  We investigate the light propagation by means of simulations of wavefronts
and light cones for Kerr spacetimes. Simulations of this kind give us a new
insight to better understand the light propagation in presence of massive
rotating black holes. A relevant result is that wavefronts are back scattered
with winding around the black hole. To generate these visualizations, an
interactive computer program with a graphical user interface, called JWFront,
was written in Java.
