  The Arbitrary Pattern Formation problem asks for a distributed algorithm that
moves a set of autonomous mobile robots to form any arbitrary pattern given as
input. The robots are assumed to be autonomous, anonymous and identical. They
operate in Look-Compute-Move cycles under an asynchronous scheduler. The robots
do not have access to any global coordinate system. The movement of the robots
is assumed to be rigid, which means that each robot is able to reach its
desired destination without interruption. The existing literature that
investigates this problem, considers robots with unobstructed visibility. This
work considers the problem in the more realistic obstructed visibility model,
where the view of a robot can be obstructed by the presence of other robots.
The robots are assumed to be punctiform and equipped with visible lights that
can assume a constant number of predefined colors. We have studied the problem
in two settings based on the level of consistency among the local coordinate
systems of the robots: two axis agreement (they agree on the direction and
orientation of both coordinate axes) and one axis agreement (they agree on the
direction and orientation of only one coordinate axis). In both settings, we
have provided a full characterization of initial configurations from where any
arbitrary pattern can be formed.
