Hi all,

I'm just now starting to dive into the pyro fluids stuff a little deeper and I'm not able to easily get the shaping that I'm after - what's the trick to generating pyroclastic, gasoline-filled, zero-G explosions? I keep getting fluffy cotton candy, despite my repeated tries at the slot machine that is the Pyro Solver DOP. The volcano preset is a little closer to what I'm looking for, but the values don't seem to translate when I move them over. The fireball preset also doesn't give me what I want - I need the explosion to operate in zero-G, and when I remove the gravity force and the buoyancy values, I get more cotton candy.

Ideas?

Source emitter volume has noise on it to create interest when doing regular explosions. This has the most effect on the initial blast.

Try turning off the noise on the source fuel first and see what happens. Then add back a bit of noise at different frequencies on that SOP. Just view the Fluid Source SOP in your source emitter object.

I bet most of your popcorn effect is coming from the noise on the emitter source fuel.

Note that the emitter has a hollow interior. If you make it solid, you add a LOT more fuel so your bang will be harder and faster, beyond the presets so you will have to tweak.


Next is to look at the Pyro Solver Shape tab. Try turning off Disturbance, Shredding, Turbulence and Confinement. Solo each back at a time to see what each one does. Make sure to turn on the velocity visualization on the Pyro object to see how the velocity is being affected. If you work with Pyro, you gotta be watching the velocity. Velocity is everything.

Shredding, Turbulence and Confinement have their own visualization velocity options.

Disturbance adds random velocity noise in empty space (density < 0.125). Used to etch away at the emerging fireball to create surface detail.

Shredding gives you flame licks.

Turbulence is applied by default using density as the look-up ramp/mask. Since density is pretty much a mask with an explosion (goes from 0-1 pretty much at the boundary of the fire ball front), the turbulence ramp is run from 0-1 right around the boundary. If you want to work that ramp, change density to temperature and now you can have more control of turbulence throughout the explosion.

Confinement as with Turbulence also uses a ramp and adds swirls based on local velocity change (shear). Same as with turbulence, uses a control field which defaults to confinement. Confinement will shred your sim to bits if left alone. Change threshold field again to temperature and put it where you need it and then turn it off as the explosion lingers.


Btw how does a zero-g explosion look like? Any reference?

Thanks Jeff, good advice. “Popcorn” is actually what I'm going for, with that signature, hard, rolling, leading edge, as seen in the example that I posted above (shamelessly stolen from the internet).

Zero-G only refers to the sourceless, gravity-less explosions, ie:

http://www.pond5.com/stock-footage/588520/zerog-explosion-zg012hd.html [pond5.com]

Nothing unique. In the old days you'd put the explosive charge against a black background close to the ceiling of a big warehouse and film it from directly underneath so that the resulting gas cloud and debris falls towards the camera.

The other issue that I'm having is over the first few frames - I key the “gas released” value in the pyro solver up at the beginning in order to get strong initial combustion but that gives me a big glowing, featureless ball that eventually morphs into something resembling an explosion. Is there a better way to initiate the initial violent energy release while maintaining some sort of shape at detonation?

See stock footage example below. My goal is to create a result that I'm happy with and then publish an HDA that has a few parameters boiled up to reshape the result while keeping the spirit of the detonation intact.