Particle System Life Span

Setting Particles to grow older in the Particle Panel causes the particles to stop. Setting the flag manually in code seems to do nothing. What does this flag do?

So apparently there is a particle interval that does this… I suppose I can use that. Does it clean itself up? Can I use multiple ones? I guess I’ll find out.

Particle intervals appear to destroy the particles entirely. Is this the best method for making particles that are used everywhere. Say for example bullet hits on a wall a small particle effect. Is there anyway to reuse this effectively? Creating a whole particle effect set seems to be rather wasteful.