Open Container Edge Problem

[GALACTUS]

Hi All

Creating an open ocean storm with foam, spray and mist. As the area I need is quite large I have a small 80m square liquid simulator which I need for geo and a larger 600m area for which will also have the foam, spray and mist.

As you know, when you simulate the ocean with WaveForce, when the liquid moves below the initial fill level even though the container is open, it creates a wall of liquid and it is this very liquid area that appears to cause issues with simulated foam, spray and mist. I have attached a few images to illustrate the problem.

As you can see the foam, spray and so on see that area of liquid as a wall, which they then hit and go flying up. This obviously is not the desired effect as we want those particles to carry on as if on an open ocean. Does anyone know a way to mitigate this, please? Was also thinking of merging the high res with the larger area, but not sure it will work with those problems in place.

Cheers

Colin

[Svetlin.Nikolov]

Hmmm, why do these particles fly up? This is the first thing we need to figure out. Does the wave force have the in its Affects list?

[GALACTUS]

Hi Svetlin

Thanks for your response.

I have attached screen grabs from the PlainForce, WaveForce and Simulator.

[GALACTUS]

Also, a wee bit off-topic, but when I up the resolution, the results of the foam, spray and mist seem different, as sometimes I have to either increase or decrease the values to reflect what I see in the low-resolution preview versions.

I understand that a resolution increase will yield different output as it has greater detail to work with, but the difference sometimes seems quite substantial.

Do forgive me, though, as I am still new at this.

C

[Svetlin.Nikolov]

Hmm, the simulator settings look right, I see only one thing - you better make sure to set Foam's B2B interaction to zero - it has no place in large scale ocean setups, it works best for beer and coffee foam, so it could create some unexpected behavior if it's not zero in your setup.

The plain force's strength is huge though - what would happen if you temporarily remove it from the scene and simulate?

As for the difference in behavior with different resolution - this is unavoidable. One trick you could use is to simulate at the final cell size, but just with a much narrower simulator so the voxel count would still be low. Once this looks correct, you can widen the simulator back to its full size. Along which axis you decide to shrink the simulator depends on what's going on with the scene. For example, in a tunnel wave setup where the wave moves along the X axis, I would shrink the simulator along the Y axis so I get a thin section of the wave.

Cheers!

[GALACTUS]

Hiya, Thanks Svetlin, I will set the B2B to zero as you have suggested and run another test.

Unfortunately, I need the PlainForce present to affect the ocean mist the is generated by the stormy waves.

I have just run a quick draft video test of the sim as it currently stands, how can I send this to you as it illustrates visually the problem more clearly? Unfortunately, I cannot release the clip publicly.

C

[Svetlin.Nikolov]

Hey, you can send anything private to Support - you gotta go to chaos.com/help and Submit a request from the the top right corner of the screen.

Cheers!

[GALACTUS]

I have sent it

[Svetlin.Nikolov]

Yes, got it! So you can see that the wave force moves way too fast, pushes the foam up and then the foam tries to fall down but it's just falling too slow.

Try increasing the Foam Falling Speed, and I also suggest slowing down the rate of change of the ocean texture that drives the wave force. Btw, here you can find more info about the Foam Falling Speed, and there is a video example too: https://docs.chaosgroup.com/display/PHX4MAX/Liquid+Foam

Cheers!

[Svetlin.Nikolov]

Hey, btw, can you also share your Dynamics settings? If you have enabled Air Effects, this would explain the difference in behavior of particles inside and outside the simulator.

[GALACTUS]

Here you go, Svetlin, and I do have Air Effects on. I just read that when on, it stops affecting particles that exit the simulator. So I have reduced the outside age from 10 to 4. and would probably have to either increase the size of the container or add an extra one to carry on the spray and mist outside of the original sim box unless you have any thoughts or workaround for this.

The other difficulty is getting the displaced ocean mesh to match the water level of the simulated ocean. I switched off Vert. Fade and set Fade Above to 0, but the offset between the 2 liquids is quite significant.

[Svetlin.Nikolov]

Yess, lower outside age sounds good! We are thinking about a tutorial for a stormy sea setup where we might need to do some tweaks and development to the code - there is a lot to be desired when merging a simulator affected by wave force with an infinite displaced ocean. Basically you need to keep the simulated waves in the container and not apply the ocean displacement over them, and only apply the displacement outside the simulator. One way to do this is to suppress the displacement where the velocity is higher than some very small number, e.g. 0.001 - you can do this using the Fade Above Velocity option in the Rendering rollout. The waves will match well only with Massive Wave Force and 0 or very low Fluid Freedom. And still, there will be a visible seam at the borders of the simulation which should either be fixed in post, or worked around with the camera angle. Right now I don't have a suggestion on how to work around this with options - we might need to do changes in the plugin's code in order to make it better.

[GALACTUS]

I am sorry as I realised that I talked about everything other than the look I was going for.

Below is the reference to what I was aiming for in an open-ocean setting.

[GALACTUS]

Would need 1 sim for the Ship, another for the foreground to midground ocean with spray, mist and foam, and another infinite for distance ocean. I had intended to merge the 2 sims later, but would the difference in resolution between the 2 simulations affect the merge?

[Svetlin.Nikolov]

You can combine multiple simulators into one ocean mesh by just rendering in Ocean Mesh mode, buuuut you better not overlap them - this will likely not work.