| 摘要 |
PURPOSE:To permit labor saving in a memory and to shorten a processing time by deciding a virtually set point for decision by the apex data of plural points. CONSTITUTION:A painting-out processing part 3 inputs graphic data being map information read out from a CD-ROM 9b, selects four apex data which continue in the clockwise direction of a polygon, and stores them in a work RAM 4. In the first decision, it is decided in what direction a 2nd point B exists in the case of viewing from a 1st point A, and in the second decision, the virtual inner point P which is set in a certain direction in the case of viewing from the 2nd point B is compared with the direction of a 3rd point C. Then, the third decision is performed in the case that the direction of the 3rd point C exists in a counterclockwise direction excepting the case that it exists in the clockwise direction more than the point P with center at the 2nd point B so as to decide whether or not the line segment linking a 4th point D with the 3rd point C intersects with the line segment linking the 2nd point B and the point P. Thus, the capacity of the memory is decreased, the time required for decision is shortened and painting-out is early started. |
