  The regular and chaotic character of orbits is investigated in a 3D potential
describing motion in the central parts of a barred galaxy. This potential is an
extension in the 3D space of a 2D potential based on a family of figure-eight
orbits, which was produced using the theory of the inverse problem. Starting
from the results obtained from the 2D system, we proceed to locate the regions
in the phase space of the 3D potential, producing regular or chaotic orbits. In
order to obtain this we use a new dynamical parameter, the S(c) spectrum, which
proves to be a useful and fast indicator in order to distinguish regular motion
from chaos in 3D potentials. Comparison with other methods for detecting chaos
is also discussed.
