Let's say you have two circles, and you want to fill only the non-intersecting sections of these circles. Listing 2 shows how you can do that.

Gears on nonparallel, non-intersecting shafts also have pitch circles, but the rolling-pitch-circle concept is not valid.

The non-intersecting trails of the "agents" are eventually materialized into non-linear aluminum stripes, of length equivalent to the "agents"' lives.