I might be a little late for this but
Thanks to Hurricaaane for this garry’s mod addon its great but render time is a killer also to Maxofs2d for not getting pissed off while teaching me how to use this.
Basicly I can animate a bone in 3DS Max which has an attachment on it which is used as a focus point in garry’smod by this script, very useful for machinima but has very long render times :(, where is Source Filmmaker Valve!!
Get SVN and download his script here
(Note only the SVN build has the attachment tracker)
(Also turn of mult-core rendering in gmod or else this will crash when you tick render mode)