Incorporating Free Form Features in aesthetic and engineering product design: State-of-the-art report

The use of free-form shapes has become mainstream to design complex products that have to fulfil
engineering requirements as well as aesthetic criteria. Even if today's CAD systems can easily represent
free-form shapes by means of NURBS surfaces, their definition and modification still require a deep
knowledge and a great skill in the manipulation of the underlying mathematical models. The
implemented free-form shapes design operators are time consuming and do not enable fast
modifications. To overcome these limits, some researches have been undertaken to try to adapt the
feature concept, successfully adopted for the design of regular shapes, in the free-form domain. It gives
rise to a set of free-form featuresmodelling strategies. This paper gathers together the state-of-the-art of
these advances. The various approaches are depicted and compared with respect to a very precise set of
criteria expressing the needs in aesthetic and engineering designs. The limits and future trends are
presented