A feature-based approach for design of free-form objects

摘要

This paper presents a method to build a Hermite-based surface model generated from an existing free-form object. Such a method provides both C{sup}2 continuity across adjacent patches in a surface region and G{sup}1 continuity across adjacent surface regions. The model then serves as the basis for new shape designs of the free-form object. Among objects of complex-shaped features, human masks, shoes, gloves and artificial limbs are instances of particular interest. The method not only determines surface regions (the highest-level features) in an object and sub-features (lower-level features) in each region, but also demonstrates how low-level features be blended into high-level ones. By means of parameterized features, new products are created according to the change of parameter values. Variables and constraints of features are regarded as key elements in defining design rules for a free-form design system. The coordinate measuring machine (CMM) obtains 3D data points of an object while a criterion selects the measuring path of fewest points so as to extract surface features for a variational design. A range of shoe-last designs exemplifies the practice of this proposed methodology.