Pyro smoke ball help

[tomwyn]

Hi all,

I'm trying to create a 'ball' of smoke that expands outwards at a consistent rate, with the smoke being thick & rolling, as in volcano ashes seen in this great tutorial:

https://vimeo.com/44129053

My main question would be: How to I emit the smoke evenly in every direction from a sphere's surface, rather than directly upwards? I know I can change the buoyancy lift etc but I can't seem to get the effect I want.

Would I need to emit along normals? If so, does that mean it would be easier to create my own particle sim & pyro solver from scratch rather than using a shelf tool preset?

Any tips or pointers in the right direction would be much appreciated... This is my first real venture in pyro.

Thanks,

Tomwyn.

[JuriBryan]

well with out testing it, I would say that you can lay down a point sop before the node of the shelf tool.

In there go to the particle section and then click add velocity, for the values use $NX $NY $NZ.

This way the sphere, or what ever emitter geo you use, will have a velocity value with the normals as vel. That means that you can create the normals in what ever way you want on the emitter before this point node.

Then in the volume source node in DOPs there should be a vel section, make it add and there you can also scale it until you get the look you want.

I would also in this case turn of buoyancy to get the "spherical" expansion.

Hope that helps.

Cheers,

Juri

[tomwyn]

Thanks Juri,

I've pretty much implemented everything you mentioned, and it goes a long way to getting the result I want.

However it seems like I'm now just looking at the source volume, rather than what it's actually emitting...

Would it be poss for you to have a quick look at the scene file? I feel bad because it's probably a nooby kind of issue, but I've been struggling with it all day now.

Thanks in advance!

PYRO_BALL_TEST.hip

[ikarus]

if you want fluid to expand uniformly in all directions apply your source to the divergence field

[JuriBryan]

Hi, even though my method works... it is by far not as nice as ikarus's solution.

So I created a file that uses his method to expand your volume.

it is using same micro solvers, but nothing to complicated:)

PS: I don't know why the velocity was not copied to your source volume in your file. I simple deleted everything from the dop network and reapplied to billowy smoke preset and it worked perfectly.

The problem with my method is that it does not expend evenly... since every point will shoot up some smoke and will not distribute it evenly.

PYRO_BALL_TEST.hipnc

[tomwyn]

Thanks so much for your help & time guys,

I never really thought to work on the divergence field as I'm still very much a pyro beginner, really appreciate you pointing that out to me!

I certainly think this is a long way to getting what I'd like to achieve, now I just need to figure out the best way to add some detail & tweak the forces/behavior.

Thanks again!

Tomwyn.

[tomwyn]

Hi all,

In the end, I couldn't quite get what I was after from the technique I was using before, so I've switched to using a cvex inside a shopnet.

I've got exactly the look I want, but I can't seem to figure out how to animate the noise to give me a 'rolling' cloud effect.

As I'm using the cvex, I'm not using the 'do noise' control in the smoke material, as that is what emulating in the shopnet (renders much, much faster this way, with way more intuitive updates in the viewport!)

Can anyone help me with how to animate the noise? As when I try to keyframe it or use expressions in the offset fields the node errors saying I can't use any 'time dependent' values.

Once again, any tips or benefits from experience are massively appreciated!

(scene attached, you'll need to install the otl as well.)

Cheers,

c.

staticvol.zip

[Mac.0]

Hopefully I get you right...

Do you look for this kind of noise?

pyrosphere_staticvol_001.hip

[tomwyn]

Hey Mac.0

Thanks for the tip...

That's pretty close to what I'm after, except I'd like the noise to move from the center of the sphere to the outside surface, rather than across it. Essentially as if the volume is being birthed from a particle sim at the center. Any ideas?

( I suppose I could actually try the particle sim, but the volume sim time would probably suffer, even with cached particle geo.)

Thanks!

[Mac.0]

mhm... with yout setup I dont know how to do it...

The only way would be to use a Pyrosolver and kill the buoyancy.

I tried another way, which would be quite fast, but without phisical correctness (you can use anykind of geo for it). I used the cloudFX tool for it.

pyrosphere_staticvol_002.hip

[tomwyn]

For some reason I'm getting an incomplete asset definition error on the cloud node... Did you make your scene in 12.5 by any chance?

I can see your expanding geometry... but no volume. (Maybe I should update! )

[Mac.0]

yep it's created in 12.5