| 摘要 |
PURPOSE:To effectively display a two-dimensional line graphic by drawing again the three-dimensional shape data by using a hidden surface erasing area formed when a set of polyhedrons is drawn, thereby deleting the segments which are not seen from a visual point even for a complicated shape. CONSTITUTION:When a two-dimensional line graphic is drawn based on the three-dimensional shape data, a three-dimensional shape is defined as a set of polyhedrons and a three-dimensional shape is drawn by means of a high speed hidden surface erasing function prepared to the polyhedrons. Then the three-dimensional shape is drawn again by using a hidden surface erasing area 4. When a hexahedron 2, for example, is drawn, only the surfaces A, D and E of the hexahedron 2 are drawn with the erasion of the hidden surfaces. Then the depth areas A', D', and E' of the surfaces A, D and E respectively are recorded in the same in the same viewfield from a visual point 1 in the area 4. Therefore a display screen where the segments Cg, fg and gh are not drawn when 12 segments which are equal to the depth of the area 4 or close to the point 1 and constitute the hexahedron 2 are drawn. |
