Amount of fluid keeps increasing without discharge

[bobweb]

Hello!

I want to pour a viscous liquid from a glass into a bowl. To fill the glass I followed the Tips&Tricks page and discharged from a volume over two frames, then animated to zero. In this case the glass should be half full then, but the fluid keeps increasing, coming out of the glass, filling the bowl already. Inside the bowl it keeps growing as well. This could be a result of the cascading setup I needed to have an animated glass with attached Phoenix and inertial forces and the fixed bowl, which needs, as I have read, a discharge higher than 0, so I put that to 0,001. But it seems it is growing way too much for this small amount. And the remainings in the glass after pouring also grow again. According to the volume calculations of 3ds Max the bowl would need about 8 glasses to get filled. So, how do I stop the blob from growing before it eats us all?
Please have a look at the attached preview to see what happens. Here are the specs of my scene:
System unit 1 cm
Inscribed
Smooth
Quality 200
Method Classic
SPF 8
Cell size 0,04
Gravity 0,9
Sharpness 0
Viscosity 0,8
Wetting on
Strong surface mode on

Thanks,
Bob

[Ivaylo Katev]

no idea why this happens, can you share the scene?

[bobweb]

Thank you for the fast response, I do not have access to the file at the moment, but I will post a stripped down version of it later.

[bobweb]

Here is the scene file. Thanks for having a look!

[Ivaylo Katev]

the reason is the default interaction of phoenix with every object in the scene . this includes the second source, that is intended to be used in the second simulator, not in the first one.
now i'm waiting to see the simulation result with the fixed setup, but i'm almost sure that this is the reason.
i strongly recommend include interaction list to be used instead the default exclude list when a complex simulation like this is prepared.

[bobweb]

Ah, ok, I see. Please let me know, how your test comes out. Is this setup the right way to do this anyway? Or do you have a better way to approach this? Also I would like to ask additionally for further scene development, if there is a possibility to get higher viscosity than 1. Is this only a matter of time-scale then? Or gravity? So the fluid in the glass comes out more slowly, more like glue.
Thanks,
Bob

[Ivaylo Katev]

the test showed that the reason is not in the self interaction as i suggested, nevertheless i still recommend to use include list in such simulations.
my second suggestion is that the grid anisotropy is to blame, your grid is rotated and the gravity is directed diagonally. I have never tried this, it's very probably that the gravity pressure is overcompensated and there is residual upward velocity. i.m testing this now, and at frame 350 it seems stable.
btw, why the grid is rotated? this produces big empty areas, your grid was 1.6M cells, after the reorientation it is only 600k and simulates 3 times faster! I also decreased the conservation down to 30, because i suspect you have tried to solve the problem with high conservation.
there is something in your scene that slows down the entire interactiveness of max, and of course this makes the simulation slower, because every step the viewport is redrawn and needs about 5 sec to update. perhaps this is the container that collects the liquid in the second simulator, because it has two modifiers. it's hidden now, and with all the other optimizations the simulation runs with 5 sec/frame, the initial speed was 30 sec frame, 6 times slower.
well, it's frame 450 now and the the container is already rotated, my second suggestion was correct and the vertical gravity makes the simulation stable. perhaps the container have to be adjusted to cover the areas where the liquid have to enter into the second container.
i also changed the brush animation, it's always better to have one frame with stable 100% brush strength, so i shifted the keys one frame forward

[bobweb]

Thanks a lot for your insightful response and your support. I will try that again in a whole simulation. I have to admit, the initial rotation has only evolutionary reasons. At first I tried it all with only one container, but then the fluid did not stay in the glass during its rotation, then I linked it and tried to reach the bowl with the smallest possible grid etc.

Could you please say something to my viscosity question as well?

Thanks,
Bob

[Ivaylo Katev]

about the viscosity - phoenix is grid based and this leads to some limitations of the viscous simulations. btw there is one more factor that can increase the viscosity, but it is switched off, because makes some simulations worse. i'm considering to allow the users to use it. if you want, i can prepare a build that uses this option for you, and if you like the result, we can include it in the official builds

[bobweb]

I have built your advices in my scene and simulated again, it is better and faster now. But as it reaches the second container it still goes wild with the volume. Have I missed something? Please see the attached preview video and max scene.
About the additional viscosity function: Sure, sounds like fun, I would like to test it.

Thanks,
Bob

[Ivaylo Katev]

i suppose the reason is the small scale. in this scene we used bigger scale exactly to avoid the uprising liquid.
why the small scale produces uprising liquid? because the gravity is huge measured in the scene units. for one second a free falling object travels a distance about 100 times bigger than the size of your grid!
to have stable simulation you need very big spf, but this is slow. so, the easiest solution is just to increase the scene scale. now it is 1 cm, make it 5 cm.
and one more thing - start the simulation few frames before the rotation of the cup. there is no activity 300 frames, and you simulate all this sequence!

[wxyz]

Is a cascade mode planned for the version of Phoenix compatible with VRay 3.0?

[Ivaylo Katev]

the "cascade mode" is not a special feature, it's just a user technique that combines certain phoenix features.

[bobweb]

Thanks, changing the units makes it definitely much better - although I would prefer not to mess with the system units since this can have an impact on the rest of the scene. How about a system unit multiplier setting within Phoenix? Or is there one I did not see?

The extra simulation time was for the first tries to letting the liquid settle in the glass, but you are right, this not needed anymore now.

I still have problems keeping the overall volume of the fluid. It is not visibly growing anymore like it used to have, but as soon as the second container is reached, it just becomes more mass. I would not mind a little change, but it is about 4 to 5 times more volume in the second container. I have attached some previews with different settings.
Creating these I would really like to have something like the Max Batch Renderer for simulations, to create several simulations with different settings overnight.

Do I need really high settings for everything with several days of simulation or is there anything else I could do?

Thanks,
Bob

[Ivaylo Katev]

as i said the reason for the liquid grow is the high gravity/spf rate, if you can't change the scale, you may decrease the gravity or increase the spf. actually there is a more important reason that i found today. i did two experiments, one with liquid created using the initial fill up and one with pouring. the first one remain stable even with spf=2, the second requires very high spf to keep the liquid quantity. what is the reason? it's the hit of the liquid in the geometry! so i modified the experiment, to be similar ot your simulation, i made a brush cylinder that fills the liquid. i ran two sims, the first one was with radius a bit smaller than the container size, the second one was a bit bigger than the container size. what is the idea? the first setup creates a small crevice between the initial liquid and the wall, the liquid fits in the container that produces hit in the walls, the second one does not produce crevice and the liquid does not hit the walls. the result was very different! the first simulation behaves exactly like you sim, it grows, the second one does not grow. let say it again - if you simulate vith very high spf, both the sims will keep the quantity, but the low spf is compatible only with the second simulation. so, just make your source to penetrate the walls, including the botom, and you can keep the 1cm scale
and one more thing: it seems like your cascade connection is not set properly, the source in the second simulator does not transfer the liquid velocity. this is because in the PHXSource_Auffang source you have not enabled the velocity chackbox, that means the source does not affect the velocity and the created liquid has zero velocity. i think this is because in our old versions the checkbox was enabled by default. we changed this in order to make the brush setup easier (it's a very used setup)