||3D GIS is the key point of the development in the area in geospatial information domain. 3D visualization techniques, including 3D terrain data processing, the 3D objects modelling , satellite or air photo image texture, model material, level-of-detail terrain, is already gradually mature and had the outstanding performance in the existing 3D GIS software. But 3D spatial analysis function was still lacking in the field of the 3D spatial data processing.|
The goal of this research is to develop a 3D spatial analysis function for sun shadow in horizontal and vertical direction and to construct a system for 3D geographic objects visualization by using MFC and OpenGL as the development kit. It has some fundamental functions including: camera control, selecting a single face of a object, linking to a database, level-of-detail terrain. The shadow volume algorithm was used for 3D shadow visualization, and light tracing algorithm was used to compute a single face’s culling area, finally sunshine formula of four seasons was utilitized to realize the shadow analysis function.