Moving ship foam issues

[mahdidesign]

Hello, I've been trying to simulate this hull through water.
It's 58m travelling at 12 Knts (6.2 m/s)
Simulating 1000 frames to be used at 30 fps, system units in meters.

After getting a nice wakes I moved to foam and splashed with very inconsistent results.

- I have no splashes whatsoever, even by reducing the treshold and putting very high splash amounts (I tried up to 200 with no visible improvement)
- The foam on the other hand gets thrown in the air and stays floating there for many seconds.
- The size of the bubbles is very inconsistent, most of the time it's comically big.
- I tried with higher resolution of the grid (up to 100 000 000 cells) but I just end up with exponentially heavier simulated frames and the issues remain. Too many particles end up crashing vray while preparing the render.

The attached sim and render are with 1 mln cells.
Please see the attached photo for the kind of result I am looking for.

Thanks in advance for any answer

[Gosho.Genchev]

Hey there,
could you please open the Grid, Dynamics and Simulation roll-outs in addition to Foam and Splash/Mist ?
It's possible the scale of your simulation is wrong which is causing the issues we see on the screenshots.

Also, could you please show us the About dialog (it's under Simulation rollout -> About button) so we can inform you about any known issues with your particular version of Phoenix FD that may be causing this.

Cheers!

[mahdidesign]

Hi Gosho,

About and Grid settings are as follow

[Gosho.Genchev]

Awesome, looks like Scene scale is a possible reason for your problems.
When doing a simulation, you should *always* be careful with:
- the size of the objects in your scene
- the size of the Phoenix grid in your scene as displayed in the Grid roll-out

At the moment, your simulator is 139 by 24 by 3 in generic units ... There's no way for us to know if that's centimeters or kilometers. Furthermore, those units are used for other things like the Foam Size...Foam Size of 0.003 means 0.003 generic units in your case. It doesn't make sense, right ?


Please check the Units Setup section at the very top of the Ship in the Ocean tutorial. https://docs.chaosgroup.com/display/...p+in+the+Ocean
You'll notice that a couple of steps down, next to the X / Y / Z parameters is displayed the 'physical' size of the simulator as seen by Phoenix FD.

Make sure that the simulator has an appropriate size (close to the real-world size of your ship) - this should help resolve many of the problems you're facing.

Hope that helps!

[mahdidesign]

Yeah you are definitely right, the "system unit setup" that I checked was in meters, while the previous tab with "unit setup" was in generic.
I even put the reference box with the size of the yacht as reference and things were fitting until the foam detailing.

I'll run now a test and update with the result. Thanks a lot

[mahdidesign]

Hi Gosho,

Even with display unit scale on metric and system unit setup in meters I get very similar results.
Foam particles are still floating all over the trail and the few visible bubbles on the water surface are very big.

[Svetlin.Nikolov]

They are not technically floating, but rather they are being shot high in the air from under the water surface.

Your foam rising speed is 10m/s and should definitely be lower.

Cheers!

[georgi.zhekov]

Hey,

For reference you can check how our Ship scene is setup here - https://docs.chaosgroup.com/display/...Example+Scenes

The tutorial we mentioned a few posts above takes you through the most important settings you need to watch for

[mahdidesign]

Thanks Svetlin,
that parameter has removed the floating particles.
I'm doing some tests with different foam size but the parameter doesn't seem to influence my bubbles.

Georgi,
Before writing on the forum I went through the steps in the tutorial. Everything worked till the foam and splashes and I had very different results.

First of all my hull doesn't generate splashes, even with very high "splash amount" and low treshold.
No splashes meant no foam on hit which I have now to generate with the foam amount parameters.

Even by copying each parameter I am still lacking any dense foam.

Thanks for the help, Tomorrow I will try all over again starting from scratch.

[Svetlin.Nikolov]

Regarding foam size - are you sure you don't have a multiplier for the size in the particle shader that renders the bubbles? The size and 'variation large' params seem fine indeed. The difference between your setup and the tutorial is that in the tutorial the particles are rendered as points, where the size multiplier of the particle shader does not apply since there is a separate point size control.

How long did you go on the splash threshold? Do you still get no splashes with 0.001 for example? Try the extremes first. Also, maybe shift the simulator a little bit so a part of it covers a little from the right side of the ship as well - maybe the liquid gets split right on the simulation border and this is why it cannot create splashes?