Game Development Reference
Velocity controls the direcion and speed. In this case, the smoke will rise with a
speed between 128 and 160 , and will have a subtle random movement to either the
left, right, front, or back.
10. The next thing you want to do is give a random start locaion to the smoke, since
you don't want all of the sprites to start exactly at the same locaion. The default
modules do not allow you to set a random start locaion, so you will have to add a
new module to the Paricle Emiter .