This parameter controls the interaction distance between the fluid’s particles. Smaller values decrease the distance between your particles making the fluid 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.

For correct simulation results, also use this value in the FLIP Solver’s Particle Separation in the Setup sub-pane.

A scaling factor used to calculate the division size of the advection grid from the particle separation. Note that smaller values increase the number of voxels and RAM usage. The default should be good for most applications, but you can get more details with smaller values. For more detailed fluids you can try values between 1.5 and 1.7.

In most cases, domains are convex containers with more or less box-like shapes. Instead of an expensive VDB surface, Implicit Bounds creates a fast convex hull to represent the container’s geometry. Open Node Info and choose View Output ▸ Container. The HULL point group contains the container object’s vertices, while surface is 0,0,0.

Set the domain’s dimensions.

Set the domain’s position.

The amount of force to apply to a unit-massed object. Because the force is scaled by the mass, objects will undergo this acceleration. The force’s direction is controlled through the Gravity Direction parameter.

If your units are meters, seconds, and kilograms, 9.81 is a good value for Earth’s gravity. With feet, seconds, and pounds, 32 is a good value for Earth’s gravity.

You can control the direction of the Gravity force by defining a vector. The default of 0,-1,0 simulates the natural direction along the Y axis.

Here you set a uniform mass density value for the entire fluid. The default value of 1000 represents the density of water in kg/m^3.

Turn on this parameter for a per-particle density. The density values have to be defined separately, e.g. through an Attribute Wrangle SOP node, connected to the FLIP Source node’s fourth input. You can find an example with a workflow description under Point variable density: multi-density.

Surface tension flattens irregular features and pulls water into droplets. It is useful for small-scale simulations where the effect of surface tension is often more important than gravity in controlling the dynamics. For large values, additional solver substeps are often required to ensure stability.

The value of the fluid’s surface tension. Note that high values often require additional solver substeps to ensure stability.

This option smoothes forces and helps to reduce artefacts with high Surface Tension settings.

The amount of blurring, when Enable Surface Tension Blur is on. Higher values give smoother results, but you might lose detail as well.

Turn on the viscosity solver.

When turned on, viscosity can be defined per point to create fluids with spatial viscosity.The viscosity values have to be defined separately, e.g. through an Attribute Wrangle SOP node, connected to the FLIP Source SOP node’s fourth input. You can find an example with a workflow description under Point variable visosity: honey.

This is the uniform viscosity value for the entire fluid. With FLIP fluids, the default value for water is typically 0. Higher values create more viscous and rigid fluids, e.g. oil, honey, or tar.

Causes the collision velocity to match the fluid velocity when close to collision objects. This allows a viscous fluid to slide along the collision object.

The amount of fluid velocity to blend into the collision’s tangential velocity, where a value of 1 indicates fully matching the fluid velocity.

Compute the vorticity of the fluid velocity field and mix it into the vorticity attribute on the particles.

Add a unique ID attribute to each particle.

When turned on, the solver tracks the particles' age during simulation.

Compute the relative density of each particle. This attribute represents how many particles are present in the neighborhood of a given particle. Low values correspond to isolated particles, and high values correspond to tightly packed neighborhoods.

Creates a rest attribute, which can be used to track the position of the fluid over time. Turn this on to map noise or textures in the liquid shader.

Creates a rest2 attribute that is one back from the main rest attribute, allowing you to run longer simulations without popping by blending between the two attributes.

Number of frames before resetting the rest attributes.

Which frame the rest attributes will be reset on. If you are prerolling the simulation, delaying the rest attribute initialization until after the preroll will usually give a better result.

Enter the number of custom attributes you want to create for the fluid, or click the + and - buttons to control their number.

Enter the name of the attribute you want to create, e.g. temperature or Cd for color.

Choose the attribute’s data type from the drop-down menu.

This is the attribute’s background value. For scalars there is one field, vectors require three input values.

To create a custom attribute, attribute-field pairs have to be defined. By default, both names are the same. Turn on this option only if you really have to.