My goal is to make a soft body simulation object connected to 2 rigid body simulation objects so that the scale of the soft body object can be changed to act like a contracting muscle and pull the 2 rigid bodies closer.
It seems that using a copy location constraint would work if I could have one vertex group follow another vertex group.
Another way I can describe what I want to get is like having a soft body goal where 2 ends of the soft body mesh are attached to the vertex group location of 2 rigid body meshes, like a barbell where the bar is made of jello and the 2 weights will fall with dynamics.
All of the videos I've seen on constraints seem to skip over using vertex groups. I'm not sure if there is a different way to do this, maybe with a particle system?. It seems to me the answer is in whether I can do this with constraints or do it at all.