Abstract: In addition to being a very expressive media, 2D sketches representing the contour of a shape are commonly used as a basis for 3D sketch-based modeling. This paper investigates an alternative to the standard way of creating such sketches: instead of carefully following the contour with a pen and erasing or over-sketching, theuser progressively shapes the contour from a simple input curve, only through intuitive deformation gestures. No menus or sliders are used. This is achieved by providing an automatic selection mechanism between a minimal set of deformation operators, inspired from Michael Leyton's perceptual theory of shapes. The shape representation and the active operator parameters are kept transparent to the user. This enables user to focus on the designand makes the system immediately usable by anybody. We validate this new paradigm through a user study that includes a comparison with standard sketching.