I've added a Chimera extension called Morph Map http://www.cgl.ucsf.edu/chimera/experimental/morph_map/morphmap.html to the experimental features web page: http://www.cgl.ucsf.edu/chimera/experimental/experimental.html It interpolates between two volume data sets and makes animations. The original version of this tool was written by Wei Zhang in Pawel Penczek's lab. Tom