I was wondering how easy it was to build and "install" new units into CM, I have played Total Annihilation for the past 3 years and have got into 3rd party unit making 8 months ago.
Since I discovered the hidden treasure that is CM I have been interested in having more units (vehicles) in the game, the Australian Sentinal AC1 in particular.
In Total Annihilation (TA) units were modeled using Rhino3D or other similar 3D modelling programs, then the other parts of the model was added - scripting, build pics, animation .gafs, and other parts necessary to make the model "work".
After this process was done, the models directory with sub-direcs for each script/3D model/pic etc was compressed and compiled into a single (.hpi) file that the game would automatically load when starting.
Doubtless CM and TA use different kinds of 3D engines but seeing as CM is so "moddable" it seems only logical (to me anyways) that 3rd party units would not seem too much trouble.