Specification of freeform features

Freeform feature modeling is an extension to feature mod-eling in which, in addition to regular-shaped features, also freeform features are possible. Due to the large variety of freeform features, a generic approach to specify such fea-tures is required. This paper describes such an approach. A freeform feature class is specied by using a prototype and constraints. The latter are used to dene intuitive parame-ters and validity conditions for the class. A new, prototype-driven constraint solving method is used to unambiguously determine a freeform feature during the specication both of a class and of an instance to be added to a model. The speci cation of freeform features and the prototype-driven constraint solving method are discussed. Several examples are given