Forces guide
Browse Forces controls by UI section
The FORCES controls move particles after birth. Use them on the selected system to bend paths, create flow, or bring particles back toward their starting points. Entropy applies forces automatically as simulation time advances.
A force changes motion over time. A displacement changes the drawn position without permanently changing that motion. Use forces for drifting paths. Use displacements for a shape that must come apart and return.
Choose a force
| Force | Effect |
|---|---|
| Gravity | Constant vertical acceleration. Positive values make particles fall; negative values lift them. |
| Buoyancy | Lift that fades as particles cool. It needs aging particles. |
| Drag | Reduces velocity over time. |
| Wind | Pushes continuously along X, Y, and Z. |
| Turbulence | Bends motion with an evolving curl field. |
| Vortex | Spins particles around an axis and can pull them toward it. |
| Attractor | Pulls toward a target. Negative strength pushes away. |
| Spring | Pulls particles toward their birth positions. Damping reduces bouncing. |
Set one force at a time so you can see its effect.
Turbulence Scale controls the size of swirls: higher values make finer motion. Speed controls pattern evolution. Octaves adds finer layers. Fade In delays full turbulence for newborn particles; Static emission does not use this age-based fade.
Vortex strength sets spin. Pull sets attraction toward the axis. A negative value reverses each effect. Vortex Anchor selects whether the center follows the emitter or uses an absolute scene position.
Attractor can use up to eight After Effects Light layers whose names start with Attractor. Composer cannot preview those composition lights; enabling this option removes its manual attractor preview.
Reversible motion
Fractal Noise Displacement offsets particles with layered noise. Disperse scatters them along stable random directions. Return either strength to zero to remove that offset.
Movement offsets released particles along X, Y, and Z. Oscillate creates repeating wave motion or random shimmer. A wave's frequency controls cycles per second; wavelength controls distance between crests.
Displacement can also affect size, opacity, and hue. Its size effect works even with displacement strength at zero. The opacity effect only dims particles; it does not exceed the base opacity.
Returning a displacement to zero removes that displacement. If forces also moved the particles, their simulated positions can still have changed.
Release particles with Force Mapping
Force Mapping uses a pattern to hold or release particles. The pattern can come from an editable graph or an After Effects layer's alpha channel. Each particle reads the map at its birth position, so its place in the map stays fixed as it moves.
Amount in Force Mapping controls how strongly the map gates Wind, Turbulence, Vortex, and Attractor. At full amount, low or transparent regions hold particles and high or opaque regions release them.
For a graph-driven breakup:
- Create a Static Text or Mesh system.
- Choose Graph as the Force Mapping source and raise Amount to full.
- Choose the map axis that crosses the shape in the desired direction.
- Set Dissolve to -1 to hold the particles.
- Add Disperse and use Affect Disperse to suppress it while particles are held.
- Animate Dissolve toward +1 in After Effects.
- Preview the transition. The shape should release across the chosen axis.
Feather controls the width of the release band. Stagger gives particles separate release moments within that band. Reverse mirrors the curve. Affect Size, Opacity, and Hue change the appearance during release. Negative size or opacity affects can bring a second system into view where the first disappears.
Release Kills ends each particle at the selected release threshold. This can trigger an On Parent Death child, including from a Static source. Erode Body dissolves a visible text or mesh body across the same band.
Graph-source Delay postpones mapped appearance and displacement changes after release. Composer previews the graph source. Layer-source maps and map inversion require an After Effects check.
Time and keyframes
A keyframe stores a control value at a particular time in After Effects. Use keyframes there to animate changes such as source position or Dissolve.
Physics Time Scale changes simulation speed for every system on the layer. Zero freezes motion without clearing the current frame. Pre-run simulates time before frame zero so the first visible frame can contain an established stream.
Composer imports a snapshot of an animated layer. Inspect any keyframe warning when you apply it back. See presets and After Effects.
---