A wrapper of a complete POP Fluid simulation with a ground plane, with tools for easily adjusting velocity and visualized trajectory. @inputs

## Parameters

## Fluid

Particle Separation

The desired distance between nearby particles in the fluid.

Impulse Activation

Controls when particles spawn as a burst. A value of 0 means off, any other value means on.

Impulse Fluid Density

Scales how many particles get spawned when Impulse Activation is on. Particles spawned = Source size ** Particle Separation ** Density. A Density of 1 will use all available spawn points within the source.

Const. Activation

Will cause particles to spawn as long as this is on. A value of 0 means off, any other value means on.

Const. Fluid Density

Scales how many particles get spawned when Constant Activation is on. Particles spawned = Source size ** Particle Separation ** Density. A Density of 1 will use all available spawn points within the source.

Stiffness

Determines how closely Particle Separation will be matched.

Viscosity

Amount of velocity diffusion, creating a more coherent motion among nearby particles. This can also be considered the “thickness” of the fluid. Can become unstable at higher values.

Maximum Acceleration

The maximum acceleration that can be applied to the particles when applying Particle Separation and Tensile Strength. Lowering this parameter can help mitigate instabilities.

Tensile Radius

Tensile force causes particles to repel eachother to prevent clustering. This parameter determines the distance (as a fraction of the particles kernel radius) at which this force is equal to Tensile Strength.

Tensile Strength

Magnitude of repulsive forces applied to nearby particles.

Vorticity Confinement

Counteracts energy dissipation by maintaining vortices.

Bounce

The elasticity of the fluid.

Bounce Forward

The tangential elasticity of the fluid. If two objects with bounce forward 1.0 collide, their tangential motion will be affected only by fricion. If two objects of bounce forward 0.0 collide, their tangential motion will be matched.

Friction

The coefficient of friction of the fluid. A value of 0 means the fluid is frictionless.

Dynamic Friction Scale

An object sliding may have a lower friction coefficient than an object at rest. This is the scale factor that relates the two. It is a scale between 0 and 1.

Temperature

Temperature marks how warm or cool the fluid is. This is used in gas simulations for ignition points or for buoyancy computations.

Direction

Direction of Initial Velocity. Can be set here manually or with the vector handle.

Magnitude

A multiplier of the explosion force.

Variance

How much the force can vary.

Initial Velocity

The calculated velocity based on Direction multiplied by Magnitude, plus or minus variance.

Enable Gravity

When gravity is disabled, Initial Velocity will remain constant until collision.

Gravity

A constant acceleration in the given direction, the default being (0, -9.80665, 0).

Enable Explosion Force

Enables a radial force that pushes particles outward.

Spread

How much the force will radiate away from the explosion direction. If there is no explosion direction, a Spread value of 1 will cause the explosion will be equally radial.

Explosion Direction

The direction the explosion force will be directed towards. A value of (0, 0, 0) will be an equally radial force.

Source Wireframe

Display a wireframe representation of the source geometry.

## Ground Plane

Enable Ground Plane

The Ground Plane is a grid for the fluid to collide with.

Snap Ground Plane to Trajectory

Enabling this will cause the Ground Plane to be centered on the trajectory curve. Transforms of the Ground Plane will act as an offset from the snap location along the trajectory curve.

Distance

How far along the trajectory curve the Ground Plane will be snapped to. A value of 1 means the Ground Plane will snap to the tip of the arrow.

Orientation

Which axes the grid will be aligned with.

Rows

Vertical divisions on the grid.

Columns

Horizontal divisions on the grid.

Size

Size of the grid.

Grid Guide

This is a wireframe representation of the ground plane.

## Collision Object

Geometry can be connected to the 2nd input if a static object other than the ground plane is desired. Animated

Enable if your geometry has animations.

Display Geometry

Enable to display the static geometry.

## Visualization

Fluid Display Mode

How to display the fluid output. Displaying as Particles while adjusting parameters is recommended. Particles

Displays the fluid particles as they are in the POP simulation.

Surface VDB

Displays the fluid as a surface VDB.

Surface Polygons

Displays the fluid as full surface polygons (not polygon soup).

Voxel Scale

The voxel side length to use for the generated VDB volume. This is a scale on the Particle Separation length. For example, if Particle separation is 0.1 and Voxel size is 0.5, the side length of the voxels of the output field will be 0.05.

Influence Scale

The maximum distance at which particles interact. Small increases can give smoother results but increase the cooking time and memory usage greatly. This is a scale on the Particle Separation length. For example, if Particle Separation is 0.1 and Influence radius is 3, particles will interact if they are within 0.6 units of each other.

Droplet Scale

Must be smaller than Influence Scale.

Fluid Color

Color of fluid displayed in the viewport.

Dilate

Expands the surface of the fluid outward.

Smooth

Smooths the fluid surface using the selected method for the number of iterations.

Erode

Contracts the surface of the fluid inward.

Final Smooth

Smoothing performed after Erode and Dilate operations using the selected method for the number of iterations.

## Guides

Initial Velocity

Shows direction and magnitude of initial velocity without gravity.

Show Trajectory

Trajectory based on timeline.

Trajectory Curve

This shows the calculated trajectory based on the initial velocity and gravity force. Does not factor in explosion force.

Length

Timeline

Trajectory length is based on the local variables $RFSTART and $RFEND.

Manual Time

Use the Time parameter to generate the length of the trajectory.

Time

Time in seconds to calculate the length of the trajectory.

## Solver

Time Scale

A multiplier for time within the simulation.

Min Substeps

The minimum number of calculations to perform between frames.

Max Substeps

The maximum number of calculations to perform between frames. A higher number of substeps will produce more accurate results at the cost of simulation time.

Enable Auto Sleep

Enabling will cause the fluid to freeze when it dips below a threshold for movement.