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Mushroom Cloud Pyro sim problems


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Hi everyone, I'm working on a pyro sim of a mushroom cloud and having trouble getting the kind of control over the shape that I'm looking for. The sim works well for about a second, making a nice mushroom cloud that rises, but then it starts to stretch in strange ways. I've tried adjusting the gas released, cooling rate etc. to try and get a better result but I think I'm missing something here. Does anyone have any advice/suggestions? I'm pretty new to pyro and am not sure what I'm missing here.



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It depends pretty heavy on what your after.

When you want to create a atomic bomb with the typical mushroom cloud I would that the basic physical correct set up (what you have) gives you what you are after.

Take a look at this

and you will see that the movement is basically the same...

Just keep in mind that the real bomb do not trigger on impact but actually somewhat 5000meters over ground.

And if you want to take is further, the explosion it self is not responsible for the destruction, its the shock wave that gets triggered by it.

Add more details by using voxels smaller grid sizes....

If you are after a more stylized explosion that hold the shape better, then I would suggest a animated emitter (a torus for example) that scales and moves up at the same time.

Then use that to emit billowy smoke, set the bouncy to something very very low if not negative to get a "waterfall" effect with the smoke rolling down, also use a higher viscosity setting.

With this you should hold the shape that you want.

Then use a particle system with the same emitter as for the smoke sim, advact the particles by the first smoke simulation.

Then feed the new particle system as fuel into a fire simulation that gets triggered by a very hot static RBD.

This should give you then a very cool looking effect when you comp the smoke and the fire over each other, with smoke that slowly "sinks" giving the impression that it indeed not smoke but dirt particles.

and the fire sells the explosion.

Hope that helps you.



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Thanks for the quick reply, Juri. Yes, I am trying to make an explosion that holds its shape better. This

is the reference I was given to work with, although it doesn't have to be exactly the same.

I'm gonna be away from my good computer for a few days but I'll definitely try your suggestion of using an animated emitter as soon as I can and post again when I see how it goes.

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Hey, Juri. I finally got a chance to try following your advice but I'm not sure what you mean by "bouncy" (sorry, new to pyro) and I didn't have much luck getting a nice "waterfall" effect :/.

I was able to get more of the general shape I wanted by finessing the basic pyro sim I had before though. Only problem is, I'm not sure how to get the downward churning effect on the outer edges like the reference video has. Is there a way to do this with the shaping tools in the pyrosolver or would I be wasting my time to keep trying? What would people suggest as the best way to get that look?



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sorry, I spelled it wrong:) I mean buoyancy lift (pyro solver under the simulation tap)

The idea behind using buoyancy for this kind of effect, if you want to keep the shape, is to animate the emitter moving up and basically forming the shape you want on the lowest level of detail.

Then you set the buoyancy lift to something negative that makes the smoke "fall" and should give it a rolling motion downwards. Then you can use some vorticles to add more interior motion.

That should help you out a bit if you want to go with a more stylized look.

For something like in your scene I would just play with cooling rates and all that to try and breakup the outer edges.

What might work, I have never done it but it could work:), is to use a sop solver that scales the density down and then use that as heat for you explosion in a vopsop to effectively multiply the heat in the main sim by it to get a fast temperature diffusion on the outer edges of your sim. That might work but as I said never done it:)

Hope that helps,


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