Else i have seen your videos...

Something else who is not 3D but can be useful with some object created by Moi for animate them!

The very funny free and versatile Algodoo... http://www.algodoo.com
Perfect for all public !:)

The grey legs have motors that turn in the opposite direction.
The "rotating" rectangle will hit the legs.

All are in contact A, touching but not blocking!

The deformed rounding is the result of the ladder tool on a round-ended segment

The result is a jumping movement of the legs of the "crutch"! :)

Here all is drawn inside Algodoo but as you can import any images you can put any images of MOi's Objects ! ;)