Interpreting engineering drawings of polyhedrons

A system is discussed that restores solid models, or a set of polyhedra consistent with a given set of three orthographic views which are input by using a facsimile device. Emphasis is on the description of two novel techniques: the line-segment extraction method and the polyhedron restoration method. The line-segment extraction is performed by using a probe, a small fragment of line, which moves along the central axis of each line segment represented by a binary image. Therefore, the method does not require any preprocessing such as noise elimination, or thinning of the given binary image. The polyhedron restoration method uses a face-oriented approach, rather than the conventional wire-frame-oriented approach. The method is basically a combinatorial search procedure that finds all of the legal combinations of possible faces