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Based on spline manifolds we introduce and study a mathematical framework for analysis-suitable unstructured B-spline spaces. In this setting the parameter domain has a manifold structure, which allows for the definition of function spaces…

Numerical Analysis · Mathematics 2015-07-31 Giancarlo Sangalli , Thomas Takacs , Rafael Vázquez

This paper presents a shape optimisation system to design the shape of an acoustically-hard object in the three-dimensional open space. Boundary element method (BEM) is suitable to analyse such an exterior field. However, the conventional…

Numerical Analysis · Mathematics 2021-05-11 Toru Takahashi , Daisuke Sato , Hiroshi Isakari , Toshiro Matsumoto

Isogeometric analysis allows to define shape functions of global $C^{1}$ continuity (or of higher continuity) over multi-patch geometries. The construction of such $C^{1}$-smooth isogeometric functions is a non-trivial task and requires…

Numerical Analysis · Mathematics 2017-06-13 Mario Kapl , Giancarlo Sangalli , Thomas Takacs

We transpose an optimal control technique to the image segmentation problem. The idea is to consider image segmentation as a parameter estimation problem. The parameter to estimate is the color of the pixels of the image. We use the…

Numerical Analysis · Mathematics 2011-05-24 Hend Ben Ameur , Guy Chavent , Francois Clément , Pierre Weis

Mapping a shape to some parametric domain is a fundamental tool in graphics and scientific computing. In practice, a map between two shapes is commonly represented by two meshes with same connectivity and different embedding. The standard…

Computational Geometry · Computer Science 2020-12-16 Marco Livesu

One key feature of isogeometric analysis is that it allows smooth shape functions. Indeed, when isogeometric spaces are constructed from $p$-degree splines (and extensions, such as NURBS), they enjoy up to $C^{p-1}$ continuity within each…

Numerical Analysis · Mathematics 2016-05-10 Annabelle Collin , Giancarlo Sangalli , Thomas Takacs

We present a novel isogeometric collocation method for solving the Poisson's and the biharmonic equation over planar bilinearly parameterized multi-patch geometries. The proposed approach relies on the use of a modified construction of the…

Numerical Analysis · Mathematics 2024-11-21 Mario Kapl , Aljaž Kosmač , Vito Vitrih

In this work, we present an efficiently computational approach for designing material micro-structures by means of topology optimization. The central idea relies on using the isogeometric analysis integrated with the parameterized level set…

Computational Engineering, Finance, and Science · Computer Science 2023-07-19 Chuong Nguyen , Xiaoying Zhuang , Ludovic Chamoin , Hung Nguyen-Xuan , Xianzhong Zhao , Timon Rabczuk

We introduce the isogeometric shape optimisation of thin shell structures using subdivision surfaces. Both triangular Loop and quadrilateral Catmull-Clark subdivision schemes are considered for geometry modelling and finite element…

Numerical Analysis · Mathematics 2019-05-21 Kosala Bandara , Fehmi Cirak

We develop a new optimisation technique that combines multiresolution subdivision surfaces for boundary description with immersed finite elements for the discretisation of the primal and adjoint problems of optimisation. Similar to wavelets…

Numerical Analysis · Mathematics 2016-01-20 Kosala Bandara , Thomas Rüberg , Fehmi Cirak

We study the space of $C^1$ isogeometric spline functions defined on trilinearly parameterized multi-patch volumes. Amongst others, we present a general framework for the design of the $C^1$ isogeometric spline space and of an associated…

Numerical Analysis · Mathematics 2021-10-06 Mario Kapl , Vito Vitrih

The fast assembling of stiffness and mass matrices is a key issue in isogeometric analysis, particularly if the spline degree is increased. We present two algorithms based on the idea of sum factorization, one for matrix assembling and one…

Numerical Analysis · Mathematics 2019-06-26 A. Bressan , S. Takacs

We consider geometric multigrid methods for the solution of linear systems arising from isogeometric discretizations of elliptic partial differential equations. For classical finite elements, such methods are well known to be fast solvers…

Numerical Analysis · Mathematics 2017-05-16 Clemens Hofreither , Stefan Takacs , Walter Zulehner

Isogeometric Analysis is a high-order discretization method for boundary value problems that uses a number of degrees of freedom which is as small as for a low-order method. Standard isogeometric discretizations require a global…

Numerical Analysis · Mathematics 2021-03-05 Stefan Takacs

Harmonic maps are important in generating parameterizations for various domains, particularly in two and three dimensions. General extensions of two-dimensional harmonic parameterizations for volumetric parameterizations are known to fail…

Computational Geometry · Computer Science 2025-03-04 Caleb B. Goates , Kendrick M. Shepherd

The matrix formation associated to high-order discretizations is known to be numerically demanding. Based on the existing procedure of interpolation and lookup, we design a multiscale assembly procedure to reduce the exorbitant assembly…

Numerical Analysis · Mathematics 2021-07-21 Thibaut Hirschler , Pablo Antolin , Annalisa Buffa

This work presents a novel framework for spherical mesh parameterization. An efficient angle-preserving spherical parameterization algorithm is introduced, which is based on dynamic Yamabe flow and the conformal welding method with solid…

Graphics · Computer Science 2018-10-23 Saad Nadeem , Zhengyu Su , Wei Zeng , Arie Kaufman , Xianfeng Gu

We construct over a given bilinear multi-patch domain a novel $C^s$-smooth mixed degree and regularity isogeometric spline space, which possesses the degree $p=2s+1$ and regularity $r=s$ in a small neighborhood around the edges and…

Numerical Analysis · Mathematics 2024-07-25 Mario Kapl , Aljaž Kosmač , Vito Vitrih

A volume-preserving parameterization is a bijective mapping that maps a 3-manifold onto a specified canonical domain that preserves the local volume. This paper formulates the computation of ball-shaped volume-preserving parameterizations…

Numerical Analysis · Mathematics 2024-07-30 Shu-Yung Liu , Tsung-Ming Huang , Wen-Wei Lin , Mei-Heng Yueh

An algorithm is proposed for the segmentation of image into multiple levels using mean and standard deviation in the wavelet domain. The procedure provides for variable size segmentation with bigger block size around the mean, and having…