Notch Notch Manual 0.9.23
 Light | Dark
SPH Affector

SPH Affector

Simulates fluid dynamics on Particles with an SPH simulation.



Method #

This node simulates fluid dynamics on a particle system using the SPH (Smoothed Particle Hydrodynamics) simulation method. This is typically used to simulate liquid effects. It solves a fluid simulation by locally solving pressure forces between a particle and others nearby. This allows particles to affect each other and to move in a locally coherent manner. SPH works well for liquid effects like water.

The solver takes into account both the position and velocity of particles and their neighbours. The Viscosity attribute is used to make the simulation behave as a thicker liquid. Surface Tension is used to keep particles together like droplets of water. The radius around each particle in which they interact with their neighbours is controlled using the Cell Size attribute. Larger cell sizes may result in a smoother simulation that increases performance demands. The simulation may be switched from 3D to 2D, in which case one axis is dropped from the simulation.

The grid resolution and size used for the pressure solver is key to the detail and performance of the resultant simulation. A higher resolution grid over a smaller area will give a more detailed simulation, but higher resolution grids are slower to process.


These properties control the 3D transforms of the node. Transforms will generally be inherited by child nodes, although they can be ignored through the Inherit Transform Channels attributes.

Position XMove along the local x-axis.
Position YMove along the local y-axis.
Position ZMove along the local z-axis.
Rotation HeadingRotate around the local y-axis.
Rotation PitchRotate around the local x-axis.
Rotation BankRotate around the local z-axis.
Scale XScale along the local x-axis.
Scale YScale along the local y-axis.
Scale ZScale along the local z-axis.

Toggle which transform channels should be inherited from the parent node. By default, all transforms will be inherited.

Position XToggle inheritance of the X Position from the parent.
Position YToggle inheritance of the Y Position from the parent.
Position ZToggle inheritance of the Z Position from the parent.
Rotation HeadingToggle inheritance of the Rotation Heading from the parent.
Rotation PitchToggle inheritance of the Rotation Pitch from the parent.
Rotation BankToggle inheritance of the Rotation Bank from the parent.
Scale XToggle inheritance of the X Scale from the parent.
Scale YToggle inheritance of the Y Scale from the parent.
Scale ZToggle inheritance of the Z Scale from the parent.
World Position OnlyInherit the world position from the parent only, rotation and scale will be ignored. Overrides above properties.
Inherit TimeToggle inheritance of time from the parent.

These properties control the core behaviours of the node.

WeightHow strong an effect has on the particles.
Cell SizeThe area around each particle that resists other particles from getting within a certain distance.
ViscosityThe viscosity of the fluid, where smaller values make it more gas-like and larger values make it thicker - more like treacle.
GravityHow strong gravity is on the particles.
Pressure ScaleScales the amount by which particles push apart from each other.
Rest DensityControls the base density of the fluid.
Surface TensionHow much the particles want to stay together at their surface.
Max ForceThe limit on the force applied to the particles as a result of the simulation.
DampeningThe amount particle forces are damped - so they decay over time, rather than moving constantly.
Area ScaleScales the area of space the simulation is processing.
ModeChoose how the fluid simulation is calculated.
  • SPH : Use smoothed-particle hydrodynamics to generate the fluid dynamics.
  • Position Based : Uses position based fluids, faster but less realistic.
  • Inter-Particle Force : Simply pushes particles away from their neighbours.
DimensionChoose whether the effect is 2d or 3d.
Life Effect CoeffsHow much the particles are affected by the affector at different stages of the particles life cycle. Values 1 and 2 are control points used to control a bezier curve between values 0 and 3.
Grid ResolutionThe resolution of the underlying grid used in neighbourhood searches.


NameDescriptionTypical Input
Grid Transform NodesERROR: Variable not found: {input-node-particles-grid-transform-node-description}ERROR: Variable not found: {input-node-particles-grid-transform-node-typical-input}
Affected EmittersChoose which particle emitters can be affected by the affector.Primitive Emitter
Procedural FalloffUse the distance field from a procedural system to vary how strong the affector is.Procedural Root
Transform ModifiersApply the transforms of another node to this node.Null
Target NodeModifiy the rotations of the node to always direct the z axis towards the input.Null
Local Transform OverrideApply the transforms of another node to this node, relative to its parent.Null