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Documents authored by Osang, Georg

Document
DOI: 10.4230/LIPIcs.SoCG.2021.27
Computing the Multicover Bifiltration

Authors: René Corbet, Michael Kerber, Michael Lesnick, and Georg Osang

Published in: LIPIcs, Volume 189, 37th International Symposium on Computational Geometry (SoCG 2021)

Abstract
Given a finite set A ⊂ ℝ^d, let Cov_{r,k} denote the set of all points within distance r to at least k points of A. Allowing r and k to vary, we obtain a 2-parameter family of spaces that grow larger when r increases or k decreases, called the multicover bifiltration. Motivated by the problem of computing the homology of this bifiltration, we introduce two closely related combinatorial bifiltrations, one polyhedral and the other simplicial, which are both topologically equivalent to the multicover bifiltration and far smaller than a Čech-based model considered in prior work of Sheehy. Our polyhedral construction is a bifiltration of the rhomboid tiling of Edelsbrunner and Osang, and can be efficiently computed using a variant of an algorithm given by these authors as well. Using an implementation for dimension 2 and 3, we provide experimental results. Our simplicial construction is useful for understanding the polyhedral construction and proving its correctness.
Cite as

René Corbet, Michael Kerber, Michael Lesnick, and Georg Osang. Computing the Multicover Bifiltration. In 37th International Symposium on Computational Geometry (SoCG 2021). Leibniz International Proceedings in Informatics (LIPIcs), Volume 189, pp. 27:1-27:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2021)

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@InProceedings{corbet_et_al:LIPIcs.SoCG.2021.27,
  author =	{Corbet, Ren\'{e} and Kerber, Michael and Lesnick, Michael and Osang, Georg},
  title =	{{Computing the Multicover Bifiltration}},
  booktitle =	{37th International Symposium on Computational Geometry (SoCG 2021)},
  pages =	{27:1--27:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-184-9},
  ISSN =	{1868-8969},
  year =	{2021},
  volume =	{189},
  editor =	{Buchin, Kevin and Colin de Verdi\`{e}re, \'{E}ric},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2021.27},
  URN =		{urn:nbn:de:0030-drops-138260},
  doi =		{10.4230/LIPIcs.SoCG.2021.27},
  annote =	{Keywords: Bifiltrations, nerves, higher-order Delaunay complexes, higher-order Voronoi diagrams, rhomboid tiling, multiparameter persistent homology, denoising}
}
Document
DOI: 10.4230/LIPIcs.ESA.2020.75
Generalizing CGAL Periodic Delaunay Triangulations

Authors: Georg Osang, Mael Rouxel-Labbé, and Monique Teillaud

Published in: LIPIcs, Volume 173, 28th Annual European Symposium on Algorithms (ESA 2020)

Abstract
Even though Delaunay originally introduced his famous triangulations in the case of infinite point sets with translational periodicity, a software that computes such triangulations in the general case is not yet available, to the best of our knowledge. Combining and generalizing previous work, we present a practical algorithm for computing such triangulations. The algorithm has been implemented and experiments show that its performance is as good as the one of the CGAL package, which is restricted to cubic periodicity.
Cite as

Georg Osang, Mael Rouxel-Labbé, and Monique Teillaud. Generalizing CGAL Periodic Delaunay Triangulations. In 28th Annual European Symposium on Algorithms (ESA 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 173, pp. 75:1-75:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{osang_et_al:LIPIcs.ESA.2020.75,
  author =	{Osang, Georg and Rouxel-Labb\'{e}, Mael and Teillaud, Monique},
  title =	{{Generalizing CGAL Periodic Delaunay Triangulations}},
  booktitle =	{28th Annual European Symposium on Algorithms (ESA 2020)},
  pages =	{75:1--75:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-162-7},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{173},
  editor =	{Grandoni, Fabrizio and Herman, Grzegorz and Sanders, Peter},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ESA.2020.75},
  URN =		{urn:nbn:de:0030-drops-129419},
  doi =		{10.4230/LIPIcs.ESA.2020.75},
  annote =	{Keywords: Delaunay triangulation, lattice, algorithm, software, experiments}
}
Document
DOI: 10.4230/LIPIcs.SoCG.2018.34
The Multi-cover Persistence of Euclidean Balls

Authors: Herbert Edelsbrunner and Georg Osang

Published in: LIPIcs, Volume 99, 34th International Symposium on Computational Geometry (SoCG 2018)

Abstract
Given a locally finite X subseteq R^d and a radius r >= 0, the k-fold cover of X and r consists of all points in R^d that have k or more points of X within distance r. We consider two filtrations - one in scale obtained by fixing k and increasing r, and the other in depth obtained by fixing r and decreasing k - and we compute the persistence diagrams of both. While standard methods suffice for the filtration in scale, we need novel geometric and topological concepts for the filtration in depth. In particular, we introduce a rhomboid tiling in R^{d+1} whose horizontal integer slices are the order-k Delaunay mosaics of X, and construct a zigzag module from Delaunay mosaics that is isomorphic to the persistence module of the multi-covers.
Cite as

Herbert Edelsbrunner and Georg Osang. The Multi-cover Persistence of Euclidean Balls. In 34th International Symposium on Computational Geometry (SoCG 2018). Leibniz International Proceedings in Informatics (LIPIcs), Volume 99, pp. 34:1-34:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2018)

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@InProceedings{edelsbrunner_et_al:LIPIcs.SoCG.2018.34,
  author =	{Edelsbrunner, Herbert and Osang, Georg},
  title =	{{The Multi-cover Persistence of Euclidean Balls}},
  booktitle =	{34th International Symposium on Computational Geometry (SoCG 2018)},
  pages =	{34:1--34:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-066-8},
  ISSN =	{1868-8969},
  year =	{2018},
  volume =	{99},
  editor =	{Speckmann, Bettina and T\'{o}th, Csaba D.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2018.34},
  URN =		{urn:nbn:de:0030-drops-87471},
  doi =		{10.4230/LIPIcs.SoCG.2018.34},
  annote =	{Keywords: Delaunay mosaics, hyperplane arrangements, discrete Morse theory, zigzag modules, persistent homology}
}
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