They said that SPH is supposed to do what you two speak of.
It turns bodies in US^2 into "fluid-like" bodies that effect each other, gravitationally.
So, when two of these fluid bodies pass close by each other, you would see the bodies being stretched into an oblong sphere and maybe see some particles fly off one, or both bodies, onto the other body or into space.
I think Greenleaf posted a video on youtube showing US^2 with this SPH system.
You two should check it out.