Hi there. I'm doing a fluid sim and I always see people posting their sims and saying how many particles they are using but I can't seem to find where that information is.

In my flip fluid object I see a voxel count but I'm assuming that is something different.

I'm sure this answer is super obvious but it's really bugging me!
Thanks!

Middle Click and HOLD the mouse button down on any node. This will pop up a black box with information about the geometry stream up to that point in the network.

Particle count would be the number of points.

You can also turn on the geometry info in the viewport as well but MMB on nodes to query node state and info is essential to using Houdini. I must do this at least 2-3x a minute when using Houdini.


To turn on the display of geometry info in the viewport, go to the Display Options dialog and in the Guides tab, set Geometry Information to Always On. It's my current default along with Show Time enabled.

Ah ok, I had been middle clicking and looking at the voxel count and I had also seen the number of points but i wasn't sure if that was particles or not.

Is the particle separation related somehow to the number of particles? I would think the answer is yes, a smaller particle separation means more particles but is there a way to control the number of particles in a fluid sim using the flip solver?

This is kind of another topic I suppose but I'm currently doing a fluid sim that I'm trying to smooth out the look of and I'm thinking the jagged edges on my fluid is a result of not having a high enough particle count.

Yes, the count is derived from the particle separation so you don't set a specific number of particles in a fluid sim. To increase the particle count use a smaller separation and or a smaller bounding box area.

For detailed sim work you will probably need at least 32Gb to 64Gb of ram. 16Gb is ok for beginner work, however.

Gotcha, I'm working with 32gb of ram currently and my particle separation is .01 however I'm getting a lot of jitter in the particles after they land.

I have spheres that I then turned into particles using the melt object shelf tool, they fall onto a surface and spread out which is what I want but they don't spread out smoothly and some of them jump around like they're not binding or something.

I'm not really even sure if hanging several spheres in the air and dropping them is a good way to go about doing that but it seemed like it was mostly working.

Verrrrry new to Houdini as you can tell.

Jitter in the surfaced particles or in the flip particles themselves? Colliding against the default collision plane or against your own geometry/sdf collider?

My own geometry. I made it a static object, turned off the volume based collision detection because that was giving me issues, so it hits the ground just fine, moves against the walls just fine, but I think my issue is with the particles themselves.

The jitter seems to be in the particles but I'm not sure what the difference is between surfaced particles and flip particles.

Surfaced or flip particles, they are the same particles.

Are the particles sliding on the surface jittering? Or are they stopped? Can you post a scene file with the issue?

Jason: If you have not changed the default resolution of 30 for your volume collision try upping that value. There is a check box to that you can use to turn on what that collision volume looks like. You can also turn off the original geometry so you can see the collision geometry. These are just visualization tools and do not affect the sim.