形状可调的C~2连续三次三角Hermite插值样条

基于函数空间{1,sint,cost,sin~2t,sin~3t,cos~3t}构造了一种形状可调的三次三角Hermite插值样条.该样条不仅具有带参数的Hermite型插值样条的主要特性,而且在插值节点为等距时可自动满足C2连续,其形状还可通过所带的参数进行调节.在适当条件下,该样条对应的Ferguson曲线可精确表示工程中一些常见的曲线.     

可调形三次三角Cardinal插值样条曲线

在三次Cardinal插值样条曲线的基础上,引入了三角函数多项式,得到一组带调形参数的三次三角Cardinal样条基函数,以此构造一种可调形的三次三角Cardinal插值样条曲线.该插值样条可以精确表示直线、圆弧、椭圆以及自由曲线,改变调形参数可以调控插值曲线的形状.该插值样条避免了使用有理形式,其表达式较为简洁,计算量也相对较少,从而为多种线段的构造与处理提供了一种通用与简便的方法.     

几种有理插值函数的逼近性质

1　引　　言在曲线和曲面设计中,样条插值是有用的和强有力的工具.不少作者已经研究了很多种类型的样条插值[1,2,3,4].近些年来,有理插值样条,特别是三次有理插值样条,以及它们在外型控制中的应用,已有了不少工作[5,6,7].有理插值样条的表达式中有某些参数,正是由于这些参数,有理插值样条在外型控制中充分显示了它的灵活性;但也正是由于这些参数,使它的逼近性质的研究增加了困难.因此,关于有理插值样条的逼近性质的研究很少见诸文献.本文在第二节首先叙述几种典型的有理插值样条,其中包括分母为一次、二次的三次有理插值样条和仅基于函数值…     

分段三次保形插值法

1 引言 计算机图形学的一个基本问题就是寻找一条光滑曲线过一组型值点{x_i,y_i}(i=0,1,…n+1),解决这一问题最简单的办法是用分段三次Hermite插值,这种插值构造容易,绘图简单. 分段三次Hermite插值的关键是估计型值点处的导数,只要估计出一组导数值,就对应一个分段三次Hermite插值.但在实际应用中,必须考虑插值曲线对型值点组某些特征的继承性,如曲线的保凸性,保形性等. [1—2]研究了分段三次Hermite插值的保单调性.[3]导出了分段三次Hermite插值保形的一个充要条件,这一条件表明并非任何型值点组都存在保形插值.正因为如此,许多文献采用了不同的方法解决保形插值问题.[4—5]用分段有理三次,但计算量增加较大;[6]     

六次PH曲线C~1 Hermite插值

本文讨论六次PH(pythagorean hodograph)曲线的Hermite插值问题.六次PH曲线可以分为两种类型,本文使用参数曲线的复数表示形式,分别给出这两类曲线的构造方法.在给定C1连续的Hermite条件下,需要指定一个自由参数以确定插值曲线,本文进一步阐述这个自由参数的几何意义.由于六次PH曲线是非正则曲线,对于第一类曲线,不易控制奇异点在曲线中的位置;而对于第二类曲线,奇异点可以在构造过程中显式地被指定,因此可以有效地避免其在特定曲线段上的出现.     

奇异积分的广义Hermite插值样条逼近

§1.引言 本文利用广义Hermite插值样条讨论如下形式的奇异积分:的逼近,其中w(t)为权函数,积分理解为Cauchy主值积分. 以带权正交多项式作为逼近工具的奇异积分逼近方法,在实际应用中常会遇到许多困难,如确定权函数相应的正交多项式及其零点、计算过程的不稳定性等.用样条函数作     

基于面积约束的统计直方图曲线拟合

我们提出用分段三次Hermite插值曲线拟合统计直方图的新方法.先根据统计直方图的特点选取Hermite插值曲线在插值点处的导数值和可调整的插值点,然后根据面积约束确定调整值,从而得到拟合曲线.所得拟合曲线与统计直方图有面积相等的约束,并且拟合曲线是C1连续的光滑曲线.所给方法简单、实用.     

一种带参数的有理三次样条函数及其应用

构造了一种带参数的有理三次样条函数,它是标准三次样条函数的推广.选择合适的参数,该样条曲线比标准三次插值曲线更加逼近被插值曲线.参数还能局部调节曲线的形状,这给约束控制带来了方便.研究了该种插值曲线的区域控制问题.给出了将其约束于给定的二次曲线之上、之下或之间的充分条件.文中给出了两个数值例子.     

三次均匀B样条曲线的一种新扩展

构造了一组带形状参数的三次B样条曲线,该曲线与经典三次B样条曲线具有相同的基本性质,且可在不改变控制顶点的情况下,通过改变形状参数的取值实现对曲线形状的调整;选取适当的控制顶点,并对形状参数选取适当的取值,构造的三次λ-B样条曲线可以很好的逼近圆和椭圆;提供了插值于已知数据点的λ-B样条曲线的构造方法;最后,通过图例体现了新方法的有效性.     

C^3连续的保形插值三角样本曲线

本给出了构造保形插值曲线的三角样条方法，即在每两个型值点之间构造两段三次参数三角样条曲线。所构造的插值曲线是局部的，保形的和C^3连续的而且曲线的形状可由参数调节。     

An interpolation method by bivariate cubic splines with <Emphasis Type="Italic">c</Emphasis><Superscript>2</Superscript>-join on type-II triangulars at a rectangular domain

In this paper, an interpolating method for bivariate cubic splines with C ²-join on type-II triangular at a rectangular domain is given, and the approximation degree, interpolating existence and uniqueness of the cubic splines are studied. Supported by NSFC General Projects(60473130).     

AN INTERPOLATION METHOD BY BIVARIATE CUBIC SPLINES WITH C~2 -JOIN ON TYPE-II TRIANGULARS AT A RECTANGULAR DOMAIN

In this paper, an interpolating method for bivariate cubic splines with C2-join on type-II triangular at a rectangular domain is given, and the approximation degree, inter-polating existence and uniqueness of the cubic splines are studied.     

C2 Continuous Quartic Hermite Spline Curves with Shape Parameters

In order to relieve the deficiency of the usual cubic Hermite spline curves, the quartic Hermite spline curves with shape parameters is further studied in this work. The interpolation error and estimator of the quartic Hermite spline curves are given. And the characteristics of the quartic Hermite spline curves are discussed. The quartic Hermite spline curves not only have the same interpolation and conti-nuity properties of the usual cubic Hermite spline curves, but also can achieve local or global shape adjustment and C2 continuity by the shape parameters when the interpolation conditions are fixed.     

Additive Schwarz‐type preconditioners for fourth‐order elliptic problems using Hermite cubic splines

In this note, we construct the additive Schwarz‐type preconditioner for fourth‐order elliptic problems with nested subspaces from Hermite cubic splines. We prove that after the preconditioning, the system is well conditioned. The numerical evidence strongly supports our theoretical result. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2006     

On cubic Hermite coalescence hidden variable fractal interpolation functions

Hermite interpolation is a very important tool in approximation theory and numerical analysis, and provides a popular method for modeling in the area of computer aided geometric design. However, the classical Hermite interpolant is unique for a prescribed data set,and hence lacks freedom for the choice of an interpolating curve, which is a crucial requirement in design environment. Even though there is a rather well developed fractal theory for Hermite interpolation that offers a large flexibility in the choice of interpolants, it also has the shortcoming that the functions that can be well approximated are highly restricted to the class of self-affine functions. The primary objective of this paper is to suggest a C1-cubic Hermite interpolation scheme using a fractal methodology, namely, the coalescence hidden variable fractal interpolation, which works equally well for the approximation of a self-affine and non-self-affine data generating functions. The uniform error bound for the proposed fractal interpolant is established to demonstrate that the convergence properties are similar to that of the classical Hermite interpolant. For the Hermite interpolation problem, if the derivative values are not actually prescribed at the knots, then we assign these values so that the interpolant gains global C2-continuity. Consequently, the procedure culminates with the construction of cubic spline coalescence hidden variable fractal interpolants. Thus, the present article also provides an alternative to the construction of cubic spline coalescence hidden variable fractal interpolation functions through moments proposed by Chand and Kapoor [Fractals, 15(1)(2007), pp. 41-53].     

Cubic Splines with Minimal Norm

Natural cubic interpolatory splines are known to have a minimal L ₂-norm of its second derivative on the C ² (or W ₂ ² ) class of interpolants. We consider cubic splines which minimize some other norms (or functionals) on the class of interpolatory cubic splines only. The cases of classical cubic splines with defect one (interpolation of function values) and of Hermite C ¹ splines (interpolation of function values and first derivatives) with spline knots different from the points of interpolation are discussed.     

基于函数值的有理三次插值样条曲线的区域控制

将插值曲线约束于给定的区域之内是曲线形状控制中的重要问题.构造了一种基于函数值的分母为三次的C~1连续有理三次插值样条.这种有理三次插值样条中含有二个调节参数,因而给约束控制带来了方便.对该种插值曲线的区域控制问题进行了研究,给出了将其约束于给定的折线、二次曲线之上、之下或之间的充分条件.最后给出了数值例子.     

Fitting data using optimal Hermite type cubic interpolating splines

In this work we obtain a new optimal property for cubic interpolating splines of Hermite type applied to data-fitting problems. The existence and uniqueness of the Hermite type cubic spline with minimal quadratic oscillation in average are proved.