> simulations

Particle

simulations/particle·v1.3.0

IN:1 OUT:1

SUMMARY

Particle is a GPU-accelerated particle-based solver that simulates fluids and granular materials by treating them as collections of interacting particles. Each particle carries physical properties like density, pressure, and velocity, and interacts with neighbors within a smoothing radius. The solver supports three material modes: Fluids-SPH for liquid simulations using Smoothed Particle Hydrodynamics, Fluids-PBF for Position Based Fluids, and Grains for granular materials like sand with repulsion and attraction forces.

The simulation computes particle interactions through neighbor searches within the smoothing radius, calculating density-based pressure forces to maintain target density and optional viscosity forces for fluid thickness. You control the physical behavior through parameters like target density (incompressibility), viscosity (fluid thickness), cohesion (particle stickiness), surface tension (droplet formation), and adhesion (sticking to surfaces). The solver uses substeps and iterations to improve stability and accuracy, with adjustable time scaling for slow-motion or accelerated effects.

Particle supports multiple collision types including ground planes, bounding boxes, arbitrary collision geometry, and volumetric container geometry for creating vessels. This makes Particle suitable for water splashes, pouring liquids, sand and debris, viscous fluids like honey, and interactive particle-based effects.

PARAMETERS

PAGEParticle

[+]Solver Mode	Solvermode	Switches between Simple and Advect modes.
Target Particles Update POP	Particlesupdatepop	Reference to a POP node downstream in the network. This reference will cause a feedback loop and re-injects the particles next frame.
[+]Material Mode	Materialmode	Simulation mode: Fluids for liquids with viscosity, Grains for granular materials.
Substeps	Substeps	Number of solver substeps per frame.
Iterations	Iterations	Solver iterations per substep for constraint satisfaction.
Time Scale	Timescale	Global time multiplier for simulation speed.
Time Step	Timestep	Read-only display of effective timestep, equal to 1/FPS of TouchDesigner.
Smoothing Radius	Smoothingradius	Interaction distance for neighbor particle forces.
[+]Distribution	Distribution	Neighbor distribution method for particle interactions.
Num Hash Buckets	Numhashbuckets	Number of hash buckets for spatial neighbor lookups.
Max Neighbors	Maxneighbors	Maximum neighbor count per particle for force calculations.
Initialize	Initializepulse	Pulse to reset simulation and spawn initial particles.
Start	Startpulse	Pulse to begin simulation from initialized state.
Play	Play	Toggle continuous simulation playback.
Step	Steppulse	Pulse to advance simulation by one frame while paused.

PAGEProperties

Target Density	Targetdensity	Rest density the solver tries to maintain. Enabled in Fluids-SPH and Fluids-PBF modes.
Pressure Multiplier	Pressuremulti	Scales pressure force magnitude. Enabled in Fluids-SPH mode.
Near Pressure Multiplier	Nearpressuremult	Scales near-field pressure forces for close-range particle repulsion. Enabled in Fluids-SPH mode.
Viscosity	Viscosity	Fluid thickness and resistance to flow. Enabled in Fluids-SPH and Fluids-PBF modes.
Cohesion	Cohesion	Particle attraction force creating sticky fluid behavior. Enabled in Fluids-PBF mode.
Surface Tension	Surfacetension	Force causing droplet formation and surface smoothing. Enabled in Fluids-PBF mode.
Adhesion	Adhesion	Particle sticking force to collision surfaces. Enabled in Fluids-PBF mode.
Repulsion Weight	Repulsionweight	Strength of particle-particle repulsion force for granular materials. Enabled in Grains mode.
Attraction Weight	Attractionweight	Strength of particle-particle attraction for clumping behavior. Enabled in Grains mode.

PAGECollisions

Enable Ground Collision	Enablegroundcollision	Enables infinite ground plane collision.
[+]Ground Position	Groundposition	XYZ position of ground plane.
Display Ground	Displayground	Visualizes ground plane in output.
Enable Bounding Box Collision	Enablebboxcollision	Enables box-shaped collision boundary from POP geometry.
Bounding Box	Bbox	A reference to a POP defining the bounding box collision bounds.
[+]Lower Bounds	Bboxlowerbounds	Toggle to enable lower bounding planes for XYZ axes.
[+]Upper Bounds	Bboxupperbounds	Toggle to enable upper bounding planes for XYZ axes.
Bounding Box Margin	Bboxmargin	Extra margin distance added to the bounding box collision boundary.
Display Bounding Box	Displaybbox	Visualizes bounding box collision geometry.
[+]Collision Type	Collisiontype	Selects the collision geometry type for constraining particle movement.
Solid	Solid	Treats the collision geometry as a solid volume, preventing particles from passing through.
Project	Project	Projects particles onto the surface of the collision geometry.
Collision POP	Collisionpop	Reference to a POP containing the collision geometry when using POP collision type.
Collision Offset	Collisionoffset	Offset distance from the collision surface to prevent z-fighting artifacts.
[+]Size	Size	Size of the box collision geometry.
[+]Radius	Radius	Radius of the collision geometry per axis.
Corner Radius	Cornerradius	Radius of rounded corners on the box collision geometry.
Collison TOP	Collisontop	Reference to a TOP texture used as the collision field for SDF and texture collision types.
Use Custom Bounds	Usecustombounds	Enables custom bounding box for the collision texture instead of using the texture's native bounds.

[+]Lower Bounds	Lowerbounds	Lower bounds of the collision volume in world space.
[+]Upper Bounds	Upperbounds	Upper bounds of the collision volume in world space.

PAGECollisions

[+]Transform Order	Xord	Sets the order of scale, rotate, and translate operations for the collision geometry transform.
[+]Rotate Order	Rord	Sets the order of rotation operations for the collision geometry transform.
[+]Translate	T	Translation of the collision geometry in world space.
[+]Rotate	R	Rotation of the collision geometry in degrees.
[+]Scale	S	Scale of the collision geometry per axis.
[+]Pivot	P	Pivot point for the collision geometry transform.
Uniform Scale	Scale	Uniform scale factor applied to the collision geometry.
Display Geometry	Displaygeo	Shows the collision geometry in the viewport for visualization.
[+]Display Color	Displaycolor	Display color for the collision geometry visualization.

PAGEForces

[+]Gravity	Gravity	Gravity force vector in world space.
Gravity Multiplier	Gravitymultiplier	Scales gravity force magnitude.
Velocity Damping	Velocitydamping	Global velocity decay per frame.
Collision Damping	Collisiondamping	Amount of velocity dampening applied when particles collide with collision geometry.
Static Threshold	Staticthreshold	Velocity threshold below which dynamic friction becomes static friction.
Dynamic Scale	Dynamicscale	Dynamic friction coefficient for moving particles.
Limit Acceleration	Limitacc	Clamps particle acceleration to prevent instability.
Max Acceleration	Maxacc	Maximum allowed acceleration magnitude.

PAGECommon

Free Extra GPU Memory

Freeextragpumem

Free memory that has accumulated when output memory has grown and shrunk.

INPUTS

Input 0 POP – Particles In

OUTPUTS

Output 0 POP – Particles Out