  In this paper, we study the circle formation problem by multiple autonomous
and homogeneous disc-shaped robots (also known as fat robots). The goal of the
robots is to place themselves on the periphery of a circle. Circle formation
has many real-world applications, such as boundary surveillance. This paper
addresses one variant of such problem { uniform circle formation, where the
robots have to be equidistant apart. The robots operate by executing cycles of
the states wait-look-compute-move. They are oblivious, indistinguishable,
anonymous, and do not communicate via message passing. First, we solve the
uniform circle formation problem while assuming the robots to be transparent.
Next, we address an even weaker model, where the robots are non-transparent and
have limited visibility. We propose novel distributed algorithms to solve these
variants. Our presented algorithms in this paper are proved to be correct and
guarantee to prevent collision and deadlock among the swarm of robots.
