This paper introduces the simulation system "Impulse". Their system is based on combining two ends of the horizon. On one side, collisions can be used to simulate certain kinds of impact-intensive simulations (like bowling, or a ball hitting a chain of balls). On the other side, other kinds of simulations are more suited for constraints. This includes robot arms for example.

The paper proposes how to use both ends of the spectrum in their simulation. When using collisions for the simulation, we need to detect collisions at each step, sort them in time, and handle each one of them. Sorting means that we can always be assured that anything happening before the time of first collision is true. When using constraint based, we use usual constraint based approaches to do the simulation.

The system switches between the two kinds of simulation based on the kind of interactions detected. The paper has a nice example of the interactions happening when opening a door.

It is not clear to me if this system is really implemented fully, or they just implemented the collision part. Anyway, that's not a major detail.