Viscosity Difference: 2012 Vs 2013?

[Oldcode]

Hey Everybody,

I've been using 2013 since it came out but I've been having problems with viscosity and I'm beginning to suspect 2013 may be the problem.

I'm working on a project with 9 shots. Shots 1 & 2 were done in 2012 with a viscosity of 200-300 and they look just the way I want. I've been working shot 3 for the past few weeks trying to get it right, but the viscosity never seems work. I tried it at a viscosity of 350 and instead of the nice think goo that I got previously, it looks like melted ice creme; thinker than water yes, but not the nice thick slowly oozing goo that I had before. Granted, I know every shot is different, but I'm pretty confident that something else is going on.

Before I take a week to re simulate shot 3 in 2012 to find out, has anybody noticed this before? A marked difference in the way 2012 and 2013 handle viscosity?

Thanks in advanced,

[LuisMiguel]

Hi Oldcode,

I guess you are talking about SPH emitter, because the Hybrido in 2013 doesn't have viscosity yet. There is a test made by Mehmet working with viscosity fluids in RealFlow 2013 and you can take a look at by clicking on this link below.

https://vimeo.com/67482982

luisM.

[Oldcode]

Hi Luis,

Thanks for the link. Yes, I'm talking about SPH. There's a person on the other forum who told me he's noticed the same thing.

Everything in the movie looks like you'd expect it to look with the settings he says he used, but I'm not convinced. I used a "file save as..." to create my next shot for it preserves the settings I want to use. Still...

2012 V=200 Perfect
2013 V=350 Much less viscosity.

I'm re-simulating the shot in 2012 to see. One good thing about this is if true, I can use lower substeps which means it won't take as long. The bad news is if I have to use 2012, it's not as stable as 2013 and crashes more often. I just woke up after letting it simulate all night only to find the program had crashed about 1am and a lot of time was wasted.

[LuisMiguel]

Hi,

The sph has not changed at all so it should be the same that the RF2012 does. We'll take a look at this because it is weird. Do you have the same scene to send us for RF2012 and RF2013?

Thanks

luisM.

[Otuama]

I'm looking into it too. However, I've just noticed something strange.

Here is a test using the command line in 2013.



And now not using the command line

[CG_Nema]

2012 V=200 Perfect
2013 V=350 Much less viscosity.

One thing I've noticed is that viscosity effects particles differently based on their resolution (probably because of the change in mass). But if you already knew that then it's probably not the reason that your sims are different.

[Oldcode]

Hey Otuama,

That's interesting. All the while I've been using 2013, I've been using the Command Line for it works faster. Maybe it's the Command Line of 2013 that has the glitch.

[Oldcode]

Thanks for the replies everybody.

Luis,

I'll see what I can do. The SD file in this shot is huge. Do you guys have an FTP address I can send it to?

Just to let you know, I'm up to about frame 100 of 600 frames. It's hard to tell this early on, but it looks like the viscosity is behaving in 2012.

[Otuama]

Here's a script which creates the exact same setup in both versions:

https://dl.dropboxusercontent.com/u/768 ... 0Scene.rfs

After a few tests, I can find no viscosity difference between the two versions. I have also not had the explosion issue since.

------------

I had the substeps at 150/175. Everything else is set by the script (FPS etc)

VISCOSITY = 300
STICKY= 250

2013

Vertical bar (X) = 2.60575
Horizontal bar (Y) = 0.47807


2012

Vertical bar (X) = 2.59759
Horizontal bar (Y) = 0.45919


-------------------------

VISCOSITY = 600
STICKY= 500

2013

Vertical bar (X) = 2.34589
Horizontal bar (Y) = 0.730521


2012

Vertical bar (X) = 2.32348
Horizontal bar (Y) = 0.73438

[Oldcode]

Okay, after 3 months of pulling my hair out, I think I've figured out what's going on. I'm 99.999999% sure that the problem is definitely with RF 2013. The only time the problem seems to come up is when I use an Initial State in 2013. When I do, it seems to ignore any changes I make to the viscosity setting.

In 2012, a viscosity of 200 gives me the thickness I want. But in 2013, I was raising the viscosity settings to 250, 350, and even 500, and it made absolutely no difference. The fluid was way too thin and watery. See the attached movie files. One shows the shot with a viscosity set at 200 in 2012, the other at 500 in 2013.

The problem does not seem to happen in 2013 if you build the scene from scratch and not use an Initial State from the start, or with an initial state is in a scene file created in 2012 and then imported into 2013.

At this time I'm not able to use the Command Line in 2012 so I'm creating my shots there, then bringing the scene files into 2013 where I can use the Command Line and save about 3 minutes per frame.

This problem has cost me 3 months of wasted simulation time. I could have had my project much further along, maybe even done by now. Can you fix this?