Ok here is what i have couped up so far. I went trought the forums without finding any good material regardin these topics i am about to discuss here. Nor there was absolute “Cant do it” answer to my problem. More like… “I suppose its possible but not sure how to do it”.

Here is the thing. I am working on tank and specially their treads. (yeah seen all those tons of topics about this thing, but they dont seem to try archieve what i am after).

It feels awful to manually animate speeds of all wheels (sure i used copy rotation ofcourse for set of wheels on both sides of the tank) and make the match with the speed of treads which must match the speed of the speed of tank… :S So many many things to “sync”.

I started to think why one cant take say… from side view the most mids wheel on both sides of tank. Take its velocity (movement distance between current frame and previous frame) on the heading axis of the tank… convert this data to the “Time” value of curvepath used for treads and time of the two main rotatining wheels (the ones where other wheels get their rotations copied).

No doubt it would need some fine tuning because the velocity value might be far off the time “scale”. So we would need somesort of transfer “ratio” for the thing. For the Time IPO we would have linear extrapolation line between 0.0 and 100.0 or what ever seems best “steepnes”. The “velocity” constrain would be directly added to the later vertice of the IPO … somehow like this. IPO2_value = Velocity * ratio : The ratio is there to make sure that the velocity is about right (one of the few things we DO have to set manually).

Now about me. I dont know a jack about python really. :S I have done some C… but thats all. So the design/theory above might be totally impossible, but what i have been given to understand it should be no problem to program such script. Basicly what it needs is following items:

way to count velocity of (object) on the along heading axis (defined axis?) and multiply this with ratio best seen fit by artist and export it to time IPO.
Other tools what might be usefull could be Copy Rotation type of constrain for Time.

Well i’ll leave this to you gurus to judge could it be done. :S I imagine many tank modellers would appreciate having one. Its propably not enought accurate system to sync treads to wheels for 100% realistic shots… but it should be good enought for somewhat distant and messy shots of battalions of tanks going cross country.