FLIP and Foam

[Swihartc]

I am having a problem with using Flip. When I set up and enable my foam, the simulation will always crash on frame 25. If I turn foam off, it will pass frame 25. Is there an issue or a workaround? All other advection types work. I tried different builds as far back as 6/1/15 and it still crashes at frame 25 with foam on. I am using the 7/18/15 build currently. During the simulation, the foam counter = 0 particles even though the water is very agitated.

[Ivaylo Katev]

hi swihartc,
can we have the scene to investigate the problem?

[Swihartc]

Working with support to get it there.

[flipbook]

Interesting, I also get a crash after frame 25 after introducing animated collision object to the simulation. No foam etc. It is based on my wetmap scene https://vimeo.com/133978508

Downloaded the latest build to see if it was an old bug.

** Just changed FPS to 30 from 25... it now crashes at frame 31
*** I am using viscosity/surface tension and wetting option. Runs fine without animated geo in the sim. Here is a file for you to try, Max2014 vray 2.4...

https://www.dropbox.com/s/4fvro41uzp...crash.max?dl=0

[flipbook]

Ultra basic scene which reproduces the crash but it happens instantly when pressing simulate. Hide the animated box and simulates fine.

https://www.dropbox.com/s/1cukijc4k1...crash.max?dl=0

[Ivaylo Katev]

thanks for the report, a must say we have no full solution for animated geometry, i mean there will be particles penetrating the surface of the object, but at least it must not crash, we will fix it

[flipbook]

Ok great ... overall the random crashes when pressing stop appear to have gone

[ben_hamburg]

Huh, I don´t have any crashing issues with animated geo and flip solver. Simulating something right now with morphing geo. There is some penetration, but its hidden well away in my shot, so I can live with that.
Animated geo and physical sims are always an issue...I haven´t once gotten mParticles to work well with animated geo (surface animation, not just transform), there has always been some penetration/passing through etc.. MParticles uses that approximation method, that basically creates boxes for every face, which always leads to gaps, where particle get caught up or can pass through.
I always thought Phoenix had a way more solid way of dealing with animated surfaces.

[Ivaylo Katev]

Ok great ... overall the random crashes when pressing stop appear to have gone

happy to read this

[flipbook]

Installed 22/07/15 build and setup a basic scene and seems to work fine now with animated geo. Like you Ben I never really had any issues with animated geo in the past. It was since the wetting feature was introduced to the FLIP solver or sometime near this.

Anyway shall do some more simple tests

[Swihartc]

So far FLIP has passed frame 25 with foam and wetting turned on when used in the 7/22 build. The 7/18 build still crashes for me so I'm not sure what thats about. Will test higher resolution with this scene under load.

[Ivaylo Katev]

you mean the bug disappears in the build from 22th? that's weird because no changes in the flip solver were made since 7/16. it's possible that the crash was related to the scene interaction (outside the core) , this part has shows some activity in the period after 7/18. in all the cases we will test your scene today (if you have sent it)

[Ivaylo Katev]

Ultra basic scene which reproduces the crash but it happens instantly when pressing simulate. Hide the animated box and simulates fine.

https://www.dropbox.com/s/1cukijc4k1...crash.max?dl=0

fixed yesterday, must be available in the today's builds

[Swihartc]

Hmm... I don't think I'm out of danger yet. The FLIP solver will not crash, but it also does not create foam particles either. See image. I have tried with a PhXFoam helper and without. I have tried many combinations of gizmo control of PHX foam as well as rebuilding PHXLiquid and PHXSimulator just in case 1 was corrupt. If I do see particles being created, simulation crashes immediately. I have linked to file in dropbox if anyone can pin point my error of how to get foam to simulate with FLIP without crash.

https://www.dropbox.com/s/5tufhsthx1...scene.max?dl=0

[Ivaylo Katev]

the PHXFoam is the foam shader, it's not related to the foam birth, the foam panel of the simulator controls it. in your scene the birth has very low value, it's only 1, and the foam is low in count, but it exists. i suppose this is as expected, because this is water, no problem here until frame 80.

btw, your render setup is extremely slow, even with gi off the material of the glass and the liquid renders ages. i tried with materials from scratch and the acceleration was more than 10 times. hopefully you have some sophisticated feature and this is as expected.
some suggestions:
- increase the size variation of the foam, now it is 3, perhaps it can be 6 or more.
- increase the bounces of the foam shader, the bubbles are not too much and it's not a problem to set 2-3 bounces
- you can use mesh mode of rendering, the flip produces smooth surface, there are no grid artifacts to cut off