  Given a set of $n$ point robots inside a simple polygon $P$, the task is to
move the robots from their starting positions to their target positions along
their shortest paths, while the mutual visibility of these robots is preserved.
Previous work only considered two robots. In this paper, we present an $O(mn)$
time algorithm, where $m$ is the complexity of the polygon, when all the
starting positions lie on a line segment $S$, all the target positions lie on a
line segment $T$, and $S$ and $T$ do not intersect. We also argue that there is
no polynomial-time algorithm, whose running time depends only on $n$ and $m$,
that uses a single strategy for the case where $S$ and $T$ intersect.
