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I haven't seen this question during a search.

I have a simple campfire simulation with smoke. When I play the animation through the first time, smoke and fire both appear and evolve correctly. HOWEVER, the next time I play it through, the smoke/fire retains the shape and color it had on the final frame. It's as though once the simulation is stopped, the fire is frozen in that form for all the previous frames. Is this a bug, or have I messed up somewhere?

My rig is: AMD FX-8310 8 core processor 8G RAM GeForce GTX 970 graphics card

It's being rendered in Cycles by CPU, but the problem shows up before rendering. Unfortunately, I haven't been able to try this on another computer, or on another version of Blender.

Any ideas?

[EDITED TO ADD:] Sorry, I have no idea how to attach a file to this post. HOWEVER, I have uploaded my .blend to google drive.

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  • $\begingroup$ Works fine for me.. Is it possible you could upload a .blend? $\endgroup$ – gandalf3 Sep 10 '15 at 21:40
  • $\begingroup$ Try to stop the animation, go to frame 1, and then start the animation again. $\endgroup$ – PGmath Sep 10 '15 at 23:41
  • $\begingroup$ @gandalf3: I couldn't attach anything, but I put a link to my google drive for the blend. $\endgroup$ – Michael Teasdale Sep 11 '15 at 23:24
  • $\begingroup$ @PGmath I've done as you suggested, and see the final state of the fire shown for every frame in preview. $\endgroup$ – Michael Teasdale Sep 11 '15 at 23:25
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This appears to be the result of a couple things:

  • Negative start frame.

    The simulator doesn't seem to like this, I suspect that it's a bug that negative start frames are even possible to set. (will report later)

  • The start of the scene animation is after the start of the simulation.

    Blender only simulates when the animation is played from the starting frame of the simulation (not sure why it worked at all in your case actually). Once the simulation is Baked or cached you can start at any point.

If you set the simulation start frame to 0 in Physics > Smoke Cache and then Bake, it works as expected.

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