“MudWalker is a free Plug-in developed by Wayne Robson that allows you to easily send your model, textures or screenshots to other applications with a signle click. MudWalker was tested at Pixar to assure it worked will in production pipelines. It’s free to all freelance artists and companies with less than 5 artists(of any type).”
http://www.cgarena.com/freestuff/tutorials/mudbox/mudwalker-relight/intro.html