Method for producing planar geometric projection images

DETAILED DESCRIPTION Accordingly, it is an important object of the present invention to provide an improved method in which changes in the number of objects represented in a planar geometric projection can be accomplished expeditiously, and in which the visibility of the edge line segments can be quickly and more efficiently determined after a change in the number of objects in the model.
Further objects and advantages of the invention will be apparent from following description and the accompanying drawings.
In carrying out the invention there is provided an improved method for changing a planar geometrical projection image of a compound physical structure which is comprised of a plurality of component objects having separate boundary faces, the method comprising separately storing information for each object on each segment of each edge line formed by an object face edge, edge lines being segmented at line of sight intersections with other lines representing contour edges of visible faces, checking each edge line segment against all visible faces to be represented in the image to determine which edge line segments are visible and which are invisible, including information on visibility with the information stored for each edge line segment, and then modifying the image by changing the number of component objects and after each change in number of objects checking edge line segments for visibility only with respect to the changes associated with the changed objects.