Hand-Drawn animation collisions

Hello =]

So me and my friend are beginning to create a game, and he has bought a tablet, and a program to create hand-drawn models and props. He understands this is going to be difficult and arduous, and is ok with it. My question is about collisions. He is using Blender, but i imagine there is no way of automatically creating collisions for an hand drawn import.

Is there - in fact - an easy way of creating collisions. Or what are the possible options?

Thanks guys.