Generating CAD Models from Sketches

The ultimate goal of the application described in this paper is the conversion of two-dimensional sketches into three-dimensional CAD curve and surface models. The first creative step of planning and outlining a conceptual idea in the design often is realized in so-called scribbles (conceptual sketches). Normally, they are scribbled with pencils on sheets and thus only can be used for background information to develop and to build-up the three-dimensional shape model in CAD systems. This means that new "computer" sketches arise which have to be derived from the paper scribbles, demand a particular contour description (e.g. Spline curves) and represent the result of conception (the form and styling content is fixed more or less) more than the conceptual steps themselves. A new method enables the conceptual designer to scan paper scribbles and afterwards convert them into a virtual sketch model. The virtual sketch model includes all the "fuzziness" of the paper scribble and the therein expressed conceptual steps but is automatically represented in a sequence of real B-Spline curves. The conceptual designer can work on the scribble-like resulting two-dimensional geometrical representation and further develop it into the final concept and into the three-diemensional CAD surface model.