Distortion Cages

From Hash, Inc. WIKI

[edit] How To Make Distortion Box/Cage

Source describing a character walking through a distortion box.

Create a new Action for your model
in the Action create a new Distortion Box
in the D Box's properties select a "target" bone that is parent to all your model's mesh
edit the CPs of the D-Box to make the squashing you want

drop the Action on your model (previously animated to move around in the chor)
the D Box will normally move with the model, so it must be constrained to a Null in the chor to hold it in one place (a place the model will pass through)

Additional comments:

The only hitch I encountered was when i made an action, I thought all I had to do was to go into distortion mode and I would see a 'select target' option in the properties... it took me a minute to try 'New/Distort'

I believe it is also possible to assign the CPs of D Boxes to bones so you don't have to animate them directly in muscle mode.