Abstract: In a rendering device Urend1, a processor 1 receives object data Dpol which defines a polygon by shape, and object data Dlin which defines a line by shape. The processor 1 also receives mesh data Dms which specifies a three-dimensional mesh representing a shape of a ground surface. Based on thus received object data Dpol and the mesh data Dms, the processor 1 generates intermediate data Dlm3 which represents the polygon mapped onto the three-dimensional mesh. Further, based on the received object data Dlin and the mesh data Dms, the processor 1 draws the shape of the line on the three-dimensional mesh so that display image data Ddisp which can display a three-dimensional image including the polygon and line drawn on the ground surface is generated. In this manner, realized is the rendering device Urend1 capable of generating the display image data having no deformation on lines when displayed.

Abstract: A polygon rendering device Urend carries out a polygon division process, in step S36, for generating, based on polygon data which specifies a polygon to be rendered, a plurality of partial polygon data each specifying one piece of partial polygons which are obtained by dividing the polygon. Then in step S37, a rendering process is performed based on the partial polygon data generated in step S36 so as to generate image data which represents an image of the polygon. Here, each of the partial polygons includes a plurality of triangles which respectively include a vertex of the polygon, and each of the triangles included in each of the partial polygons shares at least one edge with any one of the triangles included in the same partial polygon. In such a manner, the polygon rendering device Urend can render polygons at high speeds.

Abstract: When a user indicates a portion of a map to be enlarged or contracted, a surface generating unit generates surfaces by gradually changing a surface from a first shape to a second shape, the first shape corresponding to a position of a map portion previously indicated and the second shape corresponding to a position of the map portion currently indicated. A mapping unit maps the map onto the generated surfaces in sequence, to obtain mapped images. A projecting/displaying unit sequentially projects the mapped images onto a flat virtual screen, and displays the projected images. Thus, the desired portion of the map can be enlarged/contracted, while maintaining connections of roads. Also, the map display can be transformed smoothly, even when the target of enlargement/contraction changes from one map portion to another according to the user's indications. This helps the user comprehend the contents of the map quickly and accurately.

Abstract: In a map display device, a surface storing unit stores surface information which defines a curved surface having a form that depends on positions of portions of a map which are to be enlarged and/or contracted. A mapping unit maps the map onto the curved surface defined by the surface information. A projecting/displaying unit projects the mapped map onto a flat virtual screen, and displays the projected image. Here, by defining the curved surface so that each part of the curved surface forms an intended angle with a line of sight in the projection, the image is displayed with desired portions enlarged and/or contracted, while maintaining connections of roads. The same effect can also be achieved by projecting the map onto a virtual screen having the form of the curved surface.

Abstract: This invention relates to map displaying system, in which the reference altitude value determining means obtains a reference altitude value in accordance with the altitude data in the specific area, and the altitude data changing means performs the processing that each altitude both in the plane area and the solid area have the continuity from one area to another. And the 2-dimensional road data storage means stores the 2-dimensional ground road data and the 2-dimensional underground road data separately. Therefore, the 3-dimensional road data preparing means prepares the 3-dimensional ground road data in accordance with the 2-dimensioanl ground road data and the altitude data, while preparing the 3-dimensional underground road data in accordance with the 2-dimensional underground road data and the altitude data.