Stopping and re-starting a particle emitter?

Is there an easy way to repeatedly stop and re-start a particle emitter during an animation? Or a clever trick to avoid needing to do so?

For example, if you have a rocket engine, and you want to start the engine, have the rocket move a bit, stop the engine, have the rocket settle back down, then start the engine again and have the rocket move again, etc. (I’m assuming this is happening under the influence of gravity, by the way, but the gravity isn’t the issue… just how to stop and re-start the engine!)

What I’d like would be, say, an IPO curve representing the particle emission rate, so that I could adjust the particles at the same time I adjust the position of the rocket.

My current “expected” solution is going to be to parent several different particle emitters to the rocket, do the rest of the animation, and then adjust the Start and End values of each emitter to correspond to a single burst from the rocket… but this kind of sounds like a pain in the neck, and I was hoping there might be a better way.

I did search the forums here (and poked around on BlenderWiki a bit, too) and didn’t quite find what I was looking for. I did find several comments that suggested that the particle system doesn’t use IPOs the way I want it to…:frowning:

I also know there is the “Texture Emission” thingy under Particle Motion that might be useful for this… and which I don’t know how to use yet… but what I don’t know is whether it will be easier for this particular application or not, particularly If I only need a small integer number of on/off engine bursts (say, three or four). I can imagine a scenario where texture emission might work, if, say, I could use an IPO to generate the animated texture, but this seems a little bit more elaborate for my current skill level with the animation system, and I don’t really know where to start.

I also thought about setting up an IPO that would adjust the alpha on the particle halos so that they would just be invisible when the engine is off; I’m not sure that would look right, though, and I don’t know how to do that either…

So… any suggestions? Pointers to documentation/tutorials/postings that I missed are just fine… :slight_smile:




Thanks Fligh… I think I can make that work!

Just to clarify my understanding: the time IPO is sort of tricking the particle emitter into thinking we’re on a different frame than we’re really on… is that how it works?


Yes, if you changed the Interpolation back to Bezier you’d see the particles go backwards. Experiment with moving the whole curve up to Y-zero and back down again.