共查询到18条相似文献,搜索用时 93 毫秒
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平面三次H-Bézier曲线的形状分析 总被引:6,自引:0,他引:6
本文对平面三次H-Bézier曲线的形状进行分析,讨论其诸如奇点、拐点、局部凸和全局凸的几何特征,得出曲线上含有奇点、拐点和曲线为局部凸或全局凸的用控制多边形边向量相对位置表示的充分必要条件. 相似文献
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本文对平面三次H-Bézier曲线的形状进行分析,讨论其诸如奇点、拐点、局部凸和全局凸的几何特征,得出曲线上含有奇点、拐点和曲线为局部凸或全局凸的用控制多边形边向量相对位置表示的充分必要条件. 相似文献
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关于平面四次Bézier曲线的拐点与奇点 总被引:1,自引:0,他引:1
在计算几何中,已给出了三次Bezier曲线的保凸性的充要条件,并进行了几何解释。本文则是导出形式简洁的拐点和奇点方程并对四次Bezier曲线的拐点和奇点的分布进行讨论。按Bezier曲线的拐点个数进行分类,还得到了四次Bezier曲线有奇点的充分必要条件,并给出几个数值实例,实例说明,不但非凸的单纯特征多角形可以有凸的Bezier曲线段,而且非单纯特征多角形也可以有凸的Bezier曲线段。四次Bezier曲线的奇点和拐点是可以共存的。 相似文献
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外形设计中检验凸曲面的判别条件 总被引:1,自引:0,他引:1
关于判别三维欧氏空间中一张曲面是否为凸曲面的问题,我们曾经给出过一些判别法。而在工程设计上却有这样的一种判别法:沿着直角坐标系的三个坐标轴作一系列的平行平面与坐标轴相垂直,于是得到三组平行平面,在此之外再另取一平面,如果所有这些平面与曲面相截得出的都是凸曲线,那么就认为曲面是凸曲面。 相似文献
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A.Mehaute和F.Utreras(1994)给出了一种平面函数型保凸插值构造光滑曲线的方法(以下简称为M-U方法).本文在利用其方法本质的基础上,给出了一种平面上参数型保凸插值构造光滑曲线的方法,同Mehaute和Utreras的方法一样,这里的方法也有局部性.另外这种方法还可以构造平面上的封闭曲线. 相似文献
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平面点列的自动光顺算法 总被引:2,自引:0,他引:2
本文考虑平面点列的光顺问题并将该问题化成最小能量曲线的构成问题,即在原点列和相应允许误差构成的带状区域内构造一条最小能量曲线并给出一种自动算法.整个光顺过程分成两步,第一步利用凸分析原理在原点列的允许变动范围内除去多余拐点;第二步在保凸的前提下构造插值点列的最小能量曲线并通过对最小能量曲线进行修正而达到对原型值点列进行光顺的目的.光顺结果不仅可以得到一光顺点列,同时还得到了一条插值点列的光顺曲线.该方法可以对分布不均匀甚至有较大转角的点列进行光顺,与已有的方法比起来具有光顺能力强光顺范围广的特点. 相似文献
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平面有理Bzier曲线的几何包络性质 总被引:1,自引:1,他引:0
平面三次有理参数曲线段的形状控制问题,已圆满解决.本文讨论一般平面有理参数曲线的几何性质,给出曲线为凸的充分条件;同时也研究了曲线的包络性质,从几何角度给出平面有理曲线的定义. 相似文献
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Takeshi Sasaki 《Results in Mathematics》1995,27(1-2):129-140
This paper deals with a geometric problem on inflection points and affine vertices for closed curves in an affine flat torus. We show that the least number of inflection points lying on a closed curve that is not homotopic to zero is 2 if the torus is affinely equivalent to a euclidean torus and 0 otherwise. We consider also the number of affine vertices on a strictly convex closed curve on a flat torus. An explicit example of a closed curve with six affine vertices is given. 相似文献
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A planar cubic Bézier curve segment that is a spiral, i.e., its curvature varies monotonically with arc-length, is discussed. Since this curve segment does not have cusps, loops, and inflection points (except for a single inflection point at its beginning), it is suitable for applications such as highway design, in which the clothoid has been traditionally used. Since it is polynomial, it can be conveniently incorporated in CAD systems that are based on B-splines, Bézier curves, or NURBS (nonuniform rational B-splines) and is thus suitable for general curve design applications in which fair curves are important. 相似文献
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The concept of pure gaps of a Weierstrass semigroup at several points of an algebraic curve has been used lately to obtain
codes that have a lower bound for the minimum distance which is greater than the Goppa bound. In this work, we show that the
existence of total inflection points on a smooth plane curve determines the existence of pure gaps in certain Weierstrass
semigroups. We then apply our results to the Hermitian curve and construct codes supported on several points that compare
better to one-point codes from that same curve.
相似文献
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We describe the structure of the asymptotic lines near an inflection point of a Lagrangian surface, proving that in the generic situation it corresponds to two of the three possible cases when the discriminant curve has a cusp singularity. Besides being stable in general, inflection points are proved to exist on a compact Lagrangian surface whenever its Euler characteristic does not vanish. 相似文献
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基于包络理论与拓扑映射的方法对四次带参Ball曲线进行了形状分析,得出了曲线上含有奇点,拐点和曲线为局部凸或全局凸的充分必要条件,这些条件完全由控制多边形和形状参数所决定;并进一步讨论了形状参数对形状分布图的影响及其对曲线形状的调节能力.研究表明,四次带参Ball曲线的形状调控能力要优于四次带参Bezier曲线. 相似文献
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For the cubic trigonometric polynomial curves with a shape parameter (TB curves, for short), the effects of the shape parameter on the TB curve are made clear, the shape features of the TB curve are analyzed. The necessary and sufficient conditions are derived for these curves having single or double inflection points, a loop or a cusp, or be locally or globally convex. The results are summarized in a shape diagram of TB curves, which is useful when using TB curves for curve and surface modeling. Furthermore the influences of shape parameter on the shape diagram and the ability for adjusting the shape of the curve are shown by graph examples, respectively. 相似文献