"Extract" only part of a baked liquid domain

Hello all !

I’ve been trying for days to “extract” the part I want from a baked animation and delete anyhting i don’t need, but i’ve been unsuccessfull so far. Let me explain you with a picture :

It’s a pretty basic animation of something dropping in a liquid domain, creating this long shape when falling in the water. I want to extract only that part (in green) and get rid of everything else around (in red).

I can’t just Apply the liquid physic because then it freezes it and can’t move anymore, and i need the full animated process.

I tried to make “Apply as a Shape key” and then use Shape keys to make it from flat to that form, but the result is very far from what I want.

I also tried to make just a plane instead of a cube, but it does not give the same result either…

Does anyone knows how i could proceed to get only the oblong shape in green and get rid of the red part ?


Have you tried using a Boolean modifier with a custom shape the same as the green line you want?

I just tried. The problem is that the shape is very complex for a boolean so it creates a lot of issues (mostly vertices going crazy and htting the liquid domain borders), even with a shrinkwrap modifier.

What if you group the faces? Apply a transparent material to the areas you don’t want…?

The liquid domain refuses to have more than 1 material. In Edit Mode i can see that my faces have different textures, but in Object Mode it keeps the textures that takes the most space on the model

Did you try some other modifiers in the modifier stack before the Boolean modifier. I’ve had success with a remesh and smooth modifiers on a liquid domain before also adding a Boolean to the modifier stack.

What do you mean ?

Could provide an example on how you’d do with these modifiers please ?

liquid-boolean-test.blend (835.7 KB)

Still not working :confused: Maybe the fluid sim is a bit too complex for this method to work…

Or maybe i’m just bad x) If you wanna give it a try :slight_smile: :

(couldn’t send it here directly because too heavy)

The sim’ is ready, just have to click on “Bake”

Testkawoosh1.zip (2.6 MB)

It works for me with reduced liquid domain settings. Resolution divisions I set to 64. CFL number I set to 1 only because I watched a video stating that this makes the simulation not lose volume. I also put a remesh on the isosphere that you stacked displace modifiers with noise on. I’m guessing that this might make the simulation run lighter.

How did you start your liquid domain full like this?

Oooh, i see. There is a misunderstanding i believe. The part I want to keep is only the shape created by the impact inside the water, not a cylinder around.

Maybe try using a duplicate of your icosphere that has the noise displace modifiers as the object that the boolean modifier uses. Make the strength of the displace on this duplicate a bit greater that the strength on the icosphere that is colliding with the fluid.


duplicated the liquid domain and combined booleans

Edit: sorry this might not open correctly. I got it to work though. I don’t know why it didn’t open up correctly for me after I closed it. Might be because of the bake. I’ll set it up again and send an image of the setup and a new file.

step 1 - apply a slight offset to the original liquid domain with a displace mod
step 2 - duplicate de liquid domain and use booleans to carve out the shape

or you could set your camera’s clipping range to “chopp off” the front facing and back facing walls of the liquid domain…

Ooooh really interesting ! I’ll try that tomorrow :slight_smile:

I’m surprised you didn’t have to use a shrinkwrap modifier to make it fit