[jitter] constrain matrix to boundaries

Your best bet will be to convert the matrix to polar coordinates, apply 
your clamp or modulo function on the amplitude, and then convert back to 
cartesian coords.  Jit.expr should be your best bet with that.

I don't have time to come up with an example, but I think there have 
already been some cartopol/poltocar jit.expr examples posted.

Best of luck,
Andrew B.