can you freeze a smoke simulation?

i need to do a ‘bullet time’ effect where a camera pans around a frozen explosion. i’ve got the explosion looking the way i want in blender, but i can’t seem to figure out a way to make it stay on that single simulation frame while things like the camera continue to animate.

i had hoped that when you select “blender voxels” as a texture type and tick the “use single frame” option, you could then load the .bphys file, but it doesn’t seem to work :frowning:

has anyone else come up against this problem?


I haven’t tried it, but what if you animated the properties that make the smoke move such as gravity or heat? At the start of the animation, they would be normal but at the end of the animation, they would be zero and … in principle, the smoke would now be static. If you then use the point where the smoke is static as the start of your “true” animation, that might give the desired effect?


You could bake the animation to the frame where your effect starts and copy the .bphys you want about 50 times or so. Then you should use a rename tool like “rename us” to fit the name structure. Then you hit free all bakes and simulate with the anim player (alt + a) and hit current cache to bake. This should give you the wanted effect.

thanks for the replies, definitely some interesting ideas to experiment with!

@jackoxy, i had initially experimented with your method a bit and got mixed results; sometimes it wouldn’t recognize the duplicated and renamed .bpyhs files and it would only recognize the “actual” one, which made me wonder if there is something in the internal file structure that states what frame it occurs, beyond just the file name.

but i’m happy to report the solution for my particular needs turned out to be ridiculously obvious! :stuck_out_tongue:

just run the simulation like normal, find the frame you like, and then just make that the end frame of the cache and hit “current cache to bake”. that last simulation frame will hold indefinitely, so you are free to do all your other animation after the simulation “preroll”!

hope this is helpful to anyone else who comes up against this requirement. :slight_smile:

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I also made a tut on this topic:

thanks Raub! i’d actually watched your tutorial initially and it was excellent and helpful, but for some reason i had it in my head that i had to keep the playhead on the desired frame, or else it would resume the simulation. the key realization for me is that the cache can have an independent start and end from the rest of the animation, and that the cache holds beyond its final frame and doesn’t just disappear.

although i can’t help but wonder if moving the playhead outside the bounds of a simulation cache is just a “bug” that has useful fringe benefits; i have experienced A LOT of crashing in the last few days, and i can’t tell if its just that 2.57 isn’t as stabile as i’d hoped, or if i’m doing something to provoke it!