Freehand sketches in virtual product development

Hybrid model environments are standard practice in the product development. The paper deals with problems related to engineering in hybrid model environments concerned with the inclusion of conceptual design in CAx concepts. For example, vague and fuzzy product data are depicted in 2-D freehand sketches which are used for the creative search for ideas and the further development of a products's function and layout - the gestaltung. The inclusion of these traditional working aids in the virtual product development is not supported methodologically. As a result, it is not possible to work iteratively with both the freehand sketches and the virtual CAx models. There is a lack of tools capable of transferring the imprecise hand-drawn information to geometric, CAx-compatible data. In this paper, strategies based on image processing technologies and 3-D surface modelling techniques are presented which we use to generate 3-D CAx models from freehand sketches