典型二维矢量地图要素在三维地形表面的贴合渲染算法研究

为使三维GIS在具备真实感场景表达能力的同时，对空间现象或规律，兼具二维矢量地图的抽象与概括表达能力，拟把典型二维矢量地图要素的投影目标从平面拓展到三维几何表面。针对常用的二维矢量地图要素：无符号折线、简单多边形、符号化折线和复杂多边形，分别研究提出其在三维不规则地形几何表面的连续铺展数学模型和方法，消除二维矢量可能会出现的"悬浮"空中、"穿刺"地表、"淹没"地下及变形走样等现象；进一步提出二维矢量在三维表面贴合渲染效果根据视距远近而综合调整的动态模型，以使得渲染效果具有一定的空间距离感；通过建立合适的空间数据模型以及数据调度机制，并基于数据分块以及流水线处理的有关计算方法，建立三维地表及其表面二维矢量地图要素无走样紧密融合的高性能并行渲染算法。在理论方面丰富和发展三维GIS中二维矢量在三维表面投影的有关数学模型和方法，在应用方面丰富和发展三维GIS中有关高性能并行地理计算的实现技术。

3D GIS, in its earlier development, focuses on making the virtual scene looks like a real natural world. With the expansion of application scenarios, it becomes more and more important to introduce the abstract ability of 2D map to 3D GIS, by overlaying 2D vector map elements on the surface of 3D terrain model to outline spatial phenomenon or pattern of earth surface. The primary elements on 2D topographical map include simple solid polyline, symbolized polyline, simple polygon (surrounded by simple solid polyline and filled by only one single color), and complex polygon (surrounded by symbolized polyline or filled by vector or raster texture pattern), and more. Specific mathematical models are researched respectively for continuously spreading typical types of 2D vector map elements over the 3D surface, which ensure 2D graphics seamlessly fit to 3D irregular surface. That means 2D graphics wouldn't suspend above, puncture into, or submerge beneath the 3D surface, and wouldn't lose shape or be distorted. For simple solid polyline and simple polygon, the parallel algorithm for rendering them on 3D surface is proposed to cover the shortage of existing methods. For symbolized polyline, the spreading distance from the line's origin and its symbol pattern are both used to construct the symbolization rule. For complex polygon, the rule, and then the mathematical model, to spread its interior texture over 3D surface are explored. For all the four types of 2D map elements, the methods to synthesize or to simplify rendered pixels according to sighting distance are researched. Based on achieved mathematical methods, by constructing appropriate spatial data model and data scheduling mechanism, in terms of core thought of data parallel and pipeline parallel algorithms, new parallel algorithms are proposed to improve rendering performance of 2D map elements on 3D surface. The research work enriches focuses in the field of 2D vector graphics and its application in 3D GIS.