Boat simulation; issues with active body

[Svetlin.Nikolov]

I really can't say because I'm missing a lot of info - please if you've tried any of the suggestions above, please share what the results were. Or please confirm which tutorial are you using and what steps did you take before it broke. Or, if you can share the scene, please attach it here.

[JuhaHo]

I think I found reason for memory problem. For some reason the Subdivision was set to 6.0. I don't know where that comes from, but I would never have given that value manually. Maybe it came from template, I've used at some point.

Then the foam issue. I switched to another project. I didn't use any templates, but I set up the scene according to ship in the ocean tutorial. This is a displacement boat going less than 10 knots. There's no foam on bow. The only foam comes from propulsion when I enabled particle emission with value of 500. I saw somewhat similar vessel two weeks ago when I was boating nearby waters. I took a lot of reference pictures (which I don't share here), and try to get similar behavior. The biggest f´difference at the moment is the bow foam and wake. What would be the steps for getting those?

[Svetlin.Nikolov]

Awesome, so the memory issue is down.

Now about foam birth. You are putting yourself in a position to be mislead by the preview - I'd suggest you turn off Show Mesh, and also turn off showing of the Liquid particle system. This way you'd be able to lower the Detail Reduction without Auto Reduction increasing it due to an overcrowded viewport particle drawing. And this way you'd be able to get a better idea of the amount of particles born at different places in the simulation.

In the screenshot above I see you DO get some Foam on bow. So if the foam from the propulsion comes purely from a Source, then I'd suggest just lowering the Foam birth threshold - this will allow more foam to be born naturally from contact with the ship's hull.

Cheers!

[JuhaHo]

I managed to get sufficient results for my surface portion. It was achieved by reducing the birth threshold as suggested.

Now I'm struggling with the submerged part.

[JuhaHo]

Returning to this,

I started this boat active project again from scratch. It doesn't look good at all. I wonder what it is this time.

[Svetlin.Nikolov]

Well, looks like ultra low grid resolution to me I thought we mentioned the last time that you gotta have some decent resolution for active bodies to be stable, otherwise each droplet would be like a hammer

[JuhaHo]

Yes, It might be the case. I have had much better simulation results with non active body simulation. The reason is that I have heard, with activebody simulation, the simulator cannot be moved; whole simulation has to fit one gigantic pool. With non active body simulation the simulator can be moved with the boat the boat. Is this correct?

If I could move the simulator along a path, I could make it much smaller and increase the resolution.

[Svetlin.Nikolov]

Yes, still better use a static container We have an idea how to get rid of this limitation, hopefully it's just a matter of time.

[JuhaHo]

OK, I used a static container. I gave up with the previous scene and started a new. I still don't know how to get the boat wake on sides, not to mention splashes and foam. The only foam comes from propulsion liquid source.

Do You in Chaos, have any real life speed boat hull CAD-models that You can use to evaluate the simulation to see if You get similar results?

[Svetlin.Nikolov]

Hmm, so this time we're not talking about the foam birth threshold, but about the actual liquid waves that need to be generated? Can you show us the references you are after?

[JuhaHo]

Thanks,

I believe this photo is based on the same hull.

Anyway the problem seems to be the side wake. If there's a wake there's foam and splashes too.

[Svetlin.Nikolov]

Hmm, could this liquid be raised into the air when the speedboat is making a turn, or when it is bouncing back down into the water?

Maybe cheat it by increasing the Motion Velocity of the speedboat geometry if it won't raise that much liquid in the air naturally?

[JuhaHo]

Thanks,

I changed the Motion Velocity to 10. I still can't see much wake on the sides, but foam and splashes are getting a bit wild. I have used extreme foam values and try to modify those next.

[Svetlin.Nikolov]

Yes, 10 is too extreme indeed

[JuhaHo]

Value of 5 wasn't much better. I was just watching my old boat animations made with Phoenix FD 3.x. There I got proper side wake with splashes and foam too out of the box. I wonder what broke the simulator when moving to 4.x?