| 摘要 |
[Problem] To display a three-dimensional map over the whole display area with a relatively light load. [Solution] A high-definition model database 17 for expressing a planimetric feature in detail and a simple model database 16 for simple expression are prepared as map databases. When displaying a three-dimensional map, a simple three-dimensional map is drawn in a whole display area using the simple model, and for a high-definition model drawing range within a prescribed distance from a viewpoint, a high-definition three-dimensional map is drawn in another layer using the high-definition model. The high-definition three-dimensional map is superposed in front of the simple three-dimensional map, and the two are then combined together to cause the three-dimensional map to be displayed. At this time, the high-definition three-dimensional map near the border with the high-definition model drawing range is drawn translucently, and both are thereby merged without a sense of incongruity. Furthermore, when there is a viewpoint near the border where the high-definition model is provided, the whole of the high-definition model is drawn translucently, thereby making it possible for the high-definition three-dimensional map to be gradually rendered transparent and transitioned to the display of only the simple three-dimensional map without a sense of incongruity. |
