This is a example inspired from the bonus level in Aladin where you play as the monkey Abu and avoid certain enemy objects.
I simply made a layer that acts like a timeline sheet where i maped in certain positions of a sprite that triggers when and from where the enemy sprite shall be spawned from.
I could also imagine this to be used to map the boss behavior wich then triggers when the boss shall move or attack and so on instead of doing the "wait" action.
Or the sonic2 bonus level i believe can be made this way to effect the change of layout animation and rings spawning.
File:
dl.dropbox.com/u/5214903/GM/time%20maped%20directional%20spawning.capx
EDIT:
This file version is a lil fixed so now you need only one spawner sprite to do different spawning depending on its variable value
dl.dropbox.com/u/5214903/GM/time%20maped%20directional%20spawningFix.capx