arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2210.07974math.NAcs.NA
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点-法向细分曲线与曲面

Point-Normal Subdivision Curves and Surfaces

Xunnian Yang

AI总结:

本文提出点-法向细分方案,通过联合细化顶点位置和单位法向,将线性细分推广到非线性,能重现圆、圆柱和球面,保持收敛性与平滑阶,并生成视觉$C^2$曲面,实验验证了其有效性。

摘要:

本文提出将线性细分方案推广为用于曲线和曲面建模的非线性细分方案,其方法是在细化顶点位置的同时,细化顶点处的单位控制法向。在每一轮细分中,新的控制法向通过将线性细分的法向投影到单位圆或单位球面上获得,而新的顶点位置则通过沿新细分法向的方向更新线性细分顶点得到。特别地,每个线性细分顶点的新位置由圆弧或螺旋弧端点的加权平均计算得出,这些弧在一端插值旧顶点处的位置和法向,在另一端插值新细分的法向。所提出的细分方案的主要特点有三个方面:(1)点-法向(PN)细分方案可以利用控制点和控制法向重现圆、圆柱和球面;(2)由收敛线性细分方案推广而来的PN细分方案是收敛的,并且可以具有与线性方案相同的平滑阶;(3)推广生成具有平坦奇异点的$C^2$细分曲面的线性细分方案所得的PN $C^2$细分方案,可以生成在视觉上具有$C^2$光滑性且具有非平坦奇异点的细分曲面。文中给出了实验示例,以展示所提技术在曲线和曲面建模中的有效性。

英文摘要:

This paper proposes to generalize linear subdivision schemes to nonlinear subdivision schemes for curve and surface modeling by refining vertex positions together with refinement of unit control normals at the vertices. For each round of subdivision, new control normals are obtained by projections of linearly subdivided normals onto unit circle or sphere while new vertex positions are obtained by updating linearly subdivided vertices along the directions of the newly subdivided normals. Particularly, the new position of each linearly subdivided vertex is computed by weighted averages of end points of circular or helical arcs that interpolate the positions and normals at the old vertices at one ends and the newly subdivided normal at the other ends. The main features of the proposed subdivision schemes are three folds: (1) The point-normal (PN) subdivision schemes can reproduce circles, circular cylinders and spheres using control points and control normals; (2) PN subdivision schemes generalized from convergent linear subdivision schemes converge and can have the same smoothness orders as the linear schemes; (3) PN $C^2$ subdivision schemes generalizing linear subdivision schemes that generate $C^2$ subdivision surfaces with flat extraordinary points can generate visually $C^2$ subdivision surfaces with non-flat extraordinary points. Experimental examples have been given to show the effectiveness of the proposed techniques for curve and surface modeling.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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