Specification of freeform features

Abstract

Freeform feature modeling is an extension to feature modeling 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 features is required. This paper describes such an approach. A freeform feature class is specified by using a prototype and constraints. The latter are used to define intuitive parameters and validity conditions for the class. A new, prototypedriven constraint solving method is used to unambiguously determine a freeform feature during the specification both of a class and of an instance to be added to a model. The specification of freeform features and the prototype-driven constraint solving method are discussed. Several examples are given.

Processing Free Form Objects within a Product Development Process Framework

“…-curve-based approaches [33,53,54] define parameterized free-form surfaces from a set of parameterized free-form curves;…”

A non-rigid cluster rewriting approach to solve systems of 3D geometric constraints

“…Discontinuous behaviour is undesirable for most parametrisations. For example, in [23], requirements are identified for freeform feature classes and their instances. For users of the feature class, who generally have no knowledge of the constraints used for the parametrisation, discontinuities in the behaviour of the feature are unexpected and undesirable.…”

Developments in Feature Modelling

“…It is, therefore, very important that new user-defined feature classes [4] can be created. A way to do this for freeform volumetric features, which makes use of special definition points and constraints between these points, is presented in [20], and a way to do it for freeform surface features, which makes use of a general classification of freeform surface features [21], is presented in [22]. Freeform feature instances can again be created in a model by determining values for the parameters, but their 'attachment' to other features is more complicated than for simple features, as the feature faces that are coupled can have complex shapes, and therefore usually do not match.…”