Notch Notch Manual 0.9.23
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Fluid FLIP Affector

Fluid FLIP Affector

Simulates fluid dynamics on Particles with FLIP simulations.



Method #

This node simulates fluid dynamics on a particle system using the FLIP (FLuid In Particle) or PIC (Particle In Cell) simulation methods. This is typically used to simulate smoke, gas and other fluid effects. This works by transferring particle forces to a grid, solving pressure forces on the grid and then transferring the resultant forces back to the particle system. This allows particles to affect each other and to move in a locally coherent manner. The simulation is stable, detailed and efficient.

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. The simulation may be switched from 3D to 2D, in which case one axis is dropped from the simulation.


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.

Solver ModeChoose how the solver is calculated.
  • PIC : Particle In Cell. A detailed but more noisy and explosive simulation.
  • FLIP : A less detailed but more stable simulation.
Velocity ScaleScale the strength of the affectors velocity on the particles.
Incoming Velocity ScaleScales the velocity of the particles before they go into the pressure solver.
RadiusAlter the outer radius at which the affector is no longer effective.
Simulation SpeedSpeed at which the simulation is played.
Depth SpreadFor 2D simuations - control the range at which the solver affects particles in the depth axis.
Surface TensionControl the amount of surface tension in the fluid solver.
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 WidthThe width of the grid in cells.
Grid HeightThe height of the grid in cells.
Grid DepthThe depth of the grid in cells.
Use 3D SolverToggle whether to use a 3D solver in calculating the fluid dynamics.
2D AxisIf 3D solver is turned off, the selected 2D axis is used.
Visualise SolverVisualise the fluid dynamics solver.
Fixed Solver Update FramerateToggle whether to use the fixed solver, or the legacy mode.
Blend WeightControl how much the affector has an effect on the particles.

These properties control how the flip simulation updates its fluid simulation.

Time Step Mode

Choose how the simulation update rate is calculated. FLIP simulations are sensitive to the update rate: different update rates change the simulation results, so it may be desirable to control it in order to achieve a deterministic simulation.

  • Fixed - use a fixed update frame rate as specified by the Update Frame Rate property. Perform a single simulation update per frame.
  • Running (Normal) - use the same time delta as the main render : which may vary frame by frame. Perform a single simulation update per frame.
  • Adaptive - use a fixed update frame rate as specified by the Update Frame Rate property. If the render time step is greater than the fixed update rate : perform multiple simulation steps in a frame to keep in sync with it - at the cost of slower processing.
Update Frame RateThe frame rate used for simulation updates in Fixed or Adaptive time step mode.
Num Update StepsThe number of simulation steps to take per frame. This allows the simulation to be performed with multiple small time steps rather than single large steps, which may give better quality.


NameDescriptionTypical Input
Bounds TransformControls the area of space covered by the FLIP simulation.Bounding Box
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