  For many purposes, a three-dimensional foliation of spacetime is more
advantageous to understanding its light cone structure. We derive the equations
describing such foliations for the Kerr geometry with non-zero cosmological
constant, and show that they reduce to null hypersurfaces in vacuum (anti-)de
Sitter spacetime in the limit of zero mass. Furthermore, we find that these
null hypersurfaces are free of caustics everywhere for $r>0$. Our construction
has applications in numerical studies of rotating black holes, and in defining
Kruskal coordinates for rotating black holes with non-zero cosmological
constant.
