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Documents authored by Palfrader, Peter

Document
DOI: 10.4230/LIPIcs.SoCG.2020.38
On Implementing Straight Skeletons: Challenges and Experiences

Authors: Günther Eder, Martin Held, and Peter Palfrader

Published in: LIPIcs, Volume 164, 36th International Symposium on Computational Geometry (SoCG 2020)

Abstract
We present Cgal implementations of two algorithms for computing straight skeletons in the plane, based on exact arithmetic. One code, named Surfer2, can handle multiplicatively weighted planar straight-line graphs (PSLGs) while our second code, Monos, is specifically targeted at monotone polygons. Both codes are available on GitHub. We discuss algorithmic as well as implementational and engineering details of both codes. Furthermore, we present the results of an extensive performance evaluation in which we compared Surfer2 and Monos to the straight-skeleton package included in Cgal. It is not surprising that our special-purpose code Monos outperforms Cgal’s straight-skeleton implementation. But our tests provide ample evidence that also Surfer2 can be expected to be faster and to consume significantly less memory than the Cgal code. And, of course, Surfer2 is more versatile because it can handle multiplicative weights and general PSLGs as input. Thus, Surfer2 currently is the fastest and most general straight-skeleton code available.
Cite as

Günther Eder, Martin Held, and Peter Palfrader. On Implementing Straight Skeletons: Challenges and Experiences. In 36th International Symposium on Computational Geometry (SoCG 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 164, pp. 38:1-38:17, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{eder_et_al:LIPIcs.SoCG.2020.38,
  author =	{Eder, G\"{u}nther and Held, Martin and Palfrader, Peter},
  title =	{{On Implementing Straight Skeletons: Challenges and Experiences}},
  booktitle =	{36th International Symposium on Computational Geometry (SoCG 2020)},
  pages =	{38:1--38:17},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-143-6},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{164},
  editor =	{Cabello, Sergio and Chen, Danny Z.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2020.38},
  URN =		{urn:nbn:de:0030-drops-121964},
  doi =		{10.4230/LIPIcs.SoCG.2020.38},
  annote =	{Keywords: weighted straight skeleton, implementation, algorithm engineering, experiments, Cgal, Core}
}
Document
Media Exposition
DOI: 10.4230/LIPIcs.SoCG.2020.76
Step-By-Step Straight Skeletons (Media Exposition)

Authors: Günther Eder, Martin Held, and Peter Palfrader

Published in: LIPIcs, Volume 164, 36th International Symposium on Computational Geometry (SoCG 2020)

Abstract
We present two software packages for computing straight skeletons: Monos, our implementation of an algorithm by Biedl et al. (2015), computes the straight skeleton of a monotone input polygon, and Surfer2 implements a generalization of an algorithm by Aichholzer and Aurenhammer (1998) to handle multiplicatively-weighted planar straight-line graphs as input. The graphical user interfaces that ship with our codes support step-by-step computations, where each event can be investigated and studied by the user. This makes them a canonical candidate for educational purposes and detailed event analyses. Both codes are freely available on GitHub.
Cite as

Günther Eder, Martin Held, and Peter Palfrader. Step-By-Step Straight Skeletons (Media Exposition). In 36th International Symposium on Computational Geometry (SoCG 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 164, pp. 76:1-76:4, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{eder_et_al:LIPIcs.SoCG.2020.76,
  author =	{Eder, G\"{u}nther and Held, Martin and Palfrader, Peter},
  title =	{{Step-By-Step Straight Skeletons}},
  booktitle =	{36th International Symposium on Computational Geometry (SoCG 2020)},
  pages =	{76:1--76:4},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-143-6},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{164},
  editor =	{Cabello, Sergio and Chen, Danny Z.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2020.76},
  URN =		{urn:nbn:de:0030-drops-122343},
  doi =		{10.4230/LIPIcs.SoCG.2020.76},
  annote =	{Keywords: weighted straight skeleton, implementation, visualization, graphical user interface, education}
}
Document
CG Challenge
DOI: 10.4230/LIPIcs.SoCG.2020.85
Computing Low-Cost Convex Partitions for Planar Point Sets Based on Tailored Decompositions (CG Challenge)

Authors: Günther Eder, Martin Held, Stefan de Lorenzo, and Peter Palfrader

Published in: LIPIcs, Volume 164, 36th International Symposium on Computational Geometry (SoCG 2020)

Abstract
Our work on minimum convex decompositions is based on two key components: (1) different strategies for computing initial decompositions, partly adapted to the characteristics of the input data, and (2) local optimizations for reducing the number of convex faces of a decomposition. We discuss our main heuristics and show how they helped to reduce the face count.
Cite as

Günther Eder, Martin Held, Stefan de Lorenzo, and Peter Palfrader. Computing Low-Cost Convex Partitions for Planar Point Sets Based on Tailored Decompositions (CG Challenge). In 36th International Symposium on Computational Geometry (SoCG 2020). Leibniz International Proceedings in Informatics (LIPIcs), Volume 164, pp. 85:1-85:11, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2020)

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@InProceedings{eder_et_al:LIPIcs.SoCG.2020.85,
  author =	{Eder, G\"{u}nther and Held, Martin and de Lorenzo, Stefan and Palfrader, Peter},
  title =	{{Computing Low-Cost Convex Partitions for Planar Point Sets Based on Tailored Decompositions}},
  booktitle =	{36th International Symposium on Computational Geometry (SoCG 2020)},
  pages =	{85:1--85:11},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-143-6},
  ISSN =	{1868-8969},
  year =	{2020},
  volume =	{164},
  editor =	{Cabello, Sergio and Chen, Danny Z.},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.SoCG.2020.85},
  URN =		{urn:nbn:de:0030-drops-122438},
  doi =		{10.4230/LIPIcs.SoCG.2020.85},
  annote =	{Keywords: Computational Geometry, geometric optimization, algorithm engineering, convex decomposition}
}
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