Patent US 5,455,896

A three-dimensional geometry processing system generates an intersection curve between two surfaces, an intersection point between a surface and a curve, an intersection point between three surfaces, and a parameter of a surface at a given point. In this system, candidate points for endpoints of an intersection curve between surfaces are generated and stored in a table, a judgment is made whether or not a tracing of intersection from one of the candidate points in the table can be performed, and, if it is judged that the tracing can be performed, a direction in which the tracing is performed is determined. Convergence calculations are performed so that a leading point of a tracing vector lies on both the two surfaces. Determination of the tracing direction and performance of the convergence calculations are repeated until a predetermined end condition is satisfied, thereby generating a set of points on the intersection curve between the surfaces and generating a sequence of curves which forms the intersection curve to be generated.