Houdini 20.0 Nodes Geometry nodes

Particle Fluid Tank geometry node

Creates a set of regular points filling a tank.

Since 12.0

This operator is used to generate a regular set of points that fill a given tank. This can be useful for initializing a flip fluid.

Increasing the Particle Separation will lower the resolution, which will make your simulation faster to process. Particle Separation is measured in meters, so a particle separation value of 0.1 is 10 cm. The lowest possible value is 0.2, or 2 cm.

The Particle Radius Scale is a visual tool that will affect surfacing. The smaller this value is, the higher detail the surface will be. If this value is high, it will result in a smoother surface.


Particle Separation

The smallest distance between any two of the generated particles in the initial configuration.

Point Configuration

The configuration of the points to be generated, before any jitter is applied.


A loosely packed configuration that places the points at the vertices of a regular three-dimensional grid.


A tightly packed configuration placing points at equal distance from each of the three other closest points.

Water Level

How deep to fill the liquid. Measured as actual distance above the water level reference to the top of the water. To empty the tank, lower this past the bottom of the tank.


Size of the tank along xyz axes.


Position of center of tank.

Water Level Reference

The water level parameter fills the tank to an offset of this location. By having a separate parameter, you can either make the water level an absolute value or have it relative to the tank by using a ch("./tx") style expression.

Jitter Seed

Random seed for creating jitter.

Jitter Scale

The amount of jitter to apply to the positional values of the points. Jitter causes random changes to the positions of the points.


Set this value to 0 if no jitter whatsoever is desired.

Up Axis

The direction to fill the box in. Controls which way the water level cut off is applied.

Add Scale Attribute

Creates the pscale attribute and sets it to 2× the particle separation. This allows the Fluid Surface SOP to get the right scale for rebuilding the original surface.

Particle Radius Scale

The scale attribute is this multiple of the particle separation. Having the particles larger than the separation ensures no particles are lost in the gaps between voxels.

Padding Bandwidth

Pad the boundaries of the tank to the specified distance, which can help reduce boundary jittering in a FLIP simulation. This parameter is specified in multiples of the Particle Separation.

Scatter Density

Scatter points on the surface of the tank, which can help create flat surface for a FLIP simulation. For a value of 1 the scattered points will be approximately separated by Particle Separation. Increasing this value will oversample the surface.

Relax Iterations

When enabled, scattered points will be relaxed, pushed away from each other, to avoid clumping. This is done gradually, to avoid chaotic behavior and to allow control over how much relaxation takes place. More relaxation iterations results in points that are more separated from each other. A distribution of points in which they are well separated is often called “blue noise”.


The amount to oversample the points within a distance from the surface of the tank, as specified by the Oversampling Bandwidth.

Oversampling Bandwidth

The points will be oversampled to this distance from the surface of the tank. This parameter is specified in multiples of the Particle Separation.


Creates a viscosity attribute and sets it to the given value. If the fluid solver has both Viscosity and Use Particle Viscosity enabled, this will be multiplied with the fluid’s base viscosity.


Creates a density attribute and sets it to the given value. If the fluid solver has Density From Attribute set, this will be scaled against the fluid’s base density to determine the effective per-particle mass. This attribute is scale independent, so it shouldn’t vary with the particle separation.

Create Output Group

Create a group containing the generated points.

Output Group

The name of the generated output point group.

See also

Geometry nodes