Wavefronts and Light Cones for Kerr Spacetimes
  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. 
Francisco Frutos-Alfaro, Frank Grave, Thomas Mueller, Daria Adis
gr-qc