4454 articles – 13148 references  [version française]
 HAL: hal-00573618, version 1
 Symposium on Theoretical Aspects of Computer Science (STACS2011), Dortmund : Allemagne (2011)
 Telling convex from reflex allows to map a polygon
 Jérémie Chalopin 1, Shantanu Das 1
 (2011-03-10)
 We consider the exploration of a simple polygon $\mathcal{P}$ by a robot that moves from vertex to vertex along edges of the visibility graph of $\mathcal{P}$. The visibility graph has a vertex for every vertex of $\mathcal{P}$ and an edge between two vertices if they see each other, i.e.~if the line segment connecting them lies inside $\mathcal{P}$ entirely. While located at a vertex, the robot is capable of ordering the vertices it sees in counter-clockwise order as they appear on the boundary, and for every two such vertices, it can distinguish whether the angle between them is convex ($\leq\pi$) or reflex ($>\pi$). Other than that, distant vertices are indistinguishable to the robot. We assume that an upper bound on the number of vertices is known and show that the robot is always capable of reconstructing the visibility graph of $\mathcal{P}$. We also show that multiple identical, indistinguishable and deterministic such robots can always position themselves such that they mutually see each other, i.e.~such that they form a clique in the visibility graph.
 1: Laboratoire d'informatique Fondamentale de Marseille (LIF) CNRS : UMR6166 – Université de la Méditerranée - Aix-Marseille II – Université de Provence - Aix-Marseille I 2: Eldgenössische Technische Hochschule Zürich (ETH Zürich) ETH Zurich
 Subject : Computer Science/Computational ComplexityComputer Science/Data Structures and Algorithms
 Keyword(s): polygon mapping – map construction – autonomous agent – simple robot – visibility graph reconstruction
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 hal-00573618, version 1 http://hal.archives-ouvertes.fr/hal-00573618 oai:hal.archives-ouvertes.fr:hal-00573618 From: Christoph Dürr <> Submitted on: Saturday, 5 March 2011 00:40:47 Updated on: Sunday, 6 March 2011 17:53:39