Pattern on smoke trails

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Old 07 July 2013   #1
Pattern on smoke trails

Hello all,

Why does the smoke from Fume grid fall in equal steps? Please look at the image to see what I am talking about here.


The smoke that is emitted here is from particles that is falling down at a very high speed. What I am trying to do here is to get rid of the pattern of the smoke trails.

Please help.
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Old 07 July 2013   #2
If objects are moving quickly the easiest solution is to add more Simulation Substeps. Bump it up to 3, if that isn't enough go up to 5, ect. Should solve the problem.
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Old 07 July 2013   #3
As Johnny said, it's those sub steps. It is basically the equivalent to how it works in a Rigid Body Sim. In fact, it's actually a good way to visualize how sub steps work.

The CFL Condition number is telling you how many voxels a velocity can travel through a fume grid in 1 Step. So if the velocity is larger than the specified number, it will then subdivide to the amount of substeps you wrote in.

The BAD part is that more sub steps slows down your sim. The GOOD thing about this, is that it's dynamic - so it is only "turned on" if the condition is met. It used to not be dynamic.

Happy Simming
 
Old 07 July 2013   #4
Thanks Johnny & Michael

Perfect, Have to try it tonight. Will post the comments.
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Old 07 July 2013   #5
Originally Posted by mstarktv: The CFL Condition number is telling you how many voxels a velocity ...


It is good to see that someone actually knows how that param works! 98% of Fume users don't.
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Old 07 July 2013   #6
Thanks Johnny! I feel like understanding that small parameter really opens up understanding many simulation packages. "Why are my sims looking/acting a fool?!?!?" Sub steps!
 
Old 07 July 2013   #7
Thank you Johnny & Michael,

That worked out perfectly. Such a simple setting.

I feel my smoke looks completely flat, not much definition to it.
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Old 07 July 2013   #8
Glad it worked out! If your smoke looks flat, don't underestimate good lighting.
 
Old 07 July 2013   #9
Hi Michael,

Lighting seems to be a big challenge for me in this project. I managed to get across a lot of obstacles that I had,which were some objects being invisible and some being blacked out in the render. Now I feel like I am getting the scene lit well with 3 Vray lights. But still lacking on the definitions on the smoke.

Thanks again.
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Old 07 July 2013   #10
Sumesh, Vray lights are not supported. While they may work they may not work in all circumstances.

You need to use standard lights (with vray) and use either raytraced or shadow map shadows (AB Shadows if you have Afterburn) make sure Atmospheric Shadows option is enabled in the lights params.
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Old 07 July 2013   #11
Oh really,

That's why, even by cranking up the multiple scattering settings there seemed to be no effect at all.

Now I got another challenge, getting the scene lit up perfectly with the standard lights. That going to be awesome I guess with the smoke definitions & multiple scattering.

Can't wait to see that.

Thanks Johnny again.
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Thanks all.
 
Old 07 July 2013   #12
Finally after a lot of tweaks, I am getting a glimpse of what I can achieve eventually.

Thanks to Johnny & Michael for helping me on this.

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Thanks all.
 
Old 07 July 2013   #13
Nice, you are starting to get some good definition.. Your particle trails are still a little broken but better, much better.
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Old 07 July 2013   #14
Simulation steps is set to 3, I might bump it up again as you said to 5.
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Old 07 July 2013   #15
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