Glass full of ocean

[Ihno]

Hi,
Im working on a simulation for a still image. It basically is an glass full of water.
I only need the surfache and a bit water beneath to be simulated. Is it possible to somehow fill the rest of the glass with the water object without simulate it?
Tryed cap mode but it automatically generates a not cutable surfache for the whole simulator, and not only for the round glass in the middle.
After some tests I gave up and filled the whole glass, I had to raise the cell size but I think it'll still be enough.
But this leads to another problem.
The scale is miles off, I want it to look like a glass full of ocean.
So I'd like to use displacement for the surface but unfortunatly it also displaces the sides of the water object and the fade object option dosn't seem to do anything.
I use the latest nightly of Phoenix.

[Ivaylo Katev]

cover with the grid only the surface and make an object representing the water beneath with the same material like the water, make it to not react with the simulator and overlap it a bit with the the simulated area.
vray does not produce visible border when the ray crosses a border between bodies having the same material

[Ihno]

Thanks! That works.

But now I ran into another problem.
I try to let 2 whales jump out of the water. They start beneath the surfache, swim up and jump out.
Unfortunatly a big bubble arises where the whales body was. Looks like the air in the mesh is keeping its position while the model moves.
Or the water can't fill the space quickley enough. Interestingly it seems to get worse if I raise the spf. Even with a spf of 30...
Clear inside dosn't help.


Since im trying to make a still image it wouldn't bother me that much, but the bubble raises and collapses at the surface right when the whale is in the air.
Which is just when I want to render my image. And it leads to a very big splash fountain which dosn't look realistic.
Thank you in advance.

[Ihno]

Also the underpressure seems to suck air through the glass model when the whale leaves the water.

This also seems to get worse with higher spf. A very Low spf causes the water running through the wall to the outside though.
Activating clear inside for the glass model chrashes max during simulation.
I think I can simply cut this away, but I would like to know how to avoid this.

[Ivaylo Katev]

huh, that bubble problem is not easy to resolve (except full volume simulation),
actually it is a real effect, called "cavitation", but in the nature it happens only in smaller scales and higher velocities, because the stronger forces.
about the second issue - it seems like a border condition problem, it may be a new one or existing from the very beginning, if is not a problem try with earlier builds to see if it happens always

[Svetlin.Nikolov]

It would be very helpful if you could send the scene over to Support so we would be able to investigate the crash. Which Build ID are you using currently?

[Ihno]

huh, that bubble problem is not easy to resolve (except full volume simulation),
actually it is a real effect, called "cavitation", but in the nature it happens only in smaller scales and higher velocities, because the stronger forces.

I assume with "exept full volume simulation" you don't mean simulating the full volume of the glass.
I think I've seen this effects in an animal documentary about the pistol shrimp. This truly is way smaller and faster since he "shoots" with supersonic speed.
And its a vacuum if I remember rightly, so the bubble immediately collapses and won't raise to the surface. It happens so fast that's only visible in slow motion.

Anyway, I think I'm getting closer now. I hided the glass and use the Initial fill option of the simulator. Insteat of a object with Initial fill enabled in the PHX settings.
Than I build a tube above the surface and animate it down till its downer border is about 1m beneath the surface. That makes me able to open all borders and give the velocity a way to escape.
And since the water can't run through walls anymore I'm able to use a low spf which reduces the bubble problem to a minimum.

I'll slow down the animation of the tube to get rid of the Splashring and add foam. I think that will do the trick.

Edit:Actually the tube dosn't need to be animated. Had weird issues with another object when it was initially in the water. But it seems to work fine with this one.

It would be very helpful if you could send the scene over to Support so we would be able to investigate the crash. Which Build ID are you using currently?

I sended it to phoenix@chaosgroup.com(#550550). By the way, this also happens if I set my freshly created tube object to be clear inside.
I use 3ds max 2017 and Phoenix v2.25.01 Nightly (rev. 1608036879)

Edit:
Is it possible to somehow set the backup frames manually? I think of something like the "Frames" option of the time output section of the Common Parameters rollout in the Render Setup window. Where you can type 5,30,80 for example. Could be very usefull for example if you want a backup frame at a prime number like frame 53.

[Svetlin.Nikolov]

Nice idea, thanks! Also, got the crash - the reason is the combination of adaptive grid and 'clear inside'. Thank you for finding this!

[Ihno]

Nice idea, thanks! Also, got the crash - the reason is the combination of adaptive grid and 'clear inside'. Thank you for finding this!

And thank you for clearing that up
Will be a huge help to be able to make that object 'clear inside'
Will post an update after the weekend.

[Ihno]

Ok, simulation worked gread thanks again svetlin . And was quite quick ~6-10min/f
I changed the animation to be more realistic, they dont jump out that high .
I let my workstation render a picture over weekend.
Rendered 50h and reached ~20 progressive samples but I did no optimization yet.
Water fog color is still rediculus.


I'D like to use a much higher displacement.
Pitty that its added after the cutting and not before.
Are you planning to change that?

If I turn off displacement and render from side. I get those cell pattern on the sides of the simulated area.
Do I need a higher number of cells(currently its about 70m)? Or is there a trick to avoid it? Smoothing seem to make it better but It dosn't kill it and well, it smoothes the details out of my liquid.
Otherwise I'll have to create a pretty complex clipper geom to make this work.
I tryed using a distance tex with multiSubTex(to keep the 'water-beneath-the-surface' object visible) to hide the sides of the simulated area. But it dosnt work some how. It makes the surface of both objects entirely invisible and only the fog remains visible.
Ivaylo's trick works well, but I'd also need to build a more complex model for the water beneath and use push on the surface model which leads to a visible gab between glass and surface. I think I could get it to work if I play with it a bit more but you may have a quicker solution.

[Svetlin.Nikolov]

Yup, that's right - the render cutter is not working quit well in mesh mode and this is why you get the cell patterns on the side, and also it does not affect the ocean surface yet. Maybe you could work around that by using a boolean or a VRayClipper?

[Ihno]

Yup, that's right - the render cutter is not working quit well in mesh mode and this is why you get the cell patterns on the side, and also it does not affect the ocean surface yet. Maybe you could work around that by using a boolean or a VRayClipper?

Yes I think I'll do it with cap mode and the clipper. I thought about that before. But didn't tryed because I'd have to mach the geomety beneath to the wavy surface. And I think this will be a bit anoying. I may coud copy the simulator, invert the volume and use this as clipper for the water beneath... have to try.
Thanks.