分布式大规模球形地形系统的研究与实现

发布时间：2018-03-16 18:08

本文选题：球形地形　切入点：正六面体剖分　出处：《电子科技大学》2013年硕士论文　论文类型：学位论文

【摘要】：经纬坐标系是一套被广泛使用的地理坐标系统，在构建球形地形模型时，很自然地想到可以按照经纬坐标剖分网格。然而因为经纬坐标是根据角度确定的，导致剖分后同一层次的不同网格面积覆盖差异较大，并最终导致数据大量冗余的问题。为了解决这一问题，，本文提出了正六面体剖分算法。该算法是指对正六面体的每个面都进行四叉剖分，然后将剖分后的网格从正六面体中心投影到其外接球上，这样便得到球体的剖分网格。虽然使用该算法剖分后同一层次不同网格的覆盖面积依然不等，但却能保证构成网格的四条弧的长度相等，其最终效果便是面积相差不大。充分利用该算法剖分后网格与原网格的自相似性，以及正六面体六个面的对称性，可以极大地简化运算，提高系统效率。面对球形地形的大规模高层和纹理数据，本文利用剖分算法将其组织为金字塔结构，并采用压缩算法将其打包压缩。数据调度管理方面，构建了分布式数据服务器，在服务器中又建立了数据缓存，以实现数据的快速调度与共享。本文设计的绘制系统主要特点是跨平台，甚至包括近年迅速发展的移动平台。绘制时首先按照剖分算法更新四叉树，在更新的过程中执行视锥裁剪，并利用屏幕误差构造球形地形的多分辨率模型，裂缝问题则通过结合使用丢弃顶点和线性剖分准则而得以巧妙地避开，最后通过OpenGL接口使用GPU加速完成绘制，实现了一个支持实时漫游的原型系统。
[Abstract]:The longitude and latitudinal coordinate system is a set of widely used geographical coordinate system. In constructing the spherical terrain model, it is natural to think that the grid can be divided according to the longitude and latitude coordinates. However, because the longitude and latitude coordinates are determined according to the angle, As a result, the coverage of different mesh areas at the same level is different, and the problem of redundant data is caused. In order to solve this problem, an algorithm of regular hexahedron dissection is proposed in this paper, which means that every plane of a regular hexahedron is quadrilateral, and then the meshes are projected from the center of the regular hexahedron to the outer ball of the regular hexahedron. In this way, the meshes of the sphere are obtained. Although the coverage of different meshes at the same level still varies with the algorithm, the length of the four arcs that make up the mesh is equal. Using the self-similarity between the mesh and the original mesh, and the symmetry of the hexahedron, the algorithm can greatly simplify the operation and improve the system efficiency. In the face of large-scale high-level and texture data of spherical terrain, this paper uses the partition algorithm to organize it into a pyramid structure, and uses a compression algorithm to package and compress it. In the aspect of data scheduling and management, a distributed data server is constructed. The data cache is established in the server to realize the fast scheduling and sharing of data. The main features of the rendering system designed in this paper are cross-platform, even the mobile platform that has developed rapidly in recent years. When drawing, quadtree is updated according to partition algorithm, and cone clipping is performed in the process of updating. The multi-resolution model of spherical terrain is constructed by using screen error. The crack problem can be avoided skillfully by combining discarded vertices and linear partition criteria. Finally, GPU is used to accelerate the rendering through OpenGL interface. A prototype system supporting real-time roaming is implemented.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：P208

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