Symbolic Representation of Vector Map in Virtual Geographic Environment

Those basic geometric graphs such as lines and polygons are the main representations used by 3D rendering methods of vector map at present. It is so simple that strictly limited map feature information has been transferred. Consequently, an extended rendering method based on the shadow volume stencil theory is presented, which allows real time symbolical overlay of vector map on terrain. Firstly, the basis of vector data visualization based on stencil shadow volume theory has been reviewed. Secondly, in order to improve visualization effect, the cartographic symbolization of vector map, i.e. roads, has been dedicated, which includes smooth border with rounded caps, outlines and overlaps. Finally, the experiment shows that real time displaying of vector map on terrain has been achieved, and the visualization effects have been improved by cartographic symbolical overlay.