完成大规模多分辨率地形的真实感绘制。

In the fields of virtual battlefield, GIS systems and 3D game simulation, large-scale terrain realistic rendering is the most basic content. With the expanding and deepening of the application, people’s requests are getting higher and higher on the terrain scene scale, rendering speed and the simulation accuracy. So, for a long time, large-scale terrain realistic rendering is one of hot spots in the field of computer graphics from home to abroad. In this paper, several key technologies of terrain realistic rendering based on quadtree LOD is deeply studied. Mainly analyze the algorithm thought and storage structure based on quadtree LOD terrain model. The discriminate method is optimized which is used previously, and introduced a new method which establish fan-shaped cuts area. This method can simplify algorithm complexity, and improve the rendering efficiency. Adopting a method which judge the view and terrain polygon normal vector` cosine value to improve the efficiency when eliminate the background of the scene. By using the view-dependent error computation and considering terrain roughness calculation of static error caused, establishes the terrain node evaluation system. The causes of cracks and processing method are analyzed, using a method that change T node connection type to mend the cracks. Along with the development of graphics processing unit (GPU), according to the traditional method which rely on the CPU rendering algorithms can't fully make use of graphics features ,so in this paper ,we refer to the method of QuadTree Lod terrain modeling algorithm,and deeply study on the patch-Lod terrain rendering algorithm based on GPU. The vertex (index) cached data storage structure is analyzed, the terrain tile pyramid is introduced, and given the terrain rendering algorithm process based on the index templates. Using the method that add a “skirt” in the terrain blocks around to mend cracks. At last, by using OpneSceneGraph2.9.5 and VS2005 software platform, combining the related algorithms and the methods that studied in this paper, we realized the large-scale terrain scene rendering system and snow effect. The result of the experiment shows that the system can achieve large-scale realistic terrain rendering in real-time with multi-resolution quickly.