breakable walls

Hi

There's a sample here somewhere - http://www.nxogre.org/screens/cake3.avi.

I was wondering if there's a downloadable/playable demo for that instead of just AVI?

I was thinking of using that as a base for breakable walls. (eg, cannons, rockets hitting a wall) How was that implemented? Are those convex hull shapes?

Would it accurately break at the point of collision? or would it break randomly?

I would like to setup a scene, where a player would try to surround his home with walls, and monsters will try to break through by tearing down the walls.

Thanks.

It's just various parts of the walls (cubes or convexes) joined together with fixed joints.