A Sketch-Based Modelling system using Convolution Surfaces

This paper proposes a user-friendly modelling system that interactively generates 3D organic-like shapes from user drawn sketches. A skeleton, in the form of a graph of branching polylines and polygons, is first extracted from the user’s sketch. The 3D shape is then defined as a convolution surface generated by this skeleton. The skeleton’s resolution is adapted according to the level of detail selected by the user. The subsequent 2D strokes are used to infer new object parts, which are combined with the existing shape using CSG operators. We propose an algorithm for computing a skeleton defined as a connected graph of polylines and polygons. To combine the primitives we propose precise CSG operators for a convolution surfaces blending hierarchy. Our contributions also include the extension of the inverse convolution kernel more efficient than the standard pseudo-Cauchy kernel to variable radii segment skeletons. Our new formulation has the advantage of requiring no optimisation step for fitting the 3D shape to the 2D contours. This yields interactive performances and avoids any nondesired oscillation of the reconstructed surface. As our results show, our system allows non-expert users to generate a wide variety of free form shapes with an easy to use sketch-based interface.