CHARACTERISATION OF RATIONAL AND NURBS DEVELOPABLE SURFACES IN COMPUTER AIDED DESIGN

In this paper we provide a characterisation of rational developable surfaces in terms of the blossoms of the bounding curves and three rational functions Λ,M,v.Properties of developable surfaces are revised in this framework.In particular,a closed algebraic formula for the edge of regression of the surface is obtained in terms of the functions Λ,M,v,which are closely related to the ones that appear in the standard decomposition of the derivative of the parametrisation of one of the bounding curves in terms of the director vector of the rulings and its derivative.It is also shown that all rational developable surfaces can be described as the set of developable surfaces which can be constructed with a constant Λ,M,v.The results are readily extended to rational spline developable surfaces.     

Verifying the Implicitization Formulae for Degree N Rational Bézier Curves

This is a continuation of short communication$^{[1]}$. In [1] a verification of the implicitization equation for degree two rational Bézier curves is presented which does not require the use of resultants. This paper presents these verifications in the general cases, i.e., for degree $n$ rational Bézier curves. Thus some interesting interplay between the structure of the $n×n$ implicitization matrix and the de Casteljau algorithm is revealed.     

B—样条逼近曲线的应用

引进了一种构造曲线的逼近技术，它放松了曲线应包含所有数据点这一严格要求。为了度量一曲线能逼近已给数据多边形的好坏，使用了移动控制点的概念。     

Construction of Bézier Surfaces from Prescribed Boundary

In this paper, we present a method for generating Bézier surfaces from the boundary information based on a general second order functional and a third order functional associated with the triharmonic equation. By solving simple linear equations, the internal control points of the resulting Bézier surface can be obtained as linear combinations of the given boundary control points. This is a generalization of previous works on Plateau-Bézier problem, harmonic, biharmonic and quasi-harmonic Bézier surfaces. Some representative examples show the effectiveness of the presented method.     

Dual Bases for a New Family of Generalized Ball Bases

This paper presents the dual bases for a new family of generalized Ball curves with a position parameter K, which includes the Bezier curve, generalized Said-Ball curve and some intermediate curves. Using the dual bases, the relative Marsden identity, conversion formulas of bases and control points of various curves are obtained.     

A Kind of Multivariate NURBS Surfaces

The purpose of this paper is to construct a kind of multivariate NURBS surfaces by using the bivariate B-splines in the space S1/2(Δmn^(2) and discuss some properties of this kind of NURBS surfaces with multiple knots on the type-2 triangulation.     

The Veronese surface revisited

Recently, the classical Veronese surface reemerged in the context of the application oriented field of Computer Aided Geometric Design due to its interesting relation to rational triangular Bézier surfaces. This motivated the investigation of Veronese varieties presented in this paper. It is shown that the general degree Veronese surface forms a singular subvariety of certain algebraic varieties. This general result is then further examined and extended in the low-degree cases . Received 3 May 2000.