  Let $V$ be a finite set of vertices in the plane and $S$ be a finite set of
polygonal obstacles, where the vertices of $S$ are in $V$. We show how to
construct a plane $2$-spanner of the visibility graph of $V$ with respect to
$S$. As this graph can have unbounded degree, we modify it in three
easy-to-follow steps, in order to bound the degree to $7$ at the cost of
slightly increasing the spanning ratio to 6.
