Above/Below particles + displacement+ fluid motion possible issues

[flaviuscristea]

Hello there!

I am strugling a bit with an ocean simulation for some time now and hopefully you guys can help me out. There are a couple of things I would like to point out and ask for suggestions.

1-(possible bug). The parameter to render the particles Above/Under water doesn't seem to work properly. Please see the attached AboveRendering-Issues.jpg . That engine cooling water outlet is generating some polygons/a small mesh around so I assume the code behind this is looking at the normals of the mesh? so It 'read' the normals around the outlet as above/under? for know I thought of a workaround to tell the simulation to ignore the outlet mesh, so it will only emit fluid&particles but it won't generate aditional mesh around it. I need this because of a weird artifact that happens on a cluster of particles. Please see static-artifact.jpg + This wetrasnfer link https://we.tl/t-ZYmdyUXSrf

2- (suggestion/possible bug)- Please see Fluid-Moredisplace.jpg . I am trying to get as close as possible to real world simulations. Phoenix does a great job (Congrats to the devs!), but I want to push it further. I would like the ship to have more effect on the fluid, to actually feel it is pushing it away from it. I have tried to change the Motion Velocity Effect to different values but nothing happens. Even setting this to insane values like 100 makes no difference. Am I doing something wrong ? P.S. I have also tried using body force and set it to negative but that causes some weird things. I made a cylinder and tried to attract the fluid but that didn't work and also a plain force but I can't controll the fallof. It would be nice if the plain force would have a viewport visual representation of the area it affects, something similar to the old school omni lights inverse square fallof thing. I'll write about this in the Wishlist though.

3- (HELP!) - Please see the Phoenix-corona-disp.jpg . I have touched this subject on the https://forums.chaosgroup.com/forum/...foam-particles (my project manager posted this as he had access to the forums but I have a Phoenix subscription at home now so I can spam you guys with questions) And also on the Corona Forums (Svetlin was kind enough to create an account there and reply).

I understood that Phoenix actually displaces the mesh, similar to the standard Displace modifier from 3ds max, and that the details are controlled by the density of the mesh AND the detail value from Ocean Tex Map. On Ocean Mesh mode I assume Phoenix tessellates the extended part and then displaces it. I am using the value of 2.5 because if I go lower the quality isn't optimal. I have disabled the built in Phoenix displacement and added a Corona displacement on top. It took a lot of time to calculate. I thought it is because the density of the underlying mesh but I have collapsed the Phoenix Mesh(including the ocean extension) to a simple edit poly and applied the displacement modifier on top and the calculation time is 10 seconds . What I don't understand is why this happens... If visually the displacement can look really well and it needs 10 seconds to calculate, why does it take so long on the Phoenix Liquid simulator? I have also exported the mesh as .ABC + displacement and it is really fast, about 10 seconds of calculation. Any suggestion of how to reduce the calculation time + improving the horizon with the standard Phoenix ? Help ! P.S. Alembic is an idea but I need to see what to do wtih the particles + it takes huge amount of SSD space

To make a resume of what I am trying to explain:

Standard Phoenix displacement = Long calculation time (40-60 seconds) + even with horizon roughness to 1 it is still too little detail.
Phoenix simulator+ Edit poly modifier + displacement on top = Long calculation times (40-60 seconds) + detailed horizon
Collapsing the mesh to edit poly + displacement = Very short calculation times (10 seconds) + detailed horizon
Exporting to alembic + displacement = Very short calculation times (10 seconds) + detailed horizon

Thanking you all in advance!

Best,
Flavius

[Svetlin.Nikolov]

Hey,

(1)
Just updated the docs on the Subgroup since it was not explained clearly. The Above/Below subgroups use the surface of the attached Liquid Simulator. They check if a particle is inside the volume of that mesh or outside it, and then skip rendering it if it fails the condition. They don't check the particles only against the ocean level, but take the entire mesh, including liquid splashing above the ocean surface, or air pockets below the ocean surface. Looks like the latter is your case - there is an air pocket around this geometry, so if you choose to render only the particles in the "Above" group, any particles inside that air pocket will render as well.

If you want to remove the entire air pocket from the mesh, however, this should happen automatically if under Dynamics of the Simulator you have "Fillup for ocean" enabled during simulation - can you double check if this option was on or off? If it's On, it would fill any air pockets below the ocean surface when meshing - the particles will still be there, but the air pocket will not mesh - https://docs.chaosgroup.com/display/...ics-Parameters

(2)
Indeed sounds like a bug - the Motion Velocity Effect of the ship hull's Phoenix props should be the way to go. Maybe something is off when the Ship and Simulator are moving together - how do you link them?

You can preview the effect of forces on the sim from the Preview rollout - there is a Forces checkbox and you can pick the forces you are interested in: https://docs.chaosgroup.com/display/...w-VoxelPreview

(3)
Ahhh, there is a reduction of ocean detail by default for the viewport, this might be the key. Having not enough detail with 2.5 ocean subdivs might be connected. Can you screenshot me all your simulator settings and your ocean texture settings?

Cheers!

[flaviuscristea]

Hello there!

1. I swear I've read those documents so many times but somehow that Fillup for ocean...I missed it. It was ON in my simulation indeed.

2. I have linked the simulator to the ship by using the 3dsmax's select and link thing.

3. Aaand here I get into the displacement thing again. I am not letting it go, unless you guys kick me out of the forum ). I have stripped down the scene and organized it nicely with named layers and everything. I have a wetransfer link, please let me know how I can send it to you as I don't want to put it here in public. (do I send it to support at chaosgroup ? )

I made a test yesterday by exporting the mesh to alembic and adding the displacement on top of that and the calculations are really fast. If I put Edit poly on top of the simulator and add a displacement the calculation times incresease 4x times. I'm just curious why this happens

Thanks!

P.S. I've attached the settings

[Svetlin.Nikolov]

Ah, yes, please send it over to support at chaosgroup dot com when it's something that other should not see and the support guys will forward it to us. Thanks!

[flaviuscristea]

I have sent the scene. I am using a fairly small cell size (compared to the one used in the tutorial for example) because I need it to be as accurate as possible. For example, the water needs to hit the edge of the anchor pocket of the ship in order to create a secondary wave. I was quite happy to see the simulation really takes take into account by the way.

I have just made a new fresh scene and the Motion Velocity Effect seems not to be doing anything.... Wondering what I am doing wrong .

[Svetlin.Nikolov]

Sweet

Btw, just found it - if you convert the Simulator to an editable poly, make sure to enable this maxscript option on the Simulator: "oceanforcerenddetail". Without it, the mesh you see in the viewport and export to alembic would have less detail than the one Phoenix would render - this is by default for Ocean Sims so that your viewport does not get extremely laggy. If you set it to "true", you'll get the render-grade poly count, but your viewport may suffer (a lot).

[flaviuscristea]

Sweet

Btw, just found it - if you convert the Simulator to an editable poly, make sure to enable this maxscript option on the Simulator: "oceanforcerenddetail". Without it, the mesh you see in the viewport and export to alembic would have less detail than the one Phoenix would render - this is by default for Ocean Sims so that your viewport does not get extremely laggy. If you set it to "true", you'll get the render-grade poly count, but your viewport may suffer (a lot).

Thank you for looking into this. I will try that thing out. I assume you mean the "Use script : EDIT button" thing right?

[georgi.zhekov]

In order to enable the option Svetlin mentioned, just select the simulator and in the MaxScript editor type : $.oceanforcerenddetail = True

[flaviuscristea]

Thanks guys, will try it out soon, right now I am trying to adjust the simulation. Please don't forget to check the Motion Velocity Effect

[georgi.zhekov]

Hey,

Indeed the motion velocity multiplier won't work when the simulator is linked to an animated object. I have logged this in our system and I hope we'll have a fix soon. I will update the thread once we have something.

Thank you!