http://cg.tutsplus.com/tutorials/autodesk-softimage/create-some-dazzling-particle-effects-using-ice-in-softimage/

Using the graphically based, plug and play programming of ICE, you will create and learn to control the motion of electron clouds around a nucleus. This tutorial covers constraints to motion, how to do vector math, particle trails, creating and reusing ICE compounds, and even some basic ICE particle rendering. If you don’t already, you will come to love the flexibility and power that ICE provides to your simulations.