| 摘要 |
PROBLEM TO BE SOLVED: To erase the hidden surfaces of map data fast without special hardware by controlling a process for dividing the map data in mesh units according to whether or not there is a hidden surface in a three-dimensional map. SOLUTION: The map data of a map, roads, character strings, etc., are divided into geographical meshes 2001 constituting a geographical surface and the geometrical meshes and divided map data are drawn in order from far away from a viewpoint to nearby the viewpoint to display a three-dimensional map on an output device 2. A geometrical mesh arithmetic means calculates a visible area of the map displayed on the display screen from the viewpoint position and elevation angle and generates rectangular geometrical meshes representing the geometrical surface from altitude data present in the visual area. A hidden-surface presence/absence decision means performs projection conversion by a projection converting means for the generated geometrical meshes and decides whether or not a geometrical mesh which becomes a hidden surface from the conversion result, and when the geometrical mesh which becomes the hidden surface is present, a map data dividing means divides road data and background data included in the map data in geometrical mesh units. |
