Towards reverse design of freeform shapes J.S.M. Vergeest, R.Langerak, Y.Song, C. Wang Faculty of Industrial Design Engineering Delft University of Technology The Netherlands, Delft j.s.m.vergeest@io.tudelft.nl W.F. Bronsvoort P.J. Nyirenda Faculty of Electrical Engineering, Mathematics and Computer Science Delft University of Technology The Netherlands, Delft ABSTRACT The need for more intuitive, faster and more effective tools for freeform product design is still an outstanding research issue in shape modeling. We propose a new methodology in which the designer can define optimal shape modification tools for the situation at hand. The key to this method is a dialogue between the designer and the computer, in which the details of the requested shape modifier are settled. The proposed tool, called user-defined modifier (UDM), is based on recent techniques from freeform shape recognition and parameterized, template-controlled shape modification. The dialogue between user and the system is described, and the basic techniques for the UDM tool are presented as well. Keywords Freeform shape design, freeform features, parameterization, reverse design 1. INTRODUCTION In the past decade effective freeform modeling tools have emerged. The creation of freeform product shapes is relatively well supported by current CAID (Computer-Aided Industrial Design) systems, commonly based on a workflow in which surfaces are defined from planar or 3D curves, and surfaces are subsequently synthesized into a shape model. However, any deviation from this forward design paradigm is much less supported, or even unsupported at all, forcing the designer to redo a significant amount of work. A general, effective method for freeform modification is still not available. The main assumption behind the requirements for such method is the ability of the designer to define a shape modification in terms of displacements relative to the current shape. Recent studies have revealed that for the exploration of freeform shape concepts, designers are able to express intended shape modifications in a natural way by putting displacement vectors in the effect region [Coo02a]. The main research challenge of the proposed tool is the trade-off between user requirements and technical requirements. A sophisticated solution to meet the user requirements may imply a high complexity of the model and even a degradation of the model into low-level geometry. Reverse design versus forward design Forward design is a common workflow of design, where a model is built up from low-level elements to features and parts, which are assembled into a product model. If a strict work plan of the design process exists, this workflow will be efficient. However, the workflow is not supportive to freeform shape modeling decisions in any order other than the sequential one prescribed by the workflow. It does support pure synthesizing of shape by combining elements and features, where constraints within and among the features may be defined during the building process. Also Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. WSCG SHORT papers proceedings, ISBN 80-903100 January 31-February 4, 2005 Plzen, Czech Republic. Copyright UNION Agency – Science Press