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I am trying to do a smoke/fire simulation. I can get "ignition" by setting the Start frame for the Smoke Cache bake. I want the fire to "go out" and the last generated smoke to still drift upwards. Think of a candle going out. The last of the smoke still rises for a moment. Setting the End frame for the smoke cache bake simply freezes the last simulation step. How can I get smoke/fire to cease being generated without freezing the simulation?

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  • $\begingroup$ If I understood your question, you'd like to make fire extinguish and smoke still continue flying away somewhere up from emitter. You could add Transparent shader for the smoke+fire material and keyframe the Mix shader which mixes them to make fire material slowly become opaque and smoke material to leave visible . $\endgroup$ – Mr Zak Dec 22 '15 at 16:17
  • $\begingroup$ I think you have it. However, making the smoke/fire transparent simply makes it fade in/out. It doesn't cause the simulation to start on the desired frame. There are important effects in the initial billowing of smoke. I don't want a column of smoke to fade in, I want ignition to happen and smoke start to rise. Likewise, when the fire is extinguished, smoke should stop being generated but smoke that has already been generated should continue to rise. $\endgroup$ – IRayTrace Jan 4 '16 at 13:01
  • $\begingroup$ If you're looking for something like this then I think it's enough to keyframe dissolving time, Amount of Smoke (in Smoke Flames rollout) and give smoke a texture which will control its transparency. $\endgroup$ – Mr Zak Jan 4 '16 at 16:31
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You can keyframe the Density parameter on the flow object to make it start and stop emitting smoke.

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  • $\begingroup$ This isn't bad. It does lose the curling / mushroom-head that happens when the simulation starts (initial heated air curling under cooler air). It isn't a bad way to end the simulation. If I can't find a better way I'll use this. $\endgroup$ – IRayTrace Jan 4 '16 at 13:07
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A simple way is keying the surface value (surface says the distance from mesh to emit smoke/fire). When you lower it to zero, no additional smoke will be generated.

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