| 摘要 |
PURPOSE:To enable only an equivalent triangular plane element in a small number of grids to be set as the object of decision and to shorten retrieval time when decision processing whether or not the apex of the triangular plane element is already registered on an apex list is performed by managing information with respect to the equivalent triangular plane element in memory in unit of grid. CONSTITUTION:The information with respect to the equivalent triangular plane element is managed in the memory in unit of grid. Therefore, only the apex of the triangular plane element in the small number of grids can be set as the object of the decision when the decision processing whether or not the apex of the equivalent plane triangular plane element found by a triangular plane element calculation means 5 is already registered on the apex list is performed. In other words, another triangular plane element sharing the found apex of the triangular plane element ought to exist in the grid N1 or either 26 grids adjacent to the grid N1. The comparison of the apex with the coordinate value of the apex of a found triangular plane element is performed only by performing the comparison of already calculated another triangular plane element in the grid N1 with all the apexes of the triangular plane elements in 13 adjacent grids except for the grid N1. In such a way, retrieval processing time can be shortened. |
