PyroFX smoke bug

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maxpayne: Member; 39 posts; Joined: Dec. 2010; Offline

March 19, 2014 9:32 a.m.

Hello all. I'm trying to do smoke effect. I've got some result and I noticed that the smoke has bugs. There are “lines” in the smoke. It seems that the smoke move in voxels only to horizontal direction. Does anybody know what it is ?
Thanks.

Attachments:
smoke.jpg (118.8 KB)


eetu: Member; 606 posts; Joined: May 2007; Offline

March 19, 2014 9:48 a.m.

I've seen that stuff too. I haven't had the time to methodically chase the culprit, but my gut feeling is that it's some of the shaping operators in pyro, particularly I have my eyes on sharpening.


Sadjad Rabiee: Member; 1391 posts; Joined: Dec. 2010; Offline

March 19, 2014 1:26 p.m.

I should check your project ,I should know about your parameters and setup ,Sometimes that's because Pyro parameters and sometimes that's because Render setting ,for example sometimes we have some noise and unwanted event on the Pyro that they solved with Raytracing Engine !

So upload a simple example about your project if you can :?

https://www.youtube.com/c/sadjadrabiee [www.youtube.com]
Rabiee.Sadjad@Gmail.Com


Constantine Petrov: Member; 23 posts; Joined: Aug. 2013; Offline

March 19, 2014 6:51 p.m.

To me it looks like an effect of Disturbance.


maxpayne: Member; 39 posts; Joined: Dec. 2010; Offline

March 20, 2014 9:02 a.m.

Here is a settings of the solver. I found a video with comparing parameters. https://www.youtube.com/watch?v=qwGshtSQuxY [youtube.com]. There are a lot of the same bugs when he is comparing disturnace parameters. But disturbance is off in my case.

Attachments:
hou_settings.jpg (142.8 KB)


Constantine Petrov: Member; 23 posts; Joined: Aug. 2013; Offline

March 20, 2014 9:13 a.m.

Huh, so it's neither Disturbance nor Sharpening. Maybe Confinement then?


maxpayne: Member; 39 posts; Joined: Dec. 2010; Offline

March 20, 2014 9:20 a.m.

Probably. I should check this out.


eetu: Member; 606 posts; Joined: May 2007; Offline

March 20, 2014 10:09 a.m.

Please do, we'd all appreciate it if you found out the culprit

Btw, are you solving with OpenCL active?


maxpayne: Member; 39 posts; Joined: Dec. 2010; Offline

March 20, 2014 10:59 a.m.

Open Cl is disabled. I think that the reason in the fluid engine.


maxpayne: Member; 39 posts; Joined: Dec. 2010; Offline

March 21, 2014 3:36 a.m.

I tried to disable Confinement parameter. It didn't help.


eetu: Member; 606 posts; Joined: May 2007; Offline

March 24, 2014 5:13 a.m.

Sharpening is using the Gas Reduce Local DOP, which works on a cubical subvolume, and that could introduce axis-aligned artifacts - I presume.

“ The neighbourhood regions are always cubic in shape, despite the term radius being used. ”

http://www.sidefx.com/docs/houdini13.0/nodes/dop/gasreducelocal [sidefx.com]


maxpayne: Member; 39 posts; Joined: Dec. 2010; Offline

March 24, 2014 6:35 a.m.

Yeah but sharpening is off


xukca: Member; 50 posts; Joined: July 2013; Offline

March 27, 2014 7:25 a.m.

Last summer, when I was exploring pyro2.0 I encoutered the same issue. There was a fix suggestions in THIS http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&p=133337&highlight=#133337 [sidefx.com] thread, but I still couldnt resolve the issue.

I must try again turning off the shaping tab, when I have some free time…


maxpayne: Member; 39 posts; Joined: Dec. 2010; Offline

March 27, 2014 7:52 a.m.

Hi xukca. It seem that you had problem with a banding. It's a bit another thing.


Skybar: Member; 166 posts; Joined: March 2013; Offline

March 27, 2014 8:21 a.m.

Hmm I seem to have the same problem as well. No idea what is causing it. Everything except Dissipation under the Shape tab is turned off.


Neil78: Member; 268 posts; Joined: July 2010; Offline

March 27, 2014 2:05 p.m.

Me too - never worked out the problem…. - although I found with motion blur, DoF, and a lens convolve in Nuke, most of that stuff dissapears.

Director @ Valkyrie Beowulf
www.vwulf.com
https://linktr.ee/neilrognvaldrscholes [linktr.ee]


xukca: Member; 50 posts; Joined: July 2013; Offline

March 31, 2014 5:01 a.m.

maxpayne
Hi xukca. It seem that you had problem with a banding. It's a bit another thing.

Thanks for the replay maxpayne! If this is really a banding issue, what would be a propper solution? I could try playing with the color gradients a bit, but I somehow doubt this alone will fix the problem… Is the only viable option to introduce noise/dither and blur to the image in post as Neil78 suggested?


eetu: Member; 606 posts; Joined: May 2007; Offline

March 31, 2014 7:34 a.m.

xukca
maxpayne
Hi xukca. It seem that you had problem with a banding. It's a bit another thing.

Thanks for the replay maxpayne! If this is really a banding issue, what would be a propper solution? I could try playing with the color gradients a bit, but I somehow doubt this alone will fix the problem… Is the only viable option to introduce noise/dither and blur to the image in post as Neil78 suggested?

Did you try changing your volume filter from Box to Gaussian, and maybe increasing the size a little bit from 1.0?
(OBJnode ->Render->Shading->Volume Filter)


johner: Staff; 809 posts; Joined: July 2006; Offline

March 31, 2014 9:31 a.m.

Sometimes MacCormack advection can cause minor artifacts, so it might be worth trying BFECC advection for density and velocity. It's a bit more expensive but less prone to artifacts. (Advanced | Advection tab)


maxpayne: Member; 39 posts; Joined: Dec. 2010; Offline

April 1, 2014 1:46 a.m.

I tried this. Everything the same. no differents.

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