An alternative approach for integrated free-form modeling

To reduce the time to market, several strategies have been introduced in the design process. The concurrent engineering methodology has been widely adopted and a lot of work has been done to optimize the communication among the different phases of the product development. The CAD model is central in the product development process; a significant problem in this context is given by the transfer of such a model to the other phases or to other contractors without losing information. In this paper, we propose subdivision surfaces as a potential alternative to NURBS since they are a geometric representation between a discrete and continuous one. They can be introduced as a unique geometric frame supporting different stages since they bypass some of the transfer problems of NURBS. In fact, although NURBS are the de facto standard, they are not able to face efficiently the communication, since resorting to patches in order to correctly represent complex surfaces. One of the main problems of adopting subdivision surfaces in the CAD environment is the lack of high-level tools to manipulate the geometry. In order to allow users to deal with this new modeling technique closer to the way they are used to, a feature-based approach is proposed. In fact, the feature concept is well-known and used in the mechanical context and has been extended to free-form modeling as well. In the paper, features obtainable by generalized sweep operations are defined and treated.