Single particles behaving strangely with viscous fluid

[pikok]

Hi.
I'm getting strange results in my sims with viscosity.
Trying to get a smooth creamy viscous liquid, and mostly it's working out nicely, but there are some wild single particles that behave like they're magnetic. They fly around on invisible strands or get attracted from relatively big distances to larger parts of the fluid. Jumping across letters for instance (see attached example).
Also it feels like tendrils and drops are atracted from bigger distance that they should - it feels like there's a force that brings them together before they actually are close enough to do it, if it makes any sense.
My settings:
Voxel size 0.15cm
X 100 cm
y 20 cm
z 77 cm
Timescale: 0.8
SPF 14
Viscosity 0.5

Surface tension 0.8
Droplet radius 7
Droplet formation 0.05

Drying time 0.1
sticky 0.5

Any tips regarding those crazy electrons? Thanks in advance!

[georgi.zhekov]

Hello,

Do you have any forces in the scene - it looks like something is pulling the particles? If there are not Phoenix or other external forces affecting the liquid - can you send over the scene so that we can take a look?

You can attach the scene here as a zip file or send it over through the support system at support.chaos.com (there is a submit a request top right)

Thanks!

[pikok]

Hi Georgi.
See the attached scene file. There are no additional forces.
It must be some weird scale / viscosity / surface tension combination. I can't replicate these silky drops and tendrils with more "natural" scale settings - as if the text was a cake with frosting.

[zdravko_pavlov1]

Hey,
I'm looking at your scene and trying to simulate it to check what the problem might be. The source is masked with a texture that is most likely to be some kind of an add-on or plugin. Can you please give me a hint of what might be?

[pikok]

Hi.
I believe it should be a vertex color channel map - there should be a vertex paint moidifer in the source geo. Don't know why it's not showing up for you.

[zdravko_pavlov1]

Yes, there is a vertex paint modifier. But the texture is most definitely not a standard 3DS Max Vertex Color Map. There are missing material DLLs as well.
Also some kind of modifier is missing.

What renderer are you using?

I simulated 130 frames, and there is no weird particle behavior, as far as I can tell.

[pikok]

This is a 2022 max file with a standard vertex color map. I'm using redshift for rendering (hence the 2022 version of max)- probably why the are dll's missing. I'm using also tyflow modifiers, but they are not crucial to the sim you can turn them off. As well as the missing OSM - it's "randomizer" by joker martini.
If you could swap the missing texture for your native max vertex color map and run the sim again and send me the results (preview) I would be greatful.
I'll compare it with my results. Maybe it's the max version that is the culprit here.

[zdravko_pavlov1]

Hi, Here's the simulation result calculated on two separate machines, both running max 2025.
https://drive.google.com/file/d/1cLb...ew?usp=sharing

This one is with a standard 3DS MAX Vertex Color Map.

By the way, the vertex paint doesn't look right. I wonder if it is wrong because of the many modifiers in the stack or if it is just buggy. Happened to me in the past. Painting, then saving, and it looks like this. (see attachment).
Anyway, even with the buggy vertex paint, I can't see, what is visible on your preview.

By the way, I changed the setup a bit to illustrate another approach.
https://drive.google.com/file/d/18Z3...ew?usp=sharing

Here's a link to Max 2022 scene:
https://drive.google.com/file/d/1snA...ew?usp=sharing

I used the same approach as in this tutorial.
https://youtu.be/qX2L1lQMbxQ

Maybe it will help.

Cheers.

[pikok]

Thanks a lot. That's super helpful. I'm gonna check your approach asap
Vertex paint definitely looks wrong, you're right.


Take a look at your preview - letter E in the foodiE - there's strange attraction happening, the fluid is not going down in a straight line, but skewed towards another fluid even though they are not touching. That is what I was refering to from the start - it looks like it's magically being attracted.
Is that a surface tension force or viscosity? In real life fluids have to touch first to create that sort of tension. But in Your example it feels less noticeable. I'd have to check your settings first.
What do you think?

Anyway
Thanks again - that's huge help really!

[zdravko_pavlov1]

Yes, I was wondering that myself. It is caused either by the high viscosity or the surface tension. Or a combination of both.
Let me try something else actually. I have an idea.

[zdravko_pavlov1]

I experimented a bit more, and at some point, I think I started getting something that resembles what you were describing in the original post.
I think it is a combination of factors. But the large Droplet Radius Is most likely to be the thing that contributes the most. Phoenix tries to bring the liquid together, but a distance of 8 voxels might be causing the strange behavior.

Here are some playblasts with Droplet Radius set to 0.
https://drive.google.com/file/d/1-Mr...ew?usp=sharing
https://drive.google.com/file/d/14mG...ew?usp=sharing

The difference between the two is that the one uses a noise texture applied to the entire object. That makes the letters a bit noisy. In the other one, there's a mask. The mask is just some particles scattered on the faces that point downwards. And a distance texture is pointing to it. But really you can make the mask in many other ways. Just remember that it needs to be some 3D texture. The vertex paint won't do the trick.

Here are links to the scenes saved in max 2022 format.
https://drive.google.com/file/d/1r8_...ew?usp=sharing
https://drive.google.com/file/d/1fI0...ew?usp=sharing