Boat simulation; issues with active body

[JuhaHo]

Thanks Georgi,
I used that document, but I cannot see the effect.

[georgi.zhekov]

You can't see the effect in your render or in the docs page?

[JuhaHo]

In rendering,

Or actually I see, but no what I want to see - not at all. I'm using the latest V-Ray 3.* at the moment. I have plans to move directly to V-Ray 5, when the time is right for me.

[georgi.zhekov]

Here is the sample scene from the docs. It should work with V-Ray 3 as well.

Hope this helps.

[JuhaHo]

There's one thing in Phoenix FD (among others), I don't understand - the motion inertia. I wonder, when having a moving simulator as in "Ship in the ocean" -tutorial, most of the foam is located at the front edge of the simulator. Does it have something to do with the motion inertia. It happens if I download the project file of that tutorial and simulate it. My workaround has been to start with zero acceleration and gradually get speed. My sense says that motion inertia should be of in case of moving simulator, but it's always on on tutorials like this. Can someone explain this.

I have quite hasty project where I used the Ship in the ocean -scene. The foam was on on front edge of the simulator and nothing around my ship model except the one generated by the propulsion. However the ship wake was forming correctly, so the setup was otherwise correct in my scene.

[JuhaHo]

Then I have another question concerning the Ship in the ocean -tutorial. I wonder what is eating all that RAM. I see Max crashing on most of my rendering attempts. When looking at resource monitor, I see that 225 GB of RAM is used by the time of the crash and I only have 96 GB installed. Any Ideas om how to reduce memory usage without losing too much quality.

Regarding underwater goggles and caustics. I have watched numerous tutorials and done the scenes according those. They works as they should do,but as soon I merge my own geometry the effects are gone. What I need is a scene where I see the above and below the surface. With camera clipping the above part is easy, but I don't get the underwater look even if I do another shot without clipping and water level raised above the camera level. I have tried V-Ray environment fog too. Any ideas on that?

[georgi.zhekov]

Hey,

You can find more about the Motion inertia here - https://docs.chaosgroup.com/display/...iquid+Dynamics

As for the foam - this depends on the birth threshold for the foam. You can check how each particle type is born and dies here - https://docs.chaosgroup.com/display/...les+Life+Cycle
Generally for your case reducing the foam birth threshold should help to create foam around the ship as well. If you have unwanted foam on the simulator's edge you can kill it either with the Particle Tuner inside of Phoenix 4 or you can use the Birth volume option in the Foam settings - you can find more about them here - https://docs.chaosgroup.com/display/PHX4MAX/Liquid+Foam

Regarding the crashes - can you send us such a scene along with a problematic cache file? Can you show us your scene settings so we can give you advice on how to reduce the RAM? Generally reducing the particle count, lowering the Ocean subdivs (this will have impact on the quality of ocean rendering so be careful) and reducing the Off-screen margin (if you're using any) should help.

Can you show us references for the underwater shot and how your setup looks like? If you need to see above and under the water, probably environment fog + a gizmo geometry should help. The geometry for the gizmo should be below the water surface - this way the fog will affect only the bottom part.

Cheers!

[Joelaff]

Interesting discussion.


Some (possibly obvious) things:

Reducing the Count Multiplier parameter in the Particle Shader(s) (PHXFoam) to a fraction of one (e.g. 0.5) will reduce the number of particle rendered without re-simulating. This will reduce the memory footprint quite a bit. Also, Optimize Congestion will remove overlapping particles, which often means a LOT of particles, and can reduce memory.

Disabling the Volume Light Cache might help with memory too (though it may slow down, or speed up your render (always worth playing with)).

Try disabling Adaptive Lights. I have seen this speed up PHX scenes quite a bit, and I think it reduces memory too. (?)

[Svetlin.Nikolov]

Then I have another question concerning the Ship in the ocean -tutorial. I wonder what is eating all that RAM. I see Max crashing on most of my rendering attempts. When looking at resource monitor, I see that 225 GB of RAM is used by the time of the crash and I only have 96 GB installed. Any Ideas om how to reduce memory usage without losing too much quality.

Regarding underwater goggles and caustics. I have watched numerous tutorials and done the scenes according those. They works as they should do,but as soon I merge my own geometry the effects are gone. What I need is a scene where I see the above and below the surface. With camera clipping the above part is easy, but I don't get the underwater look even if I do another shot without clipping and water level raised above the camera level. I have tried V-Ray environment fog too. Any ideas on that?

Hey, one more thing that might answer the question immediately without having to guess and transfer scenes - right after the crash, please check the Phoenix log file (in C:\PhoenixFD). Look for tags saying [ERROR] or [WARNING]. Also, make sure you are using the latest Phoenix - we're constantly adding more and more checks for out of memory to the different algorithms.

And one more question - is it this tutorial you follow when you get the crash: https://docs.chaosgroup.com/display/...p+in+the+Ocean? At what step does it happen and are you doing anything different from the tutorial, e.g. using higher render resolution or simulation resolution?

[JuhaHo]

Thanks for the comments,

Just crashed last night during rendering. I waited a hour or so rendering to begin. Its says "Transforming vertices" and starts eating up memory as much as it can find. The log file was only a few rows. But I found the 23 MB back up. I didn't read every line, but I could not find any errors. Generally the simulation settings are very moderate. I even simulated the scene again with much more lighter settings, but it didn't change anything. I don't know what to try anymore. I checked the particle count multipliers too as suggested by Joelaff and hey both were 1.0.

[Joelaff]

I was suggesting to set the multiplier low... Below 1.0. I usually start out like 0.01 and make sure things render. This will render 1% of your particles. Then gradually increase them. A lot of the time I find I don't need a full 1.0

Good luck!

[JuhaHo]

I was suggesting to set the multiplier low... Below 1.0. I usually start out like 0.01 and make sure things render. This will render 1% of your particles. Then gradually increase them. A lot of the time I find I don't need a full 1.0

Good luck!

I normally suffer too few foam particles to get decent amount of foam I sometimes use up to value of 10.0. For me the value 1.0 has been minimum. For some reason Phoenix FD generates unnaturally low amount of foam particles. On attached screenshot can be seen, there's almost no foam on the sides. It doesn't generate any wake neither. The foam comes from propulsion. What I want to see, is wake and foam on sides. Only way I know, is to create an additional bulge to the hull, because simulator is not working with correct designs. I wonder if there will be any changes in the future to Phoenix FD which would allow customer to use real boat geometry on simulations.

[Svetlin.Nikolov]

Oh, if it did not display any of the progress windows that say that it's collecting particles, then you most probably did not run out of memory when collecting particles. Out of memory issues with ocean scenes are almost never related to particles anyway. It's usually the ocean mesh.

Instead, please reduce your ocean subdivs - probably your render resolution is too high and the ocean mesh is getting too dense.

In the attached screenshot, are you 100% sure you don't have any Detail Reduction in the Preview rollout? Phoenix will automatically reduce the shown particles in the viewport when Auto Reduction is ON, but this will not render any less particles.

The screenshot above does not look like the Ship tutorial though. Can you elaborate more on which scene you use as a base?

Cheers!

[Joelaff]

Interesting. A lower threshold should let you produce more foam (I think mentioned above). I never really like to go over 1.0 for the multiplier because the added bubbles aren't anywhere near as accurate as simulated ones. But I could see why you would go higher if you can't get enough. Also, at a distance it likely doesn't make a huge difference.

Svetlin is likely onto the real cause in your case. So I would try that first.

I have indeed had scenes (the past three shots I have done) go insane on memory from particles, but I had something in the hundreds of millions (possibly billions... it was a lot) or more in the cache.

[JuhaHo]

Oh, if it did not display any of the progress windows that say that it's collecting particles, then you most probably did not run out of memory when collecting particles. Out of memory issues with ocean scenes are almost never related to particles anyway. It's usually the ocean mesh.

Instead, please reduce your ocean subdivs - probably your render resolution is too high and the ocean mesh is getting too dense.

In the attached screenshot, are you 100% sure you don't have any Detail Reduction in the Preview rollout? Phoenix will automatically reduce the shown particles in the viewport when Auto Reduction is ON, but this will not render any less particles.

The screenshot above does not look like the Ship tutorial though. Can you elaborate more on which scene you use as a base?

Cheers!

Thanks Svetlin,

I don't understand. I really think I used it (the ship in the ocean) as a starting template.

Maybe I should start with a fresh scene - once again.