On approximations to minimum link visibility paths in simple polygons

Abstract

We investigate a practical variant of the well-known polygonal visibility path (watchman) problem. For a polygon $P$, a minimum link visibility path is a polygonal visibility path in $P$ that has the minimum number of links. The problem of finding a minimum link visibility path is NP-hard for simple polygons. If the link-length (number of links) of a minimum link visibility path (tour) is $Opt$ for a simple polygon $P$ with $n$ vertices, we provide an algorithm with $O(k{n}^2)$ runtime that produces polygonal visibility paths (or tours) of link-length at most $(\gamma +a_l/(k-1))Opt$ (or $(\gamma +a_l/k)Opt$), where $k$ is a parameter dependent on $P$, $a_l$ is an output sensitive parameter and $\gamma$ is the approximation factor of an $O(k^3)$ time approximation algorithm for the graphic traveling salesman problem (path or tour version).