Abstract
Robust differential equation solvers which can be applied in tracing intersection curves of surfaces are discussed and recommended for use in regions very near to singular points. And also behaviours of intersection curves around the singular points are analyzed, because the differential equations do not hold at the singular points where normal vectors of the two surfaces become parallel. With these two approaches tracing of intersection curves can be confidently performed even in critical cases and the tracing time is automatically adjusted in accordance with difficulty of the tracing. Numerical examples of critical cases are shown.
