Multiple Degree Reduction and Elevation of Bézier Curves Using Jacobi–Bernstein Basis Transformations

In this article, we find the optimal r times degree reduction of Bézier curves with respect to the Jacobi-weighted L ₂-norm on the interval [0, 1]. This method describes a simple and efficient algorithm based on matrix computations. Also, our method includes many previous results for the best approximation with L ₁, L ₂, and L _∞-norms. We give some examples and figures to demonstrate these methods.     

On the conditions for the coincidence of two cubic Bézier curves

In a recent article, Wang et al. [2] derive a necessary and sufficient condition for the coincidence of two cubic Bézier curves with non-collinear control points. The condition reads that their control points must be either coincident or in reverse order. We point out that this uniqueness of the control points for polynomial cubics is a straightforward consequence of a previous and more general result of Barry and Patterson, namely the uniqueness of the control points for rational Bézier curves. Moreover, this uniqueness applies to properly parameterized polynomial curves of arbitrary degree.     

On the Structure of Bézier Nets

The distance between two neighbouring multivariate Bézier nets is proved to be $O(m^{-2})$ in this paper. As a consequence, the sequence of Bézier nets is uniformly convergent with the optimal approximation order $O(m^{-1})$. Furthermore, the structures of Bézier nets are explored by investigating how the piecewise linear surface tends to the Bézier surface of $C^{\infty}$.     

Kempe’s Universality Theorem for Rational Space Curves

We prove that every bounded rational space curve of degree d and circularity c can be drawn by a linkage with \( \frac{9}{2} d-6c+1\) revolute joints. Our proof is based on two ingredients. The first one is the factorization theory of motion polynomials. The second one is the construction of a motion polynomial of minimum degree with given orbit. Our proof also gives the explicit construction of the linkage.     

Direction monotonicity for a rational Bézier curve

The monotonicity of a rational Bézier curve, usually related to an explicit function,is determined by the used coordinate system. However, the shape of the curve is independent of the coordinate system. To meet the affine invariant property, a kind of generalized monotonicity, called direction monotonicity, is introduced for rational Bézier curves. The direction monotonicity is applied to both planar and space curves and to both Cartesian and affine coordinate systems, and it includes the traditional monotonicity as a subcase. By means of it,proper affine coordinate systems may be chosen to make some rational Bézier curves monotonic.Direction monotonic interpolation may be realized for some of the traditionally nonmonotonic data as well.     

有理Bézier函数

本文研究了有理Bézier函数与有理Bézier曲线的关系,提出了诱导控制多边形的概念,籍助于它从几何观点出发,研究了有理函数Bézier的一些性质。     

Bézier曲面拟合

A method of fitting data points with piecewise least square is provided for thecomputer aided geometric design. It contains fitting of Bezier curves, fitting ofBezier surfaces and constrained fitting of surfaces. This method has been put into usein the design system for automobile surfaces.     

A Construction of the Rational Function Sheaves on Elliptic Curves

Abstract The authors introduce an effective method to construct the rational function sheaf κ on an elliptic curve E, and further study the relationship between κ and any coherent sheaf on E. Finally, it is shown that the category of all coherent sheaves of finite length on E is completely characterized by κ.     

三角Bézier曲面和四边Bézier曲面之间的相互转化

Bézier曲面有两种不同的形式：三角Bézier曲面和四边Bézier曲面,它们有着不同的基底和不同的几何拓扑结构,但是它们也有很多共同的性质,因此三角Bézier曲面和四边Bézier曲面之间的相互转化就成为CAGD里一个重要研究课题．在本文中,我们用函数复合的方法实现两者之间的相互转化．被复合的两个函数,一个用Polar形式表示,另一个用常见的Bernstein基形式表示．     

点集Bézier曲线

提出了点集Bézier曲线的概念,给出了点集Bézier曲线的性质及细分算法.按照点集算术的定义,当点集是长方形闭域或圆盘时,点集Bézier曲线就是区间Bézier曲线或圆盘Bézier曲线,因此,点集Bézier曲线是对区间Bézier曲线和圆盘Bézier曲线的推广.     

A new type of the generalized Bézier curves

In this paper, we improve the generalized Bernstein basis functions introduced by Han, et al. The new basis functions not only inherit the most properties of the classical Bernstein basis functions, but also reserve the shape parameters that are similar to the shape parameters of the generalized Bernstein basis functions. The degree elevation algorithm and the conversion formulae between the new basis functions and the classical Bernstein basis functions are obtained. Also the new Q-Bézier curve and surface...     

Bounding Pyramids and Bounding Cones for Triangular Bézier Surfaces

This paper describes practical approaches on how to construct bounding pyramids and bounding cones for triangular Bézier surfaces. Examples are provided to illustrate the process of construction and comparison is made between various surface bounding volumes. Furthermore, as a starting point for the construction, we provide a way to compute hodographs of triangular Bézier surfaces and improve the algorithm for computing the bounding cone of a set of vectors.     

Degree reduction of SG-Bézier surfaces based on grey wolf optimizer

Aiming at the problem of approximate degree reduction of SG-Bézier surfaces, a method is proposed to achieve the degree reduction from (n × n) to (m × m) (m < n). Starting from the idea of grey wolf optimizer (GWO) algorithm and combining the geometric properties of SG-Bézier surfaces, this method transforms the degree reduction problem of SG-Bézier surfaces into an optimization problem. By choosing the fitness function, the degree reduction approximation of shape-adjustable SG-Bézier surfaces under unconstrained and angular interpolation constraints is realized. At the same time, some concrete examples of degree reduction and its errors are given. The results show that this method not only achieves good degree reduction effect but also is easy to implement and has high precision.     

区间Bézier曲线的边界

本文证明了ｎ次区间Ｂéｚｉｅｒ曲线的边界必由分段ｎ次Ｂéｚｉｅｒ曲线与平行于坐标轴的直线段构成，并具体给出了２次和３次区间Ｂéｚｉｅｒ曲线的边界表示．     

指数平均Bézier曲线族

利用指数平均族与Béier曲线结合定义了指数平均Bézier曲线族.首先研究了指数平均族,阐述了指数平均族的单调性和正规性,其次由Bernstein函数定义得到n次s阶指数平均Bernstein函数,讨论了它与函数f之间的关系,最后,研究指数平均Bézier曲线族的性质,讨论了它的升阶,de casteljan算法,分割定理等.     

Bézier variant of Baskakov-Beta-Stancu operators

In the year 1994, Gupta (Approx Theory Appl (N.S.) 10(3):74–78, 1994) introduced the integral modification of well known Baskakov operators with weights of Beta basis functions and obtained better approximation over the usual Baskakov Durrmeyer operators. The rate of convergence for Bézier variant of these operators for functions of bounded variations were discussed in Gupta (Int J Math Math Sci 32(8):471–479, 2002). The present paper is the extension of the previous work, here we consider the Bézier variant of Baskakov-Beta-Stancu operators. We estimate the rate of convergence of these operators for the bounded functions. In the end of the paper we suggest an open problem.     

On the formulation of a BEM in the Bézier–Bernstein space for the solution of Helmholtz equation

This paper proposes a novel boundary element approach formulated on the Bézier-Bernstein basis to yield a geometry-independent field approximation. The proposed method is geometrically based on both computer aid design (CAD) and isogeometric analysis (IGA), but field variables are independently approximated from the geometry. This approach allows the appropriate approximation functions for the geometry and variable field to be chosen. We use the Bézier–Bernstein form of a polynomial as an approximation basis to represent both geometry and field variables. The solution of the element interpolation problem in the Bézier–Bernstein space defines generalised Lagrange interpolation functions that are used as element shape functions. The resulting Bernstein–Vandermonde matrix related to the Bézier–Bernstein interpolation problem is inverted using the Newton-Bernstein algorithm. The applicability of the proposed method is demonstrated solving the Helmholtz equation over an unbounded region in a two-and-a-half dimensional (2.5D) domain.     

Degree elevation from Bzier curve to C-Bzier curve with corner cutting form

The existing results of curve degree elevation mainly focus on the degree of algebraic polynomials. The paper considers the elevation of degree of the trigonometric polynomial, from a Bzier curve on the algebraic polynomial space, to a C-B′ezier curve on the algebraic and trigonometric polynomial space. The matrix of degree elevation is obtained by an operator presentation and a derivation pyramid. It possesses not a recursive presentation but a direct expression. The degree elevation process can also be represented as a corner cutting form.     

Approximating the Fréchet Distance for Realistic Curves in Near Linear Time

We present a simple and practical (1+ε)-approximation algorithm for the Fréchet distance between two polygonal curves in ? ^d . To analyze this algorithm we introduce a new realistic family of curves, c-packed curves, that is closed under simplification. We believe the notion of c-packed curves to be of independent interest. We show that our algorithm has near linear running time for c-packed polygonal curves, and similar results for other input models, such as low-density polygonal curves.     

有理Bézier曲线hybrid逼近收敛性

hybrid逼近算法是一种用多项式逼近有理多项式的有效方法,但是这种算法逼近有时会发散.这样讨论它的收敛性条件就变得弥足重要.在前人工作的基础上研究了重新参数化对有理Bézier曲线hybrid逼近收敛性的影响,在权系数的某些假定下,得到了重新参数化后hybrid逼近收敛的充分条件.