Smoke Tendrils from explosion

[stelees]

Hi there,
I am trying to build upon the version of the gasoline explosion (so fuel based) and have a pflow effect that blasts out smoke like tendrils from the explosion also.

I have a basic flow that triggers 100 particles over 1 frame, the usual divergence to make them spread out and then I spawn particles behind those particles to form tails, they emit some particles with divergence also to spread out a litte. The only have a couple of frames of life so they don't hang around forever.

I just can't seem to make the tendrils look like I am expecting, they sort of just look like blobs. The image is what I am trying to achieve and the other image is what the flow is producing which to me should give me the tendril try effect and the last pic is the blobby mess I am ending up with.

Not sure why it isn't more streamlined. Should I emit alot of speed in the fire source? I feel it is close bar a couple of obviously crucial settings that I am missing?!

[Joelaff]

What mode are you using in the Phx source? I think you might want Volume Brush, but I always forget and pop open the docs.

Edit. I think it’s brush, not Inject. See? Always need to look it up.

[stelees]

yeh I tried that but then there was no emission at all, I'll go back and look again.

[Joelaff]

Your resolution looks pretty low for emission from particles as well. It may be missing some emission due to the small grid. I'm sure the Chaos folks will have some thoughts too.

[stelees]

I did a low res test as it takes a while to test,I'll bump it up to see if that all the issue is.

[Joelaff]

Make sure you scale is close to real-world as well. Like if that is a big explosion that would be 50m wide then make sure it is actually 50m wide in Max (or Maya or whatever).

[stelees]

Yeh I checked also I had 2 scenes 1cm = 10cm and 1cm =1cm and had the same outcome.

[Ivaylo Katev]

I think there is no *simple* solution, like just to tweak some parameter. The real spikes are turbulent because the pieces leaving the trails are rotating, they are always rotating. You need a source setup that covers this behavior, and good enough resolution to handle the result.

[stelees]

also just wrapping my other issue up in this at the moment. With the gasoline preset which I based things on, the fire burns away too quickly. I have set cooling now to .05 but it still burns away, should I decrease or increase the fuel depletion amount.

I was thinking of something like .5 but then I get this massive white hot glow happening.

Which way should I head for this one for the fuel settings?

[georgi.zhekov]

For the tendrils you can try to make the emitting particles smaller over time. What you can do is to use a Scale operator with the type set to Relative Successive.
Then you set the scale factor to be something like 90 or so (if the value is below 100 it will scale down the particles).

Another thing that might help for the tendrils is to to play around with the Motion velocity multiplier in the source. Try with something like 0.5 or completely turn it off - this way the velocity from the particles won't distrub the tendrils, though this way they will just hang in the air so probably adding a bit of turbulence (using a Turblenece force) and a bit of wind using Plain force will help.

As for the fuel - if you increase the cooling the sim will cool down faster. If you lower it it will burn hotter for longer. High fuel depletion will make the fuel burn faster, while if you have low fuel depletion it will burn slower.
So if you wish your fire to burn for longer you can decrease both the cooling and the fuel depletion.

[stelees]

Thanks for the info, I will loop back to this a little later. Currently rendering out a dude on fire

[stelees]

ok, would you say this is caused by the size of the trailing particles being spawned?

[Svetlin.Nikolov]

Hmm, maybe it's the size, and I am worried about the short lifespan of these trailing particles too - sounds like they would just create puffs and disappear and this might make it look grainy?

[ttdww]

This might be moot and after your delivery, but I've done exteeeeensive testing trying to perfect explosion smoke trails and here are my tips FWIW:

--grid res has to be small enough so you don't see the spherical shape of the trail heads. unless you have physical debris that is seen, unless motion blur will soften the heads, or unless you'll have glows on the tips), you'll want them to look almost like points.
--use a phx param node set to the life of the particles age so the smoke density fades to 0 as the particle life approaches 0 so you get a natural fade as the particles slow and die off, can also set it to velocity i think
--try to use a particle emission mode (sphere..) where the positions in space are joined together. if using a mesh mode, you'll need multi-frame sim steps so connect those positions. i prefer the former.
--for an even better effect, spawn particles at the tip but keep them grouped closely together so they break up the head (the way flying dirt chunks break up as they move)
--you don't necessarily have to spawn particles trails from the main particle parents, though it can help widen the arms and create branch-off trails for a natural behavior even before the sim chaos breaks up the arms. i think that made sense.
--sim, iterate, take notes, sim again.. repeat, fall back, branch off as needed, sim again ;D repeat (all this keeps you on target and avoids getting further from the goal)