模板阴影体是矢量地图3维绘制的一种主要方法,使用线段、多边形等基本的几何图形在3维地形上叠加显示地图要素,因表示形式过于简单,导致其传递的地图要素信息十分有限。为此,对模板阴影体方法进行扩展,提出矢量地图在3维地形上的符号化叠加方法,以提供更丰富的矢量地图3维显示样式。首先,简述基于模板阴影体绘制矢量数据的基本原理。然后,提出对模板阴影体的扩展,包括保持符号边缘光滑的算法和符号轮廓描边、交叉压盖的处理方法。实验结果表明,该扩展方法能够实现矢量地图在3维地形上的实时叠加显示,符号化绘制显著提高了矢量地图显示效果。

Stencil shadow volumes are the main 3D rendering method for vector maps. Basic geometric graphs, such as lines and polygons, are the main representation of map features. These representation forms were so simple that strictly limited map feature information had been transferred. Consequently, in order to enrich the 3D visualization styles of a vector map, an extended rendering method based on the stencil shadow volumes is presented, which realizes real-time symbol overlaying of a vector map on terrain. First, the basics of vector data visualization based on the stencil shadow volume theory are reviewed. Second, the extended method is introduced, which includes border smoothing with rounded caps, while dealing with outlines and overlaps. Finally, the experiment results show that a real-time display of vector maps on terrain can be achieved and that the visualization effects have been improved by cartographic symbolical overlay.