Abstract: When a plurality of coplanar shapes are rendered over one another by performing a hidden surface removal operation using the Z value, a reference plane is specified, and the Z value of each point of a shape to be rendered on the reference plane is uniquely calculated based on the Z value of the rendering start point, the Z value gradient dZdx for the X direction, and the Z value gradient dZdy for the Y direction. Thus, any coplanar shapes will have the same Z value for each point shared therebetween. Therefore, if the rendering process is performed under such a rule that a shape is overwritten when the Z value of the new shape is less than or equal to the current Z value, it is ensured that the previously-rendered shape is always overwritten with a later-rendered, coplanar shape. Thus, it is possible to prevent a phenomenon that some pixels of a later-rendered shape that are supposed to be displayed are not displayed.

Abstract: A car navigation system capable of performing both real-time route guidance for a driver, and non-route-guidance display and operation of car navigation functions such as destination setting and vicinity searching for a non-driver, without necessitating a high-speed CPU or a high-performance drawing processing section. A display apparatus 200 is equipped with a CPU 210, an operating section 220, and drawing processing sections 230 and 240 corresponding to two display screens 250A and 250B, navigation-related processing is performed in a navigation apparatus 100, and drawing processing for the driver and drawing processing for a non-driver are executed independently by drawing processing sections 230 and 240 respectively of display apparatus 200. Functions are shared between navigation apparatus 100 and display apparatus 200.

Abstract: When a plurality of coplanar shapes are rendered over one another by performing a hidden surface removal operation using the Z value, a reference plane is specified, and the Z value of each point of a shape to be rendered on the reference plane is uniquely calculated based on the Z value of the rendering start point, the Z value gradient dZdx for the X direction, and the Z value gradient dZdy for the Y direction. Thus, any coplanar shapes will have the same Z value for each point shared therebetween. Therefore, if the rendering process is performed under such a rule that a shape is overwritten when the Z value of the new shape is less than or equal to the current Z value, it is ensured that the previously-rendered shape is always overwritten with a later-rendered, coplanar shape. Thus, it is possible to prevent a phenomenon that some pixels of a later-rendered shape that are supposed to be displayed are not displayed.