Abstract: A method of and an apparatus for producing solid models, in which input data consisting of the coordinates of terminal points and a formula of a curved line of each arc of a given wire frame model is read. The coordinates of a node and a set of arcs connected thereto are determined based on the input coordinates of the terminal points. A set of arcs looping around an indivisible surface of the wire frame model are specified as the outermost line surrounding the whole wire frame model. A region of the wire frame model surrounded by the outermost line or division lines is divided into two new partial wire frame models by a new division line starting from a node located on the outermost line or the division lines, traversing the region without making a loop, passing along each of the arcs included in the region only once, and reaching another node located on the outermost line or the division lines.

Abstract: Creating a solid (i.e. three dimensional) model with a CAD system, from a two dimensional representation, includes dividing the two dimensional representation into a plurality of shape portions, inputting them into the CAD system, rendering them solid, and then connecting them into the desired solid model. Among the shape portions are those whose cross-sections are substantially uniform. In inputting, the operator of the CAD system need only input line segments of the shape portions in approximately the correct orientation.