Università della Svizzera italiana

New shape control tools for rational Bézier curve design

Ramanantoanina, Andriamahenina ; Hormann, Kai

In: Computer aided geometric design, 2021, vol. 88, p. 11

Bézier curves are indispensable for geometric modelling and computer graphics. They have numerous favourable properties and provide the user with intuitive tools for editing the shape of a parametric polynomial curve. Even more control and flexibility can be achieved by associating a shape parameter with each control point and considering rational Bézier curves, which comes with the...

Università della Svizzera italiana

On the Lebesgue constant of barycentric rational Hermite interpolants at equidistant nodes

Cirillo, Emiliano ; Hormann, Kai

In: Journal of computational and applied mathematics, 2019, vol. 349, p. 292-301

Barycentric rational Floater–Hormann interpolants compare favourably to classical polynomial interpolants in the case of equidistant nodes, because the Lebesgue constant associated with these interpolants grows logarithmically in this setting, in contrast to the exponential growth experienced by polynomials. In the Hermite setting, in which also the first derivatives of the interpolant are...

Université de Fribourg

Barycentric rational interpolation at quasi-equidistant nodes

Hormann, Kai ; Klein, Georges ; De Marchi, Stefano

In: Dolomites Research Notes on Approximation, 2012, vol. 5, no. 1, p. 1-6

A collection of recent papers reveals that linear barycentric rational interpolation with the weights suggested by Floater and Hormann is a good choice for approximating smooth functions, especially when the interpolation nodes are equidistant. In the latter setting, the Lebesgue constant of this rational interpolation process is known to grow only logarithmically with the number of nodes....

Université de Fribourg

On the Lebesgue constant of barycentric rational interpolation at equidistant nodes

Bos, Len ; De Marchi, Stefano ; Hormann, Kai ; Klein, Georges

In: Numerische Mathematik, 2012, vol. 121, p. 461–471

Recent results reveal that the family of barycentric rational interpolants introduced by Floater and Hormann is very well-suited for the approximation of functions as well as their derivatives, integrals and primitives. Especially in the case of equidistant interpolation nodes, these infinitely smooth interpolants offer a much better choice than their polynomial analogue. A natural and important...

Università della Svizzera italiana

Hardware accelerated 3D nesh painting

Schärfig, Randolf ; Hormann, Kai

In: VMV 2010 : Vision, modeling & visualization, 2010, p. 211–218

In this paper we present a new algorithm for interactively painting onto 3D meshes that exploits recent advances of GPU technology. As the user moves a brush over the 3D mesh, its paint pattern is projected onto the 3D geometry at the current viewing angle and copied to the corresponding region in the object’s texture atlas. Both operations are realized on the GPU, with the advantage that all...

Università della Svizzera italiana

Polynomial reproduction for univariate subdivision schemes of any arity

Conti, Costanza ; Hormann, Kai

In this paper we study the ability of convergent subdivision schemes to reproduce polynomials in the sense that for initial data, which is sampled from some polynomial function, the scheme yields the same polynomial in the limit. This property is desirable because the reproduction of polynomials up to some degree d implies that a scheme has approximation order d + 1. We first show that any...

Università della Svizzera italiana

Polynomial reproduction for univariate subdivision schemes of any arity

Conti, Costanza ; Hormann, Kai

In: Journal of approximation theory, 2011, vol. 163, no. 4, p. 413-437

In this paper, we study the ability of convergent subdivision schemes to reproduce polynomials in the sense that for initial data, which is sampled from some polynomial function, the scheme yields the same polynomial in the limit. This property is desirable because the reproduction of polynomials up to some degree d implies that a scheme has approximation order d+1. We first show that any...

Università della Svizzera italiana

Parameterizing subdivision surfaces

He, Lei ; Schaefer, Scott ; Hormann, Kai

In: ACM transactions on graphics, 2010, vol. 29, no. 4, p. 120

We present a method for parameterizing subdivision surfaces in an as-rigid- as-possible fashion. While much work has concentrated on parameterizing polygon meshes, little if any work has focused on subdivision surfaces despite their popularity. We show that polygon parameterization methods produce suboptimal results when applied to subdivision surfaces and describe how these methods may be...

Università della Svizzera italiana

Properties of dual pseudo-splines

Dong, Bin ; Dyn, Nira ; Hormann, Kai

In: Applied and computational harmonic analysis, 2010, vol. 29, no. 1, p. 104-110

Dual pseudo-splines are a new family of refinable functions that generalize both the even degree B-splines and the limit functions of the dual 2n-point subdivision schemes. They were introduced by Dyn et al. [10] as limits of subdivision schemes. In [10], simple algebraic considerations are needed to derive the approximation order of the members of this family. In this paper, we use Fourier...