di- vs. convergence in Particles

[Follyx]

Hi,

what is a plausible way to reverse the divergence of particles? The classic example, a glass champagne. After a period of n frames the divergence have to stop cause my wife hate stains on the floor.. ;-) .

A Particlesystem is filling the glass.

I realiced the foam with
popgroup node with the expressioin

ingroup = !(@id%10) && @age > 0.35;

What is the apropriate way to reverse the expansion of the divergence in the foam group wich was defined in

@Cd = 0;
@density = 1000;
@viscosity = 1;
@divergence = 0.0;

if(@group_foam)
{
    @Cd = 1;
    @density = chi("density"); // ch = 9
    @viscosity = chi("viscosity");
    @divergence = chf("divergence"); // ch = 0.4
    
    if(@age>4)
    {
        @divergence = 0;
    }
}

After that I give the foam group age dependend a lift on top via a popforce. So I have my foam slowly but surly on top.
The problem is that the particles wich was influenced from the divergence stay in place even if the divergence becomes 0 again. I need a way wich leave the volume exypansion of the concerned particles (group_foam) behind - a convergence would be fantastic. Is there a way to do that without another elabrorated sophisticated sim? The concerned particle should behave as they never had a divergence.

should I increase the density, hmm, na... foam group wil sink on bottom...

the best way would be a mixer but after using it the champagne will taste stale, naa...   ;-).
AND: Interesting problem how houdini realize the rejection power of the divergented particles. How this perhaps work under the hood? Any ideas for this?

Thanks in advance

EDIT:

found a solution: with a balanced interaction of divergence, density and viscosity its a good solution to simulate foaming and collapsing liquids. Only reamins to solve the real bubbles, its expansion and collapsing paralel to the liquid di- and convergence. Still thea are just particles.

 

Edited December 5, 2020 by Follyx
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