Hi,

I am new to FLIP. As far as I understand it, FLIP is both grid + particle simulation. In the DOP FLIP Object, I could not understand the meaning of “Particle Separation”. Below is its definition in the documentation:

“This parameter controls the interaction distance between particles in the created Particle Fluid Object. Decreasing this value will decrease the distance between your particles making it more impressive, but may also slow down your simulation, since it will take longer to simulate. Decreasing particle separation means more particles that weigh less, but add up to the same mass per unit area.”

1) Does Particle Separation equal to Grid Spacing? I am guessing so because the bigger I set it, the lower FLIP grids produced (i.e. pressure, surface, vel).

2) Why does decreasing particle separation mean more particles with less weight? Does Particle Separation control the number of particles? Actually, I've noticed that with bigger particle separation I get more particles, but I don't know why/how these particles are created? Isn't that particles are spawned only from SOP Fluid Source emitter? Who creates these new particles?

Thanks

Hi let me try and answer a few of your questions.

Does Particle Separation equal to Grid Spacing?

The grid spacing is based on the particle separation multiplied by the grid scale. If you want to increase the resolution of the simulation, the particle separation is the most direct way.

Does Particle Separation control the number of particles?

Indirectly but yes. If I have a 1x1x1 box and I decrease the particle separation, then I will need more particles to fill that box and still maintain the new interaction distance. You can also think about it as if you're filling the box with a grid and you want to have 8 particles in each voxel.. then if you decrease the grid spacing, you will need more particles to fill the box with 8 particles in each new, but smaller, voxel.

I hope that helps,
Ryan

Thanks Ryan, this was really helpful