Jump to content
ssh

Water inside of air field

Recommended Posts

Yeah thats why you need to delete the air, otherwise the surface will grow. It's probably the very last thing you want to do, ie after your Gravity Force and whatnot :). Also, take a look at how the Source Volume DOP sources it's particles - that's where I initially got the idea from.

 

The neat thing about gas particle to field is you can specify a point group so if you track water/air point groups you can keep the fluid from growing.

  • Like 1

Share this post


Link to post
Share on other sites

The neat thing about gas particle to field is you can specify a point group so if you track water/air point groups you can keep the fluid from growing.

Ah yes, microsolvers, great idea! I was kinda locked in using only the SOP Solver.

 

So I did some testing yesterday, and it is pretty straightforward creating a layer of air around your main FLIP. However, this has led me to some conclusions. According to my testing, this setup will only work good when you are pouring water - waterfall kind of setups. Anything else is like having a Drag Force cranked way up. This is with seeding air and deleting them after each timestep; keeping them works even worse.  I compared with filling the rest of the box up with air particles, and the result is a lot better and you get what you would expect - you get that nice mixing.

 

My trial for Sergeys asset on orbolt has run out, so I haven't tested but I would expect it to behave the same. I also believe the video of when he simply drops a bunch of particles in a box is with the rest filled up with air - and not actually using this. I also don't know if my method is similar to his, so out of respect of that I'll hold off sharing a .hip - unless someone can convince me otherwise. It isn't something too fancy though and it is pretty straightforward, a bunch of microsolvers essentially.

 

To sum up; waterfall? Sure! Anything else? Naaah..

Share this post


Link to post
Share on other sites

Hi,

 

encouraged by the helpfull comments here I wanted to give it a try.

I think the setup is working for waterfall and tank like effects.

The airparticle count ist rising due to the source like creation so I tried to delete them at a certain age. Unfrotunatly I was not able to do it properly. After the first "old" particles get deleted, the simulation gets unstable.

Does someone have a trick how to delete them correctly or fade them out?

 

Here's my hip and a short flipbook(without age delete).

 

http://vimeo.com/84809655

airtest.hip

Edited by LouisXIV

Share this post


Link to post
Share on other sites

Nice approach! Seems there is no way around filling up the rest with air to get it to work. Gj!

Share this post


Link to post
Share on other sites

This was my solution, reseeding the air layer like the water layer appeared to be the best method.

attachicon.gifairfield.hip

Clever! I tried to do it with reseeding as well, but I did it all wrong so it didn't work. It isn't all that different from just scattering points though, and it does suffer from the same issues as mine did. Drop some FLIP in an enclosed box with some initial velocity and you'll see what I mean, it dies down very quickly compared to filling the entire box up - and particles tend to get stuck when airparticles is spawned under/around them. Kinda behaving as a very high drag force. This is especially noticable when FLIP shoots up and hits the "roof" of the box.

Share this post


Link to post
Share on other sites

Hi,

 

encouraged by the helpfull comments here I wanted to give it a try.

I think the setup is working for waterfall and tank like effects.

The airparticle count ist rising due to the source like creation so I tried to delete them at a certain age. Unfrotunatly I was not able to do it properly. After the first "old" particles get deleted, the simulation gets unstable.

Does someone have a trick how to delete them correctly or fade them out?

 

Here's my hip and a short flipbook(without age delete).

 

http://vimeo.com/84809655

 

The trick was just to add a life attribute to your source and air particles, and turn on both age AND reap particles. Here's a file with the air set to an age of .5, which I quite like as it doesn't feel like someone blasted a bunch of air in it, but it is still much more lively than without the air. Thanks!

airtest_age.hip

Share this post


Link to post
Share on other sites

Hey Skybar,
 
Did you reseed your air particles every frame? Are they being advected at all or just seeded? When I just seed them it almost looks like my fluid is being poured into another fluid, as the air particle velocity is 0. It sims quite fast but the alternative, advecting the newly seeded particles, while slow, looks so much better (sorry no example of that).
 

airfield_rnd_v14.hip

Share this post


Link to post
Share on other sites

I did reseed every frame, yeah. It doesn't look as good as keeping them for a couple of frames though, in my opinion. I experimented with adding vel to them as well, how are you doing it? It shouldn't be that slow with a Gas Field To Particle DOP, and then just copy half of the vel to the air or something.

Share this post


Link to post
Share on other sites

It's not slow to copy the vel over, but to actually advect those air particles, while adding new ones, adds up pretty quick. I tried adding all kind of different vel to the air particles but nothing looked or behaved nicely. I'm now considering running a low res flip sim pullingin the vel field to run alongside, and grab the velocity for the air particles off that but, seems a bit overkill (read: i'm lazy).

Share this post


Link to post
Share on other sites

Hi -- I got really curious and ran my first very simple tests:

 

https://vimeo.com/95335273

https://vimeo.com/95336414

 

(vimeo is still processing them but hopefully they'll work :))

 

One probably couldn't get simpler than I did: every random 4th (or 2nd) emitted particle is "air" instead of water (so I'm basically emitting a water/air mixture). Even with this simpleton setup, the results look much nicer.

 

(Fliptank tests also looked promising. I'm planning to do a cgi re-creation of Prometheus' title sequence waterfall scene for some time now, and this technique seems like a must-have for that...)

Share this post


Link to post
Share on other sites

This turned out to be an Orbolt glitch.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×