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Given a convex polygon of $n$ sides, one can draw $n$ disks (called side disks) where each disk has a different side of the polygon as diameter and the midpoint of the side as its center. The intersection graph of such disks is the…

Metric Geometry · Mathematics 2016-06-17 Clemens Huemer , Pablo Pérez-Lantero

Motivated by a result of [1] which states that if F is a subgraph of a convex complete graph K_n and F contains no boundary edge of K_n and |E(F)| \leq n-3, then K_n - F admits a triangulation, we determine necessary and sufficient…

Combinatorics · Mathematics 2016-11-29 Niran Abbas Ali , Gek L. Chia , Hazim Michman Trao , Adem Kilicman

We consider straight-line outerplanar drawings of outerplanar graphs in which a small number of distinct edge slopes are used, that is, the segments representing edges are parallel to a small number of directions. We prove that $\Delta-1$…

Computational Geometry · Computer Science 2014-04-11 Kolja Knauer , Piotr Micek , Bartosz Walczak

A polyhedral surface~$\mathcal{C}$ in $\mathbb{R}^3$ with convex polygons as faces is a side-contact representation of a graph~$G$ if there is a bijection between the vertices of $G$ and the faces of~$\mathcal{C}$ such that the polygons of…

Computational Geometry · Computer Science 2023-08-02 André Schulz

A planar orthogonal drawing of a planar 4-graph G (i.e., a planar graph with vertex-degree at most four) is a crossing-free drawing that maps each vertex of G to a distinct point of the plane and each edge of $G$ to a sequence of horizontal…

Computational Geometry · Computer Science 2022-05-17 Walter Didimo , Michael Kaufmann , Giuseppe Liotta , Giacomo Ortali

A rectangular drawing of a planar graph $G$ is a planar drawing of $G$ in which vertices are mapped to grid points, edges are mapped to horizontal and vertical straight-line segments, and faces are drawn as rectangles. Sometimes this latter…

Computational Geometry · Computer Science 2024-07-25 Carlos Alegria , Giordano Da Lozzo , Giuseppe Di Battista , Fabrizio Frati , Fabrizio Grosso , Maurizio Patrignani

Computing planar orthogonal drawings with the minimum number of bends is one of the most relevant topics in Graph Drawing. The problem is known to be NP-hard, even when we want to test the existence of a rectilinear planar drawing, i.e., an…

Computational Geometry · Computer Science 2023-09-07 Emilio Di Giacomo , Walter Didimo , Giuseppe Liotta , Fabrizio Montecchiani , Giacomo Ortali

We show that a transitively reduced digraph has a confluent upward drawing if and only if its reachability relation has order dimension at most two. In this case, we construct a confluent upward drawing with $O(n^2)$ features, in an $O(n)…

Computational Geometry · Computer Science 2015-07-16 David Eppstein , Joseph A. Simons

We show that any outerplanar graph admits a planar straightline drawing such that the length ratio of the longest to the shortest edges is strictly less than 2. This result is tight in the sense that for any $\epsilon > 0$ there are…

Computational Geometry · Computer Science 2017-09-04 Sylvain Lazard , William Lenhart , Giuseppe Liotta

Recently, there has been interest in representing single graphs by multiple drawings; for example, using graph stories, storyplans, or uncrossed collections. In this paper, we apply this idea to orthogonal graph drawing. Due to the…

A drawing of a graph is said to be a {\em straight-line drawing} if the vertices of $G$ are represented by distinct points in the plane and every edge is represented by a straight-line segment connecting the corresponding pair of vertices…

Combinatorics · Mathematics 2012-03-08 V S Padmini Mukkamala

We prove that any planar graph on $n$ vertices has less than $O(5{.}2852^n)$ spanning trees. Under the restriction that the planar graph is 3-connected and contains no triangle and no quadrilateral the number of its spanning trees is less…

Combinatorics · Mathematics 2010-09-07 Kevin Buchin , André Schulz

A graph with n vertices is 1-planar if it can be drawn in the plane such that each edge is crossed at most once, and is optimal if it has the maximum of 4n-8 edges. We show that optimal 1-planar graphs can be recognized in linear time. Our…

Discrete Mathematics · Computer Science 2018-01-25 Franz J. Brandenburg

In this work, we introduce and develop a theory of convex drawings of the complete graph $K_n$ in the sphere. A drawing $D$ of $K_n$ is convex if, for every 3-cycle $T$ of $K_n$, there is a closed disc $\Delta_T$ bounded by $D[T]$ such…

Combinatorics · Mathematics 2022-09-16 Alan Arroyo , Dan McQuillan , R. Bruce Richter , Gelasio Salazar

Given a planar graph $G$, we consider drawings of $G$ in the plane where edges are represented by straight line segments (which possibly intersect). Such a drawing is specified by an injective embedding $\pi$ of the vertex set of $G$ into…

Discrete Mathematics · Computer Science 2011-05-20 Mihyun Kang , Oleg Pikhurko , Alexander Ravsky , Mathias Schacht , Oleg Verbitsky

Computing the number of realizations of a minimally rigid graph is a notoriously difficult problem. Towards this goal, for graphs that are minimally rigid in the plane, we take advantage of a recently published algorithm, which is the…

Combinatorics · Mathematics 2018-04-12 Georg Grasegger , Christoph Koutschan , Elias Tsigaridas

A graph is rectilinear planar if it admits a planar orthogonal drawing without bends. While testing rectilinear planarity is NP-hard in general (Garg and Tamassia, 2001), it is a long-standing open problem to establish a tight upper bound…

Data Structures and Algorithms · Computer Science 2023-06-23 Walter Didimo , Michael Kaufmann , Giuseppe Liotta , Giacomo Ortali

We define strict confluent drawing, a form of confluent drawing in which the existence of an edge is indicated by the presence of a smooth path through a system of arcs and junctions (without crossings), and in which such a path, if it…

Computational Geometry · Computer Science 2016-08-12 David Eppstein , Danny Holten , Maarten Löffler , Martin Nöllenburg , Bettina Speckmann , Kevin Verbeek

A planar orthogonal drawing $\Gamma$ of a planar graph $G$ is a geometric representation of $G$ such that the vertices are drawn as distinct points of the plane, the edges are drawn as chains of horizontal and vertical segments, and no two…

Data Structures and Algorithms · Computer Science 2019-10-28 Walter Didimo , Giuseppe Liotta , Giacomo Ortali , Maurizio Patrignani

A natural way to represent on the plane both a planar graph and its dual is to follow the definition of the dual, thus, to place vertices inside their corresponding primal faces, and to draw the dual edges so that they only cross their…

Computational Geometry · Computer Science 2015-05-12 Tamara Mchedlidze