Methods and techniques for advanced curve and surface modeling

This paper concentrates on the modeling of complex surfaces over arbitrary topologies. Methods and techniques newly developed are presented for high-quality curve and surface modeling in CAD system, e.g., composing of rectangular and triangular patches, modeling of closed surfaces over polyhedral topologies, blending free-form surfaces with geometric continuity. The data structure and data exchange are based on STEP, the international standard for external representation of product data. NURBS (Nonuniform Rational B-spline Surface) representation is adopted as a unified approach to advanced curve and surface design.