I've created a swarm of ants by using the explosive mode in particle playground. I want to have a jedi enter and wipe out the ants with swipes of his lightsaber. I thought I could add a series of masks to the particle playground layer each one taking effect succesively and making the ants in its region transparent. However, my first mask seems to have no effect on the layers alpha channel or the visibility of the ants.
1) Any guess at what I've missed?
2) Any suggestions for a better way to do this? (For example, is there a way to keyframe changes in a persistent property map set to opacity?)