Secondaries...Splash, Foam....

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FlorianK
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Secondaries...Splash, Foam....

Post by FlorianK » Fri Jul 26, 2013 11:03 am

Either I am doing something completely wrong or the current implementation of Splash is lacking something. It feels close to impossible getting out something that is good for anything. Strange cloud- like distribution, the splash particles popping away heavily (not single ones, but whole clouds). Setting them up feels like setting up something that is working completely random.

I was wondering if anybody has already gotten anything useful out of those new secondaries.
Last edited by FlorianK on Tue Jul 30, 2013 5:32 pm, edited 1 time in total.

CG_Nema
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Re: Secondaroies...Splash, Foam....

Post by CG_Nema » Sun Jul 28, 2013 8:07 am

In my experience the spawning has worked like the old Hybrido.

Can you post a screenshot of so we can have a better idea of how the settings need to be tweaked for your scene?

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FlorianK
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Re: Secondaroies...Splash, Foam....

Post by FlorianK » Mon Jul 29, 2013 3:46 pm

- Dumb particles behave in a manner they are completely unusable.
- Splash works only for fast moving objects, not as a covering layer
or when you want some extra detail in certain areas, anymore.
- Instead of evenly distributing the particles, blotches are created,
behaving like particle bombs or fireworks.
- Wet is a complete horror.

No, it was a lot better in 2012....

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LuisMiguel
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Re: Secondaroies...Splash, Foam....

Post by LuisMiguel » Tue Jul 30, 2013 11:30 am

Hi Florian,

We are taking a look into the scene and it has some tips to do better.

The cell size is too big so you can't have a good resolution to generate splashes because the splash will be generated in the position of the particles of the main simulation. Also, the dumb particles are only used when you need tons of particles without control, for instance in a scene where there is a plane crashing against water. In that case, the control is almost unnecesary and you only need many particles. In the case you wanna control over them, they would need to be liquid and adjusting the parameters as curvature threshold, position and speed variation, you can control the areas where you want the splash. Also, keep in mind that the Emission rate is the number of particles per second and per cubic meter, so once you have a good behavior you can increase the value for the emission rate if you wanna more particles, but keep in mind that the number of particles will depend on the resolution and the conditions where they will be created. I mean, if you see particles on the crest, the emission particle will add more particles there, but not in another area. For that you would need to change the curvature threshold and speed or position values, or any parameter you need.

Take a look at this video showing the splashes in a typical scene of realflow.

https://vimeo.com/67510734

Best,

luisM.

michaelwbell
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Re: Secondaroies...Splash, Foam....

Post by michaelwbell » Tue Jul 30, 2013 11:33 am

I'm trying to mess around with Hybrido secondaries now. Could it be the hybrido secondary substeps are set too low? By default I saw they were 1-20...pretty low.

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FlorianK
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Re: Secondaroies...Splash, Foam....

Post by FlorianK » Tue Jul 30, 2013 4:00 pm

Ok, after a day of R&D and some input from Angel, here's my personal advice for Splashes:

- Splash operates on the underlying particles, thus only indirectly on the domain's field. In order to get out something that is half- way acceptable, one needs to have a serious amount of particles in the areas where Splashes are to be created. On can also achieve that by increasing the Surface Sampling in the emitter.

- Dumb particles are kind of dumb. The field of application for dumb particles feels narrow, the movement seldom looks nice and so one should better use Liquid particles, instead. Maybe it would have been more clever if the default setting for Splashes was Liquid and Dumb was the optional one? Just my 2ct.

- Position Variation is crucial. This value strongly influences the way particles look upon creation and should be addressed with extreme caution. Usually, it is 0.1. For me, reducing it to 0.08 to 0.05 often got me more natural looking results. This is also a place where to fight those nasty Particle Bombs.

- Be aware of the Thresholds.

- You really need A LOT of particles for half- way nice emission.

- Even though you may have enough particles, Splashes set to liquid and your substeps are ok, it still looks quite...er...pedestrian. Instead of using the HyFLIP SPH solver, one can use a Graph. Doing so, the Splash and Foam wil be calcuated by another FLIP solver. There comes a scene withe the Demo files for Graphs, hyflip_splash.

Using this technique, the HY_Splash node only controls the seeding of the particles. After seeding, the particles are (simplified) passed over to a FLIP solver that does the rest of the calculations. Now, Splashes look as supposed to and are easy to control.

It is a bit of a pity it is not like this by default. Anyway, I can live with this little hack. It is just important to find it.

izo
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Re: Secondaries...Splash, Foam....

Post by izo » Mon Aug 05, 2013 9:24 am

Thanks for sharing Florian,

I will return here the nextime I run into splash-trouble.

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