Computation of Terrestrial Visible Area in Three-Dimensional GIS

Frustum culling is always an important method to accelerate graphic drawing. One method is first organizing geomtry objects into a scene graph, then removing the nodes that is not intersectant between the visible area and the hiberarchy of bounding volume of nodes of scene graph. Another method is first calculating the rang of visible area directly, then drawing the objects that is in the rang. For vector data visualization in 3D of GIS,the second method is more suitable. This article, based on the second method, present respectively an accurate, rapid calculating method of visible area aim at flat land and spherical land, effectively improve the rendering speed of GIS data.