Hello

What is the accepted way to smooth out a fluid simulation and mesh in Houdini?

In Softimage we have the Lagoa Fluid Shaper to iron out any unsightly blobs and lumps in the mesh. This works well with a bit of extra smooth and push when necessary. Obviosuly upping the samples of the simulation is ideal when time allows.

I have tried a similar approach in Houdini by using the Smooth and Peak operators. My results are reasonable but not great. Is this the correct route to take or is there something else I should try? A SOP I don't know about? Or should I be concentrating on getting the simulation as smooth and detailed as possible?

Hmmmm, Remesh works quite well too….

Hi Sam,

You can play with all the openVDB goodness!!!

VDB SMOOTH

Yes agreed with VDB.

VDB From Particle Fluid SOP on your points. All you need going in is points and add pscale point attribute to set your own particle scale size.

If velocity is present, you can add velocity trails as well.

Once it's a VDB surface field, you can apply any of the VDB SOPs to do whatever. Most take masks these days. You can extract any field from the flip simulation to craft interesting masks.

You can also create any volume mask in SOPs to apply to the second input to the VDB Smooth SDF SOP. One idea is to threshold the velocity with a low or high pass filter in a Volume VOP SOP and use that as a mask for the VDB Smooth SDF SOP.

Finally use the Convert VDB SOP to generate a psoup primitive and off to Alembic or to mantra for rendering. Use the Attribute transfer to transfer the velocity fields and any other attribute from the point cloud to the final surface.

Have a look at the default SOP network constructed in the particle_fluid object in any shelf created FLIP sim.

What Jeff said. The easiest way to work it out is to just create a quick default FLIP fluid (via the FLIP Fluid from Object shelf button) and then look into the some_object1_fluid node:

- vdbfromparticlefluid1: play with the Particle settings to get more detail
- convertvdb1: tweak Adaptivity setting

additionally
- add a VDB Smooth node between the two and play with its settings

I agree VDB gives a lot of flexibility. For some reason, though, I get more flickering meshes than with the Particle Fluid Surface SOP, even after using a VDB Smooth…

…or I have to force smoothing and radius so much than I lose a lot of detail.

Can you submit this case in to Support of flickering surfaced flip sims? We need to see these cases. You can ftp the files up to our server if they are too large for attachments.

oh, absolutely. I´m at work but when I get home I will look for this files. I will surely need an FTP if I am to upload a cache.

Can you submit this case in to Support of flickering surfaced flip sims?

By the way, I didn´t know you guys had a “Support of flickering surface flip sims” department. How convenient j/k

Darn spell correction… Or my fat fingers.

Sorry for the late reply, I've been away.

A huge amount of information here, thankyou all for taking the time to provide it. Very generous. :shock:

VDB here i come…