The set of configurations reachable by a shortest path of a fixed
length for a car moving only forward in no more a sphere... (it does not
necessary enclose the starting point)
The shape of the reachable domains has been built (by
C. Nissoux said in French "l'ineffable") from the
synthesis of the shortest paths for Dubins' car.
(see X.N. Bui, P. Souères, J.D. Boissonnat and J.P. Laumond, "The
shortest path synthesis for nonholonomic robots moving forwards", in
IEEE Int. Conf. on Robotics and Automation, 1994).
