Foam not really locked to surface

[Truffi]

I am trying to have the foam sticking to the wavy ocean surface. In earlier simulations (with PhFD 3.x versions) this was easy to accomplish, the foam was produced by splashes and then more or less only moving with the water on the surface forming the desired cheese-hole pattern.
As can be seen on the screenshot with the current version using the shown settings, the green foam particles are flying everywhere (while the splashes look right). What values should I adjust to fix the foam behavior?

[Svetlin.Nikolov]

Hey, I think you assumed previous versions did something that they actually did not. It is the same liquid solver in phx 3 and 4 and we did a ton of bugfixes and only added new things. Existing features either did not change at all, or changed only slightly.

Instead, try to set B2B interaction to zero and reduce the falling speed - right now it is 10 meters per second - this is like an asteroid, so the roam dips down into the water and then shoots back up. The surface lock has no power to stop such huge force.

Hope this helps, cheers!

[Truffi]

Hey, thanks a lot for your help! When b2b interaction is set to zero and falling and rising speeds are very low it seems to stick better during the particles resim. Only a very few bubbles are in the air. Now I just have to tweak the pattern strength and foam amount.

The asteroid-like falling speed value was due to a desperate work-around, which failed -it was my way of trying to make sure the foam "snaps" to the ocean - I had no clue that the bubbles would bounce back up.

Is it correct saying that when resimulating foam, it is required to resimulate splashes as well? Marking the checkbox only for foam in the resim rollout did just entirely delete foam. It's working with both checkboxes activated though. I expected during resim the new foam could be obtained from the existing splashes. Thanks again for sharing these valuable infos!

[Svetlin.Nikolov]

Ahhh, now I noticed that there is no warning message that Splash's Foam on Hit option will not work during Resimulation. Could it be that your Foam is born from splashes entering the liquid volume, instead of naturally via the foam's birth multiplier and threshold? You can check that if disabling Foam on Hit during regular simulation also prevents foam from being born.

[Svetlin.Nikolov]

... if that is the case, then I'm afraid the solution would be to enable BOTH Foam and Splash resimulation.

[Truffi]

Yes, Foam was only produced by Foam On Hit under Splashes, not by Froam Birth (the first value in the screenshot is set to zero). A warning message for this case would be nice to have for sure.
The "Foam Birth" threshold is giving birth when the liquid is sufficently "breaking", correct?

[Svetlin.Nikolov]

Yess, more like when the liquid is stirred up and more turbulent: https://docs.chaosgroup.com/display/PHX4MAX/Liquid+Foam