Hi,
I would like to find a way to make models link with each other on specific sides. For example a puzzle can only go together 1 way, I need to be able to take parts that “fit together” attract and parts that dont fit would not attract. I hope I have explained this well enough.
and then what? run an animation/simulation of what might happen with random assemblages of parts, like magnets, and let Blender figure out, based on modes and distances, which parts would float together? If so, you’re gonna be disappointed with off-the -shelf functionality; the answer is nope. You would have to figure it out, model the parts together, animate them blowing apart, and then run the video backwards.
Python might help in figuring out initial speed vectors based on closest attracting objects; post in that forum for possible help.
hmmm what you can do make a bone and parent a piece to that bone and add a IK constraint to that bone. Parent to IK bone the other piece. When you move the bone around the the bone that has the constraint will rotate toward it.
Here is an example file:
http://dominomf.com/smcfiles/kngcalvn_puzzle02.blend
You can also have the bones copy each others location by say %25 percent. Things can get interesting!
Here is an example file:
http://dominomf.com/smcfiles/kngcalvn_puzzle.blend
[edit]
Maybe try some copy rotation constraints!
http://dominomf.com/smcfiles/kngcalvn_puzzle03.blend
http://dominomf.com/smcfiles/kngcalvn_puzzle04.blend
I’m not sure what is the best way to do it, but Have fun experimenting! 
Thanks for all the help I will work on these ideas. I would like to try to be more clear. The idea is I have several hundred truck parts and when you pick the proper piece that you want ex. a set of rims that part would then fit if you asked for the proper bolt pattern and you asked for the proper rim size to fit your truck. What i can’t do is make thousands of models for each possible truck and part so what I want is a way to make parts have a way to encode themselves so these parts would know a fits a-h and other parts would know that they only fit i-z type parts. I have a small 3-d puzzle game that when you try to put the wrong part in the place it is not supposed to go it will not lock together
the puzzle I refer to is
http://www.terragame.com/kpbuy.shtml
holy schlamoley. I used to work for GM, and what you are asking for is called a configurator. That is a huge database and searching/sorting program to match up valid configurations of parts that can go together based on option packages. Not possible in Blender. Look into a database program, such as MySql with a program like php. good luck. Use blender to render images of what the parts look like, and define a MySql image field to hold it.
Not possible ? !!! :eek::eek: Surely you jest ! 
As demonstrated in HarkyMan’s Blender People :
http://blenderartists.org/forum/showthread.php?t=76130
mysql / Blender iinteraciton is quite possible.
“Just” need a “little” Python glue logic to figure out how to retrieve the database info, then put the parts in place 
Mike
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