2009

might want only the bottom vertices to appear to be fully affected by the
physical simulation.
5 On the Soft Selection rollout, turn on Use Soft Selection.
6 Set the Falloff value to specify a smooth falloff from the selected vertices
to the unselected ones.
This is represented visually in the viewport.
7 Now open the reactor modifier and turn on Use Soft Selection.
When you run the animation, your specified falloff will be used to blend
smoothly between the keyframed and simulated vertices.
Constraining Deformable Bodies | 4073