Polar NURBS Surface with Curvature Continuity

Authors

  • K.-L. Shi,

    1. Inria, Villers-lès-Nancy, France
    2. Key Laboratory for Information System Security, Ministry of Education of China, Beijing, China
    3. Tsinghua National Laboratory for Information Science and Technology, Beijing, China
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  • J.-H. Yong,

    1. School of Software, Tsinghua University, Beijing, China
    2. Key Laboratory for Information System Security, Ministry of Education of China, Beijing, China
    3. Tsinghua National Laboratory for Information Science and Technology, Beijing, China
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  • L. Tang,

    1. School of Software, Tsinghua University, Beijing, China
    2. Key Laboratory for Information System Security, Ministry of Education of China, Beijing, China
    3. Tsinghua National Laboratory for Information Science and Technology, Beijing, China
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  • J.-G. Sun,

    1. School of Software, Tsinghua University, Beijing, China
    2. Key Laboratory for Information System Security, Ministry of Education of China, Beijing, China
    3. Tsinghua National Laboratory for Information Science and Technology, Beijing, China
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  • J.-C. Paul

    1. Inria, Villers-lès-Nancy, France
    2. School of Software, Tsinghua University, Beijing, China
    3. Key Laboratory for Information System Security, Ministry of Education of China, Beijing, China
    4. Tsinghua National Laboratory for Information Science and Technology, Beijing, China
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  • The research was partly supported by Chinese 973 Program (2010CB328001) and Chinese 863 Program (2012AA040902). The second author was supported by the NSFC (61035002, 61272235). The fifth author was supported by the NSFC (61063029, 61173077).

Abstract

Polar NURBS surface is a kind of periodic NURBS surface, one boundary of which shrinks to a degenerate polar point. The specific topology of its control-point mesh offers the ability to represent a cap-like surface, which is common in geometric modeling. However, there is a critical and challenging problem that hinders its application: curvature continuity at the extraordinary singular pole. We first propose a sufficient and necessary condition of curvature continuity at the pole. Then, we present constructive methods for the two key problems respectively: how to construct a polar NURBS surface with curvature continuity and how to reform an ordinary polar NURBS surface to curvature continuous. The algorithms only depend on the symbolic representation and operations of NURBS, and they introduce no restrictions on the degree or the knot vectors. Examples and comparisons demonstrate the applications of the curvature-continuous polar NURBS surface in hole-filling and free-shape modeling.

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