How to make particle animation intensify as an empty comes near? I know how to use a driver to, for example, make an object rotate as an empty is brought closer to it. But I am wondering if I can use an empty to amplify the keyframe Y values more the closer it gets. This way I can have a forest of trees swaying gently in the wind but for only the tree particles in close proximity to the "wind" empty the sway will intensify to a heavy rocking motion. I would somehow need to specify minimum and maximum amounts of animation. I have no idea what sort of Python expression I would need for this, or if it's even possible to use a driver to amplify keyframed data. Any help appreciated!
Weights on a lattice.



Armature controlling lattice and lattice controls particles.




Particles can be affected by a lattice.  This might prove to be the least CPU resource consuming.  Lattice can be affected by armature or shape keys et cetera.  Higher UVW specifications may produce more controlled effects.
Particles can be affected by forces attached to an empty.  You can use an effector group to minimize force calculation