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Is it possible to change the emission rate of particles over time?

E.g. Start off with an initial burst of particles, then emit at a steady rate.

Here is a (poor) example of what I mean by the emission rate:

enter image description here

Is this possible to do using only one particle system? (This is necessary because the particles are being used to emit smoke)


The gif above was made by manually sliding the End value, but it gives strange and unpredictable results (as can be seen in the gif) as well as not being keyframeable.

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    $\begingroup$ Have you tried setting keyframes for the Number of particles? / Nevermind that does not work $\endgroup$ – Vader Oct 29 '13 at 21:56
  • $\begingroup$ Why not use two meshes? One with the original burst of smoke and one with the constant flow? i.e. puu.sh/56vKJ.png (I'll post an answer if it's what you want) $\endgroup$ – CharlesL Nov 2 '13 at 13:24
  • $\begingroup$ @CharlesL I thought of that, it certainty would work, but it struck me as something that you should be able to do in one particle system. Post if you want, but just note that I'm looking for an answer that does this in one mesh/particle system first :) $\endgroup$ – gandalf3 Nov 2 '13 at 16:36
  • $\begingroup$ I tried using a color ramp to affect the density and animate the color of that (black being low density and white being full), but it doesn't seem to work at all :/ But the particle code is all a big mess from what I hear, so we can only hope for Lukas to finish his work. $\endgroup$ – Greg Zaal Nov 8 '13 at 11:21
  • $\begingroup$ I've definitely run into situations where I'd much rather specify the number of particles per second, rather than the total number of particles. This is relevant to my interests. $\endgroup$ – Matt Dec 2 '13 at 21:47
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In short, there's no ready solution. Lukas Tönne was responsible for a feature known as "Paged Buffers for Particles" but at some point he stopped working on it and the feature never made it to trunk. Here's a timeline of what happened:

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This technique isn't exactly what you asked for but it could simulate. In particle settings, "die on hit" is active and there is a hidden grid type object keyframed moving through the scene as a collision object. http://youtu.be/-LkoZbOchfo

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    $\begingroup$ This works. Here's another riff on "Die on hit". Easier to control. Two collision objects offset to open and allow particles through as keyframed. youtu.be/2IoroZF1iYY $\endgroup$ – jaypjohnson Nov 9 '13 at 18:50
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If it is acceptable for the "burst-particles" to disappear once you change emission rates, Keyframing the Children settings in Particles might approach what you are hoping for. For a binary on/off effect, keyframe the red-starred section in the image below; to modulate linearly, keyframe the yellow-starred section.

Particle Children Settings Particle Burst

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  • $\begingroup$ Thanks for your answer :) Interesting idea, though I would rather that particles do not die before their time.. $\endgroup$ – gandalf3 Nov 1 '13 at 18:11

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