SmoothSketch

We introduce SmoothSketch---a system for inferring plausible 3D free-form shapes from visible-contour sketches. In our system, a user's sketch need not be a simple closed curve as in Igarashi's Teddy 1999, but may have cusps and T-junctions, i.e., endpoints of hidden parts of the contour. We follow a process suggested by Williams 1994 for inferring a smooth solid shape from its visible contours: completion of hidden contours, topological shape reconstruction, and smoothly embedding the shape via relaxation. Our main contribution is a practical method to go from a contour drawing to a fairly smooth surface with that drawing as its visible contour. In doing so, we make several technical contributions: • extending Williams' and Mumford's work Mumford 1994 on figural completion of hidden contours containing T-junctions to contours containing cusps as well, • characterizing a class of visible-contour drawings for which inflation can be proved possible, • finding a topological embedding of the combinatorial surface that Williams creates from the figural completion, and • creating a fairly smooth solid shape by smoothing the topological embedding using a mass-spring system.We handle many kinds of drawings (including objects with holes), and the generated shapes are plausible interpretations of the sketches. The method can be incorporated into any sketch-based free-form modeling interface like Teddy.