| 摘要 |
PURPOSE:To reduce the necessary amount of data and shorten a processing time by processing hidden lines of a torus display by a two-dimensional process in which the intersection of a ridge line and a section on a projection plane is found. CONSTITUTION:The conversion process of various elements by parallel movement and rotation is normalized so that a plane which contains the (z) axis of a tours coordinate system and is perpendicular to the projection plane coincides with the yz plane of a reference coordinate system. Cases of ways of viewing a torus are classified according to the relation between the (z) axis of the normalized tours coordinate system to the reference (z) axis, and the process is branched to a case where the torus is viewed from just beside, a case where only the front inside ridge line is viewed, a case of the front inside ridge line and part of the inner inside ridge line are viewed, a case wher the front and inner inside ridge lines are viewed continuously, and a case where the tours is viewed from right above. A ridge line for calculating the intersection of the inside ridge line and the elliptic shape of the section at a start and an end point is determined, so the intersection with those ridge lines are found to identify hidden line parts, which are recessed along with other elements to determine display lines, thereby converting the coordinates of the display lines by the reverse conversion of the normalization. |
