particleSystem Example : Snow

The emitter is a plane overhead; there are no forces, but the initial direction is set to make the particles move downward.
/* particleSystem Example 3: Snow */

light ()

particleSystem (
	emitterVolume(box -5 0 10 5 10 10),
	initialDirection(0 0 -1),
	speed (1),
	rotation (-15 -15 -15 15 15 15),
	size (.1 .3),
	emitterRate(3),
	lifespan(10),
	count(100)
)

(c) Ben Chang