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曲率单调的二次有理h-Bézier曲线

Quadratic rational h-Bézier curve with monotonic curvature

  • 摘要: h-Bézier曲线是一类广义Bézier曲线, 增加正实数权因子后得到的有理h-Bézier曲线可精确表示圆锥曲线. 为了获得具有单调曲率的圆锥曲线段, 本文研究标准型二次有理h-Bézier曲线的曲率分布. 通过讨论二次有理h-Bézier曲线的曲率极值, 得到曲线曲率单调的充要条件. 从几何角度解释, 对于首末控制顶点确定的曲线, 为得到曲率单调的双曲线段和椭圆段, 只需中间控制顶点在曲率单调临界圆上或圆内. 从而, 通过选择合适的中间控制顶点位置、权因子w和形状参数h, 即可构造出曲率单调递减或递增的二次有理h-Bézier曲线. 本文方法包含了曲率单调的二次h-Bézier曲线和二次有理Bézier曲线的构造方法, 并且在曲线造型上更具灵活性.

     

    Abstract: The h-Bézier curve is a kind of generalized Bézier curve. The rational h-Bézier curve obtained by adding a positive real number weight factor can accurately represent the conic section. In order to obtain conic curve segments with monotone curvature, this paper studies the curvature distribution of standard quadratic rational h-Bézier curves. By discussing the curvature extremum of quadratic rational h-Bézier curves, a necessary and sufficient condition for monotonicity of curve curvature is obtained. From the geometric point of view, for the curve with the first and last control vertices determined, in order to obtain hyperbolic segments and elliptic segments with monotonous curvature, only the middle control vertices need to be on or within the curvature critical circle. Thus, by selecting appropriate intermediate control vertex positions, weight factors w, and shape parameter h, a curvature monotonic quadratic rational h-Bézier curve can be constructed. This method includes the construction methods of quadratic h-Bézier curves with monotonic curvature and quadratic rational Bézier curves, and is more flexible in curve modeling.

     

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