Extremely "reactive" liquids

[Underscore]

Hello!

For the past few weeks, I've been trying to create a liquid sim with Phoenix 3.10.0 for Vray using 3ds max 2018 update 4, where a character is walking/dancing with a coffee pot containing the liquid in their hands but the liquids in the coffee pot have been extremely reactive making the liquid look like its moving at super speed or almost exploding from the slightest movement.
Currently, I have the grid set to use a gravity of 15, motion inheritance of 0.0002 and a time scale of 0.2 with the coffee pot collision objects affect property set to 0.2 and it still does not seem enough along with the liquids now ending up kinda weird when they leave the pot being poured into a mug.

Any advice on how I could better calm the liquid and have it return to a more natural, water-like, way of reacting when the liquid should be poured?

Below I've included some different files, a low sample render showcasing briefly how the liquids were with mostly normal settings about a week ago, then a preview of how they are now (a little better but still far too reactive). I've also included the max file in question with the cache shown in the preview, I'll strip the scene of any un-necessary models to keep it light.


Current liquid preview:
https://www.dropbox.com/s/8m14qfsyve...ew_19.avi?dl=0

Older extremely fast and reactive liquid render:
https://www.dropbox.com/s/8m14qfsyve...ew_19.avi?dl=0

Project file with cache (cache will need a repath in the max file, also a bug with character rig might cause you to have to wiggle the green round helper at the waist to release the character from any wierd position when opening the scene):
https://www.dropbox.com/s/65q92qbgnw...t_v01.mov?dl=0


Thank you so much for your time!
Best regards!

[Svetlin.Nikolov]

Hey,

There were some changes in the nightlies to the way the FLIP liquids react to geometry - could you check how a latest Phoenix nightly behaves before we proceed?

It looks like the project file link is not the correct one though - could you check it as well?

Thanks!

[Raven]

If you have set your timescale to 0.2 only the liquid sim is in slow motion, so the object is now effectively travelling 5 times faster, this will cause the liquid to splash a lot.

[Underscore]

Hey,

There were some changes in the nightlies to the way the FLIP liquids react to geometry - could you check how a latest Phoenix nightly behaves before we proceed?

It looks like the project file link is not the correct one though - could you check it as well?

Thanks!

Thanks for the reply, Ill have a look at the nightly builds!
Also, apologies about the link slip up, heres the correct link:
https://www.dropbox.com/s/x9480eechm...blems.zip?dl=0

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If you have set your timescale to 0.2 only the liquid sim is in slow motion, so the object is now effectively travelling 5 times faster, this will cause the liquid to splash a lot.

Huh, damn, did not know I should think about it in that manner. So basically I've been making it prograssivly worse in the last few weeks. Well, I'll be sure to do a sim turning the timescale back to 1 and hoping it does not look too sped up.
Thank you very much for that info!

[Underscore]

If you have set your timescale to 0.2 only the liquid sim is in slow motion, so the object is now effectively travelling 5 times faster, this will cause the liquid to splash a lot.

Hey again, Raven ! Tried your tip on the timescale before I updated Phoenix to the nightly build Svetlin.Nikolov mentioned. It's reacting a lot more normal now, much less splashing and pouring more naturally, however, the issue I set out to fix by lowering the timescale in the first place is back, the fluid seems to be going in super fast motion, vibrating/oscillating around in the coffee pot not really seeming to settle after the liquid is first created. Any idea what I have touched to cause that? I'll be downloading the nightly build and trying again to see if this is one of the issues with FLIP reacting to geometry Svetlin mentioned.

Thanks for the help already though! Already taught me a bit more about Phoenix!

[Raven]

Try to increase your steps per frame, this will help the liquid become more stable and accurate. I tend to use 12 as a good start point.

[Underscore]

Try to increase your steps per frame, this will help the liquid become more stable and accurate. I tend to use 12 as a good start point.

Thanks for the fast reply Raven ! I'm already at 16, could try to go back to 20 where I was, I took it down to help see results a little faster.

Currently running these dynamics settings:
Motion inheritance: 0.0002
Gravity: 4
Time Steps: 16
Timescale: 0.997 (Just moved my keys in the curve editor from what they were before and did not hit 1 exactly)
default viscosity: 0.02
Droplet radius: 3

The rest are at 0

As for grid resolution I'm at somewhere around 9M cells so not the finest amount of details, again just to iterate faster.

Also see I forgot to add the video file in my last post, here's a preview of how the liquid is reacting now after getting the timescale back to 1 and lowering the gravity from 20 to 4:
https://www.dropbox.com/s/exxshbq81g...ew_21.avi?dl=0

Again thanks for the fast reply!

[Raven]

A bit difficult to tell, but it may then be as you said the rig causing the pot to move erratically. Many frames with where it all goes white, showing a there is a lot of energy through the whole liquid.
It may also be how your grid is linked to the pot, have you tried without disabling rotation linking?

[Underscore]

A bit difficult to tell, but it may then be as you said the rig causing the pot to move erratically. Many frames with where it all goes white, showing a there is a lot of energy through the whole liquid.
It may also be how your grid is linked to the pot, have you tried without disabling rotation linking?

Hmmm, the grid is currently parented to the coffeepot and rotation constrained to the floor so it's always perfectly following the pot but won't rotate with it when its lifted up and starts to pour. I have had versions where the grid was manually keyframed but I think that might have created even more splashing since the grids movements did not exactly match the pot so they kept bumping back and forth. I guess I'll run a test on a stationary grid too see if that helps any.

Thanks again!

[Svetlin.Nikolov]

Hmmm, since you don't mention the simulator scale and the Scene Scale setting under the Grid rollout, could increasing it help you get a more stable sim? If your scale it too low, the fluid will simulate in a too chaotic way, so you can stabilize this by boosting the scale Phoenix thinks the simulated world is in.

[Underscore]

Hmmm, since you don't mention the simulator scale and the Scene Scale setting under the Grid rollout, could increasing it help you get a more stable sim? If your scale it too low, the fluid will simulate in a too chaotic way, so you can stabilize this by boosting the scale Phoenix thinks the simulated world is in.

Sorry for the late reply wanted to test your suggestion before I replied. Been working at this for the last week. Had a look at your suggestion and increasing the scene scale in Phoenix did help to calm down the liquid but reintroduced weird behaviour when pouring, did not have much luck in keyframing the scale either. I'll just keep banging on the different dynamics settings and see where that gets me for now. Thanks for the reply!

[Svetlin.Nikolov]

Hmm, can you show how it looks now?

[Underscore]

Hmm, can you show how it looks now?

Certainly!
Heres the link to the latest preview made:
https://www.dropbox.com/s/k14ad2iv66...ew_30.avi?dl=0

It was a few days and iterations ago but it would be something along the lines of:
Motion inheritance: 0,0005
Gravity: 5
Scene scale: 3 or 4
Subsample:16
Timescale: 1

I guess that by increasing the scene scale I am able to calm the liquid down but as a side effect of it thinking its bigger its also a little slower to react when pouring/falling causing the slightly strange/undesired behavior there.

Anyway, thank you so much for your time and help in this matter!

[Paul Oblomov]

Now is it better? Max17, hate 18...

[Underscore]

Now is it better? Max17, hate 18...

Hi Paul!
Sorry for the slightly delayed response, saw your post right before i went away last night. Have tried your solution by using max 2017 and indeed you are correct. Copied your settings only changing the motion inheritance to 0,1 and the liquid is now behaving propperly it would seem. Only place it creates a larger splash is in the last turn but this is a VERY fast and very sharply animated turn. So thanks for the advice! Had not even considered using an older version of max as I was sure I was doing something quiet wrong.