Preseve liquid volume

[TubeSmokeGuy]

Hi!

I made a simple test.
I have a bottle which has a specific fill volume.

1. I created a geometry that fits the bottles volume.
2. I placed this geometry over the bottle.
3. I created a funnel object as a collider to catch the liquid from above and guide it into the bottle.
4. I used the fill object geometry with initial fill up and run simulation. Gravity, liquid and colliders, no other forces.
5. The initial fill up worked.
6. The amount of liquid that actually arrived in the bottle, filled the bottle only by lesser than the half.

I expected, that I get a complete fill of the bottle or at least a fill with a much much smaller loss.

So what happend and how can I ensure to preserve the volume?

I assume the liquid after the simulation is more dense than the liquid that is created by initial fillup, due to gravity pressure.
But is there any parameter to create enough liquid through initial fillup to counter correct that behaviour?

Something like a checkbox next to initial fillup like "consider gravity"?

Thanks and greetings!

[georgi.zhekov]

Hey,

There are a few things you can do.

First make sure your geometry is clean (no overapping faces, no open edges, etc) - you can check this via the STL check modifier in Max.
If the geometry is good, try increasing the steps per frame - if the simulation is of very low scale, the gravity pulls the entire liquid through the bottom of the bottle in one simulation step, so you need more steps in order to compensate for this.

Another thing you can try is to increase the scene scale - this will change the behavior of the sim, but you can get away with far less steps per frame.

[TubeSmokeGuy]

Thanks! So you say with enough SPF and clean geometry, the liquid generated by inital fillup must fit the bottle volume after the sim?

[georgi.zhekov]

In theory yes If something is not working correctly, let us know and we will take a look.

[TubeSmokeGuy]

Okay. I let it run with more SPF now.

Have you tried something similar over there? Would be cool if you could provide a simple example scene for such a case. It's very interesting and very useful for accurate filling.

[georgi.zhekov]

Ah, don't have anything ready at the moment, but this is a great idea so will try to make one soon.

Just as a pointer - this setup often requires a lot of steps sometimes 20-30 or even more. If you need more than this, try increasing the scene scale as otherwise the sim might take wayy too long.

[TubeSmokeGuy]

Thank you. First I tried with 8 SPF and then after your posting I tried with 24 SPF and it was way more liquid preserved, but still a lot loss. You can also see it at the file size of the AUR sequence. The files are getting smaller over time. Now I'm trying with 48 SPF.

Will increasing the scene scale not lead to unrealistic results?

[georgi.zhekov]

It really depends on the shot, sometimes you will never be able to tell the difference If it looks good to you then it is probably fine, a combination of increased scene scale and many steps is the best approach for these kind of shots.

[TubeSmokeGuy]

It looks good if there will be no visual volume loss anymore. Thats most important, because I simply need a full bottle at the end. I can tell you tomorrow how it worked.

Still looking forward to your example .

[TubeSmokeGuy]

Hey. Unfortunately I had no luck even with very high SPF (96 in last try). The collider geometries are all good and watertight.
So I roll back to faking the filling with mesh deformer animations now, because of a tight deadline and no time to try and run many sims. I look forward to your example when time comes.

Another topic:
At the end of the day a solution in PHX would be great, where you can define a fixed volume amount that an emitter should emit in total over a given time period and then stop emission.
Also some frame-to-frame check, that checks if the liquid looses volume, would be good. Combined with a smart way to add new liquid voxels to resample the lost ones.

[Svetlin.Nikolov]

Hmmm, could you send the scene over so we can check it? I have never seen a scene that cannot be fixed either with more SPF or changing the scene scale, so there might be something else going on.

If the scene is confidential, please shoot it to Support via this form: https://support.chaos.com/hc/en-us/requests/new

Cheers!