“This tutorial requires 3dsmax 2009 or 2010 and the plugin “Ctrl.Ghost” which allows you to control Irradiance Particles and Importons. Irradiance Particles (IP) and Importons are a hidden feature of Mental Ray 3.6. IP and Importons are similar to other GI techniques like Final Gathering.”
http://www.cgarena.com/freestuff/tutorials/max/importons/irradiance.html