58 research outputs found
On C2 cubic quasi-interpolating splines and their computation by subdivision via blossoming
We discuss the construction of C2 cubic spline quasi-interpolation schemes defined on a
refined partition. These schemes are reduced in terms of degrees of freedom compared to
those existing in the literature. Namely, we provide a rule for reducing them by imposing
super-smoothing conditions while preserving full smoothness and cubic precision. In
addition, we provide subdivision rules by means of blossoming. The derived rules are
designed to express the B-spline coefficients associated with a finer partition from those
associated with the former one."Maria de Maeztu" Excellence Unit IMAG (University of Granada, Spain) CEX2020-001105-MICIN/AEI/10.13039/501100011033University of Granada
University of Granada/CBU
B-spline-like bases for cubics on the Powell-Sabin 12-split
For spaces of constant, linear, and quadratic splines of maximal smoothness
on the Powell-Sabin 12-split of a triangle, the so-called S-bases were recently
introduced. These are simplex spline bases with B-spline-like properties on the
12-split of a single triangle, which are tied together across triangles in a
B\'ezier-like manner.
In this paper we give a formal definition of an S-basis in terms of certain
basic properties. We proceed to investigate the existence of S-bases for the
aforementioned spaces and additionally the cubic case, resulting in an
exhaustive list. From their nature as simplex splines, we derive simple
differentiation and recurrence formulas to other S-bases. We establish a
Marsden identity that gives rise to various quasi-interpolants and domain
points forming an intuitive control net, in terms of which conditions for
-, -, and -smoothness are derived
A tension approach to controlling the shape of cubic spline surfaces on FVS triangulations
We propose a parametric tensioned version of the FVS macro-element to control the shape of the composite surface and remove artificial oscillations, bumps and other undesired behaviour. In particular, this approach is applied to C1 cubic spline surfaces over a four-directional mesh produced by two-stage scattered data fitting methods
A new approach to deal with C2 cubic splines and its application to super-convergent quasi-interpolation
The authors wish to thank the anonymous referees for their very pertinent and useful comments which helped them to improve the original manuscript. The first and third authors are members of the research group FQM 191 Matematica Aplicada funded by the PAIDI programme of the Junta de Andalucia, Spain. The second author would like to thank the University of Granada, Spain for the financial support for the research stay during which this work was carried out.
Funding for open access charge: Universidad de Granada/CBUAIn this paper, we construct a novel normalized B-spline-like representation for C2-continuous cubic spline space defined
on an initial partition refined by inserting two new points inside each sub-interval. The basis functions are compactly
supported non-negative functions that are geometrically constructed and form a convex partition of unity. With the help of the
control polynomial theory introduced herein, a Marsden identity is derived, from which several families of super-convergent
quasi-interpolation operators are defined.Junta de AndaluciaUniversity of Granada, SpainUniversidad de Granada/CBU
Multivariate Splines and Algebraic Geometry
Multivariate splines are effective tools in numerical analysis and approximation theory. Despite an extensive literature on the subject, there remain open questions in finding their dimension, constructing local bases, and determining their approximation power. Much of what is currently known was developed by numerical analysts, using classical methods, in particular the so-called Bernstein-B´ezier techniques. Due to their many interesting structural properties, splines have become of keen interest to researchers in commutative and homological algebra and algebraic geometry. Unfortunately, these communities have not collaborated much. The purpose of the half-size workshop is to intensify the interaction between the different groups by bringing them together. This could lead to essential breakthroughs on several of the above problems
A geometrically exact isogeometric Kirchhoff plate: Feature‐preserving automatic meshing and C1 rational triangular Bézier spline discretizations
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/144603/1/nme5809.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/144603/2/nme5809_am.pd
Characterization of bivariate hierarchical quartic box splines on a three-directional grid
International audienceWe consider the adaptive refinement of bivariate quartic C 2-smooth box spline spaces on the three-directional (type-I) grid G. The polynomial segments of these box splines belong to a certain subspace of the space of quar-tic polynomials, which will be called the space of special quartics. Given a bounded domain Ω ⊂ R 2 and finite sequence (G ℓ) ℓ=0,...,N of dyadically refined grids, we obtain a hierarchical grid by selecting mutually disjoint cells from all levels such that their union covers the entire domain. Using a suitable selection procedure allows to define a basis spanning the hierarchical box spline space. The paper derives a characterization of this space. Under certain mild assumptions on the hierarchical grid, the hierarchical spline space is shown to contain all C 2-smooth functions whose restrictions to the cells of the hierarchical grid are special quartic polynomials. Thus, in this case we can give an affirmative answer to the completeness questions for the hierarchical box spline basis
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