Look up Tcl/TK at
www.scriptics.com.
AC3D's UI is made with this - have a peek in the tcl folder.
To control AC3D from tcl/tk, use the 'ac3d' command e.g.
ac3d select_all
There are no specific docs but you can send an
ac3d list
(e.g. put this in a script file) and get a list of all of AC3D's internal commands along with parameters and a small summary of what the command does.
You can also remote control AC3D via a socket
Post any questions in the developers section.
Andy