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空间Coons曲面片正则性判定及其应用

Regularity Determination of Spatial Coons Surface Patches and Its Applications

  • 摘要: Coons曲面片是一种基于边界曲线插值构造光滑二维流形映射的经典方法,广泛应用于计算机图形学、产品外形建模与等几何分析等领域。然而受边界曲线形状复杂、曲率变化剧烈等因素的影响,Coons映射的Jacobian行列式在部分区域可能出现退化甚至符号翻转,映射失去正则性,影响曲面质量与后续分析中的数值稳定性,构建高效、可靠的正则性判定方法对于实现高质量参数化具有重要意义。针对空间Coons曲面片的正则性问题, 提出一系列理论条件与算法。首先基于Jacobian矩阵的秩条件推导出Coons映射正则性的充分判定准则;然后针对Bézier表达形式的Coons曲面,提出一种基于Jacobian行列式Bézier系数的判定方法,将正则性问题转化为系数同号性的约束,提升判定效率与几何可解释性;最后引入Bézier曲面的细分策略,构造出一类正则性的充要条件。所提出的Jacobian系数提取框架可以推广至具有一般拓扑结构的多片B样条曲面,增强了算法的通用性与适应性。数值实验结果表明,对于包含1 752和6 800个双三次Bézier单元的多片B样条曲面片,所提算法可以在0.112 s和0.402 s内完成正则性判定,满足实时工程应用的性能需求。

     

    Abstract: The Coons patch is a classical method for constructing smooth two-dimensional manifold mappings through boundary curve interpolation. It is widely applied in fields such as computer graphics, product shape design, and isogeometric analysis. However, due to factors such as complex boundary curve shapes and significant curvature variations, the Jacobian determinant of a Coons mapping may degenerate or even change sign in certain regions, causing a loss of regularity. This can severely affect the quality of the surface and compromise the numerical stability of subsequent analyses. Developing efficient and reliable methods for regularity verification is of great importance for achieving high-quality parameterizations. To address the regularity verification problem of spatial Coons patches, a series of theoretical conditions and algorithms is proposed. First, based on the condition of the rank of Jacobian matrix, a sufficient criterion for ensuring the regularity of Coons mappings is derived. Second, for Coons patches expressed in Bézier form, a regularity verification method based on the Bézier coefficients of the Jacobian determinant is proposed, transforming the verification task into a set of coefficient sign-consistency constraints, which significantly improves computational efficiency and geometric interpretability. Finally, a subdivision strategy for Bézier surfaces is introduced to construct a class of necessary and sufficient conditions, enabling the global verification problem to be reduced to local subdomain checks. The proposed Jacobian coefficient extraction framework can be extended to multi-patch B-spline surfaces with general topological structures, enhancing the generality and adaptability of the proposed method. Numerical experiment results show that for multi-patch B-spline surfaces consisting of 1 752 and 6 800 bi-cubic Bézier elements, the proposed algorithm completes the regularity verification within 0.112 seconds and 0.402 seconds, respectively, meeting the performance requirements of real-time engineering applications.

     

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