A pattern appears in smoke renders: How to fix?

[4dartist]

We purchased fumefx as a solution to a long time hassle with creating billowing exhaust and steam clouds from rocket launches. We have spent the last couple days setting up and tweaking the smoke with mixed results. We were able to get the shape we want of the smoke, but had a lot of trouble getting small details without getting this pattern to appear. Can anyone suggest what we are doing wrong for such a pattern to appear? I'll list some settings:
Spaceing:7
Width: 980
Length:1500
Height:650
Adaptive: on
Sensitivity: .1

Quality 9
Max Iterations 100
Simulation steps 1
Advection Stride .75
Time Scale 1

Nurbulent Noise--
Scale:1.5 Detail:1
Frames:1

Dissipation Min Dens. 0
Dissipation Strength 0
Diffustion 1

Temperature--
Dissipation Min Temp: .1
Dissipation Strength 5.79
Difusion 0

Attached should be an example of the problem.
Also we are wondering if anyone can point us to a reference that explains the each of the most important settings do?
Mostly the top few in Simulation.
[complain] It's really hard to tweak settings when you barely know what they do and that is probably based off false assumtions. The tutorial videos were of little help: it was almost like listening to a coded msg and you had to pull clues out of it to help you because it didn't deliberatly give any information. "Advectioin Stride to .1, Time Scale to uh.. 4, Now animate turbulence like so.." I wish it was like "Advection Stride to .1, the range of Advection stride is 0 to 9999 and it effects your simulation like this and that." It's only by trial and error of each option to you know if the range is from 0 to 9999 or 0 to 1 and then trying to gather what each does exactly is harder. [/complain]

Thanks for your help! Really we are getting super close, just this pattern needs to be fixed. Well for stills.. Haven't checked the animation that rendered last night.

Benjamin Schweighart

[Rif]

1) Quality 9 is 2 much for a Sim for nothing ( almost).. ur Loosing Sim time.. I suggest to not pass 6 .. 5 and less for testing..you wont see much difference in the movement !

2) the lines that your seeing in the Rendering is mainly due to the Rendering and simming density you are using.. So whats really important is your Rendering Parameters..
Jitter Added will help you for cleaning out that effect a bit ..but most importantly density on rendering should help it out and\or soften Edges checked in your Obj\Src tab..

3) keep the advection strides to 0.5 , i dont think it does what you think it does..

Some good rendering tips are explained already here http://3dplanet.de/cgfluids/viewtopic.php?t=479

Doing High Density Smoke with Huge Details in Fume fx is ( Building Collapsing Pyroclastic Type ( whatever its called) ) , i think , the hardest Challenge atm ..

hope that helps ,

[sitnisati]

Hello,

- You can use lower spacing. Try with 5 for more detail

- You can set quality to 6 and leave max. iterations to 100. This might speed up simulation a bit.

- Use lower stride (0.4 for example) to get less dissipation and more
accurate advection. This will increase simulation time.

Artifacts in rendering are due to the very dense smoke.
You can get rid of it by adding some jittering to renderind and using lower step size as
well as reducing smoke opacity.

Parameters are explaned in more detail inside the FumeFX help file.

Hope this helps.

Regards,

Kresimir

[Capitanred]

I had that problem too, and I solved it by increasing the high treshhold in the smoke render settings up to the same number as the smoke density in the emitter...(didn't see that somebody mentioned it yet, perhaps that'll help)

[4dartist]

Thanks for your suggestions, I'm going to spend some time today and try to get better results.

[4dartist]

Ok this may be a dumb question... Where are the help files? I looked on the website (post login area) and only see tutorial videos and the plugin. And as for on my computer when i download the plugin and install it i look in the 3dsmax/plugins/afterworks/ and I don't see any help files there either. I know i am probably missing something, but i can't think of where they are.

Benjamin

[4dartist]

Here's a render of what we have so far, i just threw in a 'solid' from aftereffects as a background.

http://www.4dartist.com/cgtalk/smoke2.mov

Made some progress, we are pretty close, just need to get it to stick to the ground more, but still grow up. Thanks for your help.

PS still have no idea where the manuals are..

[sitnisati]

Hello,

Did you try to look in 3dsmax/help folder ?
Also, it should show up under 3ds max menu Help->Additional help.

Regards,

Kresimir

[harlequin]

Hi all.

I was wondering what did actualy solved the problem with the artifacts, 4dartist? We had many answers, but which one solved the problem?

I also got questions about the solutions:
- increasing the high treshhold in the smoke render settings up to the same number as the smoke density in the emitter
- You means to increase the high treshhold to the same value as the smoke amount in the obj/src tab, right?

- You can get rid of it by adding some jittering to renderind and using lower step size as well as reducing smoke opacity.
- When you talk about jittering, does it worked in the same way as the step size, the lower the value , the finer the effect?

Thanks in advance guys,

Simon

[sitnisati]

Hi all.

I was wondering what did actualy solved the problem with the artifacts, 4dartist? We had many answers, but which one solved the problem?

I also got questions about the solutions:
- increasing the high treshhold in the smoke render settings up to the same number as the smoke density in the emitter
- You means to increase the high treshhold to the same value as the smoke amount in the obj/src tab, right?

- You can get rid of it by adding some jittering to renderind and using lower step size as well as reducing smoke opacity.
- When you talk about jittering, does it worked in the same way as the step size, the lower the value , the finer the effect?

Thanks in advance guys,

Simon

Hello,

Smoke is very dense - almost solid, and since FumeFX is calculated on the grid, you'll always see a grid. Same thing with checker map in 2D - it's hard to get a smooth version out if it without too much blur.
To fix it, you can use smaller step size for rendering and higher jittering.

Regards,

Kresimir

[Capitanred]

for the high tresh hold...it's not important if it is same as the amount, or density...but standart setting is 30 which is mostly to low for me. I increase that value mostly over 100.