Random spawn of actors after leaving scene

RRS

I'm sure this is basics, but I am having the hardest time spawning actors randomly... sort of like an asteroids game movement... My actors seem to move in random direction (intended) but once they leave the scene, nothing re-spawns, and it seems like forever before the actor "comes back"

Any ideas on how should I execute this?

thegwill

How are you determining that they have left the scene?