Ocean Foam Resimulation

[baro]

can someone please tell me what a the benefits of re-simulation vs simulation. in my few runs at this I observed no time savings (resim took almost the same time as a sim) and after outputing all particles, the frame solder turned form about 10GB to 124GB for 600 frames. was this to be expected?

[baro]

Ivo, please clarify which exactly is the multilayered you are mentioning here "splash multiplier 5 means that single liquid particle is turned into 5 splash particles". Is it the simulations settings:


or is it int the particle system settings:


One other thing - I certainly like the idea of lower in count particles which should reflect in faster simulations, but I noticed in the FLIP optimized ship tutorial you posted in another thread, the grid count I think was 91 mil, whereas in the Classic ship tutorial there were ~50 mil cells. What I am trying to figure is what would be the minimum workable sell size/particle count that will produce dissent results.

[Ivaylo Katev]

The benefit of the resimulation exists only if the resimulated particle groups have negligible simulation time compared to the liquid, this is highly dependent on the settings. For example a beer with thick foam head has no benefits to be resimulated, because 99% of the simulation time is spent for the foam. As opposite example if you have already finished simulation and decide that you need wetmap for the rendering, the resimulation is much faster than full simulation. There is no simple rule, you just have to try. If there is no advantage, then better use full simulation, because some features are not accessible in resimulation.

Ivo, please clarify which exactly is the multilayered you are mentioning here "splash multiplier 5 means that single liquid particle is turned into 5 splash particles".

It's the splash amount.

One other thing - I certainly like the idea of lower in count particles which should reflect in faster simulations, but I noticed in the FLIP optimized ship tutorial you posted in another thread, the grid count I think was 91 mil, whereas in the Classic ship tutorial there were ~50 mil cells. What I am trying to figure is what would be the minimum workable sell size/particle count that will produce dissent results.

The FLIP solver has different performance dependencies, the grid cells were increased until the simulation time reaches the old one (or rather is a bit faster).
The main factor in the flip solver is the particle count, of course the grid size is also affecting the speed, but the relation is not simple. The main difference that you will observe after some experience is that the old solver has constant performance, regardless the liquid content, but the flip solver is highly related to the liquid amount.

[baro]

have been playing with the splash amount number.
cell size .3m, grid 75 mil
splash amount =20 (stolen from the ship example)
liquid 45 mil, foam 107k, splashes 1700
both foam and splash looked grainy, but splashes looked rather large particles


then I decrease foam size from 0.05 to 0.025 and increased splash amount to 50
results: foam 225k, splash 28k
splash particles still too large:


one more try: up-ed splash amount to 100
result: foam 396k, splash 54.9k
splash particles size still noticeably large (tinted red to be distinguishable)


somehow I don't get the feeling I am on the right path to solve this issue. What would the right path be? I thought of decreasing the cell size to 0.128m (as in the ship example), but that send the grid count to half a billion, which doesn't seem a workable solution, despite the unarguably superior solution speed of the new core.
any pointers where would be the balance between sell size/count and splash amount...?

[Ivaylo Katev]

can you run the ship scene to confirm that it produces the expected result?
your settings seem good for me, we have to be sure that you are using good build first, run the ship scene and after one night we will know.

[baro]

Ivaylo, you sensed it right. There must be something not quite right with the build I am currently using (2.25.01 Nightly Build ID: 1607126855)

On May 23th I ran the ship scene you had posted in March. I don't have record of what nightly I had used, but It took 13 h for 500 frames. The rendered video looked excellent to me.
this is what I kept form that sim:



Yesterday I started simulation of that scene and in 25 hour it was only on frame 470.


and on top of that, when I tried to test render I got this:


shall I just try a fresh nightly or would logs be of any value to you?

[Ivaylo Katev]

better run an old nightly until the problem is resolved

[Svetlin.Nikolov]

Well, actually if you were running a nightly from July 12, could you please first check with a latest nightly if the issues are still there?

[baro]

Did as requested Svetlin - simulated the ship/FLIP scene with 2.25.01 Nightly Build ID: 1608036879.
took twice as long to crunch 500 frames as with the whit the nightly from May (28 h vs. 14h):


and when I tried to render fr500 got this error message:


and when I pressed OK max crashed (did the same the other day, though I forgot to mentioned it). crash reproducible every time I try.

has anybody else tested the ship scene recently? is this only happening to me? could it be a version problem (max 2015)?

[Svetlin.Nikolov]

Alright, so the change that most likely causes the different behavior is added for the first time on July 7. Before that you should have the old behavior.

Could not reproduce the crash though... Would it be possible to send the scene over to support with the cache where it crashes? Also, is the warning message you get correct? Do you really have no liquid linked to the foam shader?

[joconnell]

Just tried the July 6th build (phoenixFD_adv_22501_max2016_vray_30_x64_26849.rar ) and it's got similar issues falling over with foam simulation!

[Svetlin.Nikolov]

Hey,

Then we might not be talking about the same thing. Do you have a screenshot of how it looks?

Cheers!

[joconnell]

Georgi in another thread just pointed pout that I was being an idiot with my settings - false alarm

There'll be a bit of moaning later on about control of splash spawning near the edges of a parented intertial forces boat grid and maybe some questions on how to avoid any edges when blending into the infinite ocean mesh but I'll wait for a sim and a render to go through first

[Svetlin.Nikolov]

Oh, sure

[Fragster]

That is all you need to do. Just switch on "Enable Particle Resimulation" and press Start (You need the cache for the resimulation to be exported with Velocity channel).
It should change only the particle behavior and keep the liquid the same.

This only applies to output particles, right? Or does the velocity have to be activated also under Grid Channels?
Now I get a message, to make sure if the "sim was run with the 'velocity' channel checked under the 'output' rollout. It is unclear whether this means both velocity options.