Big horrible drops on fluid simulation

Hello!

I’ve been working for the last couple of weeks in an animation using fluid simulation and I have encountered some issues with the solution.

I’ve been using a 10 meters domain and the results go from excellent to horrible. Here is a Link to the animation:

https://www.youtube.com/watch?v=twYJUhWpjkY

It hasn’t been rendered in full HD and Youtube had problems dealing with the fine details, but it’s ok to show you the problems.
As you can see, some of the splashes are nice (in particular the little drops coming and hitting the boat) but towards the end of the animation you can also see the “horribles” big drops that are totally unrealistic.

This render was made using the setup that I post in the bottom of this post but I have also tried baking at 500 res, lowering the compressibility to 0.001 (the minimum), increasing the exponent in the water viscosity to 10 (maximum).
I have also tried with and without fluid particles.

No matter what I do, I always end up getting the big drops even thou the voxel unit is much smaller than the resulting drops and now I’m running out of ideas.

How do you people deal with these situations?
Any ideas?

Thanks.

DOMAIN SETUP:
Resolution: 400
Domain real world size: 10 meters
Viscosity preset: water (base:1.0 exponent:6)
Compressibility: 0.005
Subdivisions: 2
Fluid particles: 2.0
Tracer particles: 0
Frames: 300
Simulation time: 10 sec

Bake time: 10 hours
Renderer: Cycles
Render samples: 100
Resolution: 960x540
Render time: 7 hours

Just guessing here. Could they be big because they’re closer to the camera? Did you try re-doing it with a top down view?

Yeah I think you just need to increase the focal length and pull the camera back. Nice effect.

There are several things, the camera is close to the action and the focal lenght around 28mm on Full frame. The problem is the shoot itself. It needs to be close. If I take it back I will start to see the edge of the domain and I am trying to create impact with the shoot. On the other side I have also tried to put back the cam and extend the focal lenght in a zoom like effect but then the image becomes flat and the proportion of the drops are even more problematic. I just finished a new bake and I am adding some extra splashes with particle system to see if it is possibly to hide the big drops. Will post it soon but any other idea is welcome.

Thank you guys for taking the time!

By the way, every time I post something it takes a hundred years to appear, is it the same for everyone or is it just me because I am new?

Hi Lalegion

I believe that until you have a minimum of 10 posts, your posts are moderated;
so you should not have this issue soon.

The obstacle also has an “impact” parameter, perhaps lowering it a bit may help.
(but may also reduce the ‘dramatic’ effect you are going for).

Another couple of ideas (not sure how good they are, but):

  • I assume you’re animating the rise of the ship; perhaps slow the rate of ascent,
    or the angle it comes up at; ie. throw the water away from the camera, and/or

  • animate the gravity, increasing it slightly at the ideal moment .
    (May be hard to accomplish given the long bake times to make these tweaks).

If you can figure out where they are coming from, you may be able to just stop them. They look really odd entering on the right of the frame, you could model a couple of thin wall obstacles and place them just to the right of the camera, so that there is a clear field of view and any stray droplets get stopped.

Hey Gimble, I have already tried that and the result was a bit strange, on my test it worked almost as a threshold parameter, creating a space between the water and my obstacle, maybe because for the simulator the obstacle was an object more heavier so to say. I don’t know.

It is a good idea, I’ll keep it on my mind.

I didn’t think about animating the gravity, could be interesting and I will have to try to see what would be the effect on the rest of the fluid.

Thanks a lot,
Lalegion.

One thing I haven’t tried is to rebake without any modification to see if the result it is exactly the same bake. I wonder if there is some randomness on it.

Thanks.

Ok, I collected some renders and put them together next to a short description of the setup. Youtube keeps destroying the quality (which is not the best already) so I decided to upload it to wetransfer for a better viewing.

https://we.tl/XUkGYVg5Jz
But here is the Youtube version anyway:

I found interesting that in my opinion the best looking version is the one with the lowest resolution.

lalegion.

Maybe also try gfycat.com.

So, are you working on The Finest Hours part II? :wink: You should see it if you haven’t already.

Uff… Far from that!
I’m just trying to push the simulator to resolve a complex scene. I think it is a high quality simulator and I realized that to get a good looking result will require good planning and a lot of post production work. I don’t believe that I will get a production quality shot from a raw solution directly out of the sim.

Thanks for passing by…