pFriction

pFriction is a Fusion particle modifier that applies resistance to existing motion. It is placed after pEmitter or other force/modifier nodes and before pRender, receiving an existing particle stream and progressively reducing linear and/or rotational velocity.

Velocity Friction acts on particle Velocity. Higher values create stronger resistance and make particles lose speed more quickly. It is not an instantaneous Stop and does not define a new direction; it damps motion that already exists.

Spin Friction separately acts on Rotation/Spin. A particle can lose translational speed while continuing to rotate, or keep moving while its rotation settles, so Velocity and Spin Friction should be tuned independently.

pFriction is especially useful after pDirectionalForce, pTurbulence, pVortex and other tools that create or alter velocity. Forces add or redirect motion; pFriction removes energy from that motion and helps the system settle.

Random Seed/Randomize control reproducible random behavior used by the particle calculation. Keep the seed fixed while tuning friction so a new random sample does not hide the effect of Velocity or Spin Friction.

Conditions Probability limits the chance of the behavior being applied. Like other particle nodes, Probability is evaluated for each particle on each frame; 0.6 is not one permanent 60-percent subset for the full lifespan.

Start/End Age uses normalized particle lifespan rather than timeline frame numbers. For example, 0.5–1.0 leaves the first half of a particle life free and enables damping only later.

Set Mode and Set 1–32 filter particle Sets that were assigned upstream by tools such as pEmitter, pImageEmitter, pChangeStyle or pSpawn. pFriction does not assign those Sets itself.

Region Mode and Region are different controls. Region Mode defines the condition relative to an area—ignore, intersecting, inside, not intersecting, not inside, entering or leaving—while Region selects the geometry itself.

All, Bezier, Cube, Line, Rectangle and Sphere are built-in Regions. They are generated inside pFriction and require no second cable, so pEmitter → pFriction → pRender remains valid with a built-in spatial gate.

Bitmap and Mesh are exceptions: selecting either creates an additional dynamic Region input. Bitmap accepts a 2D image/selectable channel and Mesh accepts a 3D mesh. This is Region data, not an Effect Mask or particle stream.

Mesh Region uses the common particle Region controls for surface/volume interpretation, winding behavior and ObjectID filtering. These controls define the spatial gate, not the strength of friction.

Line Region is defined by two XYZ points; Rectangle remains planar while Cube, Sphere and Mesh provide volumetric 3D regions. In a 3D system verify Z position rather than judging only the X/Y projection.

A Region can act like a local viscous medium: particles move freely outside, lose Velocity and Spin while eligible inside, and leave with their already reduced motion. This behavior must be judged in playback rather than from one still frame.

pFriction does not attract particles or choose a travel direction. Use a force node to accelerate or redirect particles and pFollow or point-like forces for a target; pFriction only damps existing Velocity and Spin.

The pFriction output remains Particles data. A visible RGBA image appears only downstream through pRender, after which ordinary image processing and MediaOut can be used.

Friction should be evaluated over time. Small values may be subtle on adjacent frames but accumulate over dozens of frames, while excessive values can remove motion too quickly. Compare the same playback range and change one control at a time.