I realize to be albe to tear a softbody you use the refine function after reading through the demo. I see that a ImplicitSphere which is created from the ImplicitFn struct is used in the demo. As far as I can tell it is contructed using the center and radius of the object. I could be wrong though.
I guess what I am trying to get at here is how do you create an ImplicitFn? Does it always have to be a sphere as in the demo or is there some other way to design it to different shapes?