Visibility testing and counting

•Given a set of n disjoint line segments and a segment s, we consider 2 problems.•Visibility testing problem is to check whether a given point p is visible to s.•Visibility counting problem is to count the number of segments visible from p.•We give a new randomized algorithm for VTP and an approxima...

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Vydané v:Information processing letters Ročník 115; číslo 9; s. 649 - 654
Hlavní autori: Alipour, Sharareh, Ghodsi, Mohammad, Zarei, Alireza, Pourreza, Maryam
Médium: Journal Article
Jazyk:English
Vydavateľské údaje: Amsterdam Elsevier B.V 01.09.2015
Elsevier Sequoia S.A
Predmet:
Algorithms
Approximation algorithm
Computational geometry
Computer science
Information processing
Mathematical problems
Quadratic programming
Randomized algorithm
Studies
Test methods
Visibility
Computational geometry
Visibility
Randomized algorithm
Approximation algorithm
ISSN:0020-0190, 1872-6119
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Popis
Shrnutí:•Given a set of n disjoint line segments and a segment s, we consider 2 problems.•Visibility testing problem is to check whether a given point p is visible to s.•Visibility counting problem is to count the number of segments visible from p.•We give a new randomized algorithm for VTP and an approximation algorithm for VCP.•We present our experimental results. For a set of n disjoint line segments S in R2, the visibility testing problem (VTP) is to test whether the query point p sees a query segment s∈S. For this configuration, the visibility counting problem (VCP) is to preprocess S such that the number of visible segments in S from any query point p can be computed quickly. In this paper, we solve VTP in expected logarithmic query time using quadratic preprocessing time and space. Moreover, we propose a (1+δ)-approximation algorithm for VCP using at most quadratic preprocessing time and space. The query time of this method is Oϵ(1δ2n) where Oϵ(f(n))=O(f(n)nϵ) and ϵ>0 is an arbitrary constant number.
Bibliografia:SourceType-Scholarly Journals-1
ObjectType-Feature-1
content type line 14
ISSN:0020-0190
1872-6119
DOI:10.1016/j.ipl.2015.03.009