This is the default mode and means that the graphical representation
of the CATISO is added into viewpoints as any other graphical
representation.
CATFurtive
This mode means that the graphical representation of the CATISO
will be considered as furtive and then will be drawn using XOR mode
and will overdraw the scene.
CATBackground
This mode means that the graphical representation of the CATISO
will be drawn before any other graphical representations hold in a given
viewpoint.