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Proceedings of CAD'14, 2014, 195-197
A Heuristic Offsetting Scheme on Catmull-Clark Subdivision Surfaces

Jianzhong Wang, Fuhua Cheng, University of Kentucky

Abstract. In rapid prototyping, a hollowed prototype is preferred and significantly reduces the building time and material consumption in contrast to a solid model. Most rapid prototyping obtains solid thin shell by gradually adding or solidifying materials layer by layer. However this is a non-trivial problem to offset a solid involving finding all self-intersections and filling gaps after raw offsetting. While Catmull-Clark subdivision (CCS) surfaces are widely used in solid modeling, the hollow solid/thin shell problems are not well addressed yet. In this paper, we explore the earlier methods of obtaining thin shell CCS solid and present a new thin CCS thin Solid approach, with this new scheme, one can efficiently avoiding the filling gaps and self-intersections with earlier schemes. The new scheme is heuristic, but inner surface is parametric, such that computation of inner surface is simplified. And with Bezier crust applied, inner surface maintains the mesh structure and continuity of outer surface. The obtained thin shell solid is C2 everywhere except at extraordinary points, where it is C1 continuous. Catmull-Clark subdivision surfaces have been widely used in computer graphics and animation. In contrast to traditional spline schemes, the CCS scheme can handle arbitrary topology and easy to design and implement. In 3D modeling, building a hollowed prototype instead of a solid model is required to reduce the building time and material consumption.

Keywords. Rapid prototyping, hollow out a solid, 3D surface offsetting, Bezier crust, Catmull-Clark subdivision

DOI: 10.14733/cadconfP.2014.195-197