Particle Advection

[alloboy]

Hi Guys,

I am new here, so excuse any "redundant" questions.

Currently I am trying to advect particles with Smoke velocity. But when I run the Simulation, the particles go zooming way to far and not actually sticking to the smoke like they are supposed to, (Please see picture below). As you can see, a lot of particles are actually behaving with teh smoke but right from the first frame, thousands go zooming out front. Not what I want, obviously.

I am still rather new at all this, so if someone could possibly give me an idea of what I am doing wrong that would be great. The file is now attached.

Look forward to your responses.

Thanks very much!

Comet_11_SmokeForAdvection.hipnc

Edited March 3, 2013 by alloboy

[Filipp Elizarov]

please attach your HIP file .You will get an answer much faster if file will be included.

[alloboy]

Hi,

I have attached the HIP File Now.

Thanks

Edited March 3, 2013 by alloboy

[Filipp Elizarov]

Can you create a very simple scene with preset like bilowy smoke and advect points by its vel.Bacause you scene give me really strange and unexpected result too.Even if I recreate all from scratch in your scene in still doesn't work right. Lets create a small test in another scene and talk us about results.

[alloboy]

Okay, I will give it a go and get back to you as soon as possible.

Thanks for your time

[Filipp Elizarov]

I think the problem in very high value for vel field in emitter.You rtying to add 100 by z axis and I think all problems from here.

[alloboy]

Yes I think you are correct there. Just created a test Billowy smoke and advected, it worked well. But I just put the velocity up for the emitter up to 100, same as the other file and hte particles behaved in teh same way.

I want my smoke to come towards the camera quite fast, so how else can I acheive this efftect, without puttuing the velocity of the smoke so high, in order to advect the particles?

[Filipp Elizarov]

maybe you can try to increase your velocity very smooth from 10 to 50.(animate it)

Edited March 3, 2013 by Filipp Elizarov

[alloboy]

Okay then, I will give this a go then. Thank you very much for your help. I will let you know how it goes.

Thanks a lot

[Solitude]

I've run into this before as well and here's an example file that will fix it: http://forums.odforc...es/#entry102768

It uses gas advect in a dop sim to move points instead. The way it traces the vel field is more accurate than the way the sampling works in sops on a vel field with those large velocities.

Edited March 4, 2013 by Solitude

[chiess]

Hi,

I have a similar problem with particles not behaving correctly.

I've attached a very simple scene. The particles get advected, but not entirely correct. I am not sure why it happens.

The particles basically move away from the fluid simulation, instead of staying "inside" and just being affected by it.

I can't figure out what I did wrong or which attribute I missed to change.

If someone can have a quick look at it (I am pretty sure its quick, the scene consists only basic stuff), that would be great!

Thank you,

Chris

advectedParticles_01.hipnc

[Annon]

Done you a quick one in DOPs in your scene.

There's lot of things you can add on top of this (like curl, dissipation etc), but this is the basic one.

Just copy velocities from your volume to the points, either in a SopSolver in DOPs, or post solve.

Loads of ways to do this, but this is the simplest.

advectedParticles_01_fixed.hipnc

[chiess]

Thanks ChristianW,

That works great! I'll look a bit more inside your dopnet node to understand what actually is going on.

I got it working as well, by using shelf-tools (which I actually don't really like) and the only difference I could find to my manual setup and the shelf tool setup is basically the Velocity Volumes input field. In my setup I just assigned the "import_smokefields" node, which apparently is wrong. I thought it would recognize the velocity by itself. While the shelf tool setup uses "/obj/AutoDopNetwork:`arg(dopobjscreatedby("/obj/AutoDopNetwork/pyro1"), 0)`/vel" as Velocity Volumes input. It looks like you have to specify exactly where to get the velocity from. I am not sure though and don't know how to get to such input via the select-options.

I guess the /vel specifies the attribute to look after (in that case, velocity)?

Thanks!