Forces¶

Force effects change velocity, damp motion, guide particles around a reference, or apply a triggered radial burst.

Where to find it¶

Lists: Effects > Add Effect... > Forces. Nodes: Pro Physics > Shift+A > Forces.

Force effects¶

All effects on this page are available in Lists and Nodes. In Lists, their position in the Effects stack controls evaluation order. In Nodes, the particle-stream links define that order. Mappable controls can be driven with Data Mapping in Lists or with compatible Field connections in Nodes.

Gravity¶

Applies the Force vector as constant acceleration. The default points down world Z at Earth-like gravity. Change the vector to select another world-space direction or animate/map it for nonuniform gravity.

Gravity does not choose a scene object or use that object's orientation. For attraction to a point, use Attractor instead.

Wind¶

Applies the Force vector as constant world-space acceleration, using the same model as Gravity. The horizontal default suits directional airflow or conveyor-like acceleration.

Add Drag after Wind to keep speed from building up indefinitely.

Turbulence¶

Samples a procedural field at each particle and adds irregular motion.

• Mode controls how the field is applied. Force can change both velocity direction and speed. Direction redirects motion while preserving particle speed.
• Noise Type selects Classic, Smooth, Billow, Ridged, Warped Flow, or Streaks. Billow produces folded regions, Ridged emphasizes sharper structures, Warped Flow bends the sampling domain at greater cost, and Streaks produces elongated motion.
• Strength controls the field's influence.
• Scale controls feature size. Higher values create larger motion structures.
• Speed controls how quickly the field changes over time. Zero creates a stationary field.
• Seed selects another deterministic pattern.
• Projection samples the full 3D field or restricts it to the XY, XZ, or YZ plane. A planar projection ignores the remaining coordinate.
• Octaves adds progressively finer noise layers.
• Lacunarity controls the frequency increase between octaves.
• Persistence controls how strongly finer octaves contribute.

Choose Direction when the existing speed profile must remain intact. Choose Force when turbulence should add or remove kinetic energy. First establish Scale and Strength, then add octaves only when finer detail is visible and necessary.

Curl Noise¶

Applies a curl field for circulating flow.

• Mode selects Force or Direction. Force changes speed and direction; Direction preserves speed while steering.
• Noise Type selects Classic Curl, Smooth Curl, Ridged Curl, or Warped Curl. Ridged Curl creates sharper flow structures. Warped Curl produces more complex paths at higher cost.
• Strength controls the steering or force magnitude.
• Scale controls the size of curls. Higher values create larger flow features.
• Speed animates the curl field. Zero keeps the field fixed in space.
• Seed selects another deterministic field.
• Projection uses 3D, XY-Plane, XZ-Plane, or YZ-Plane sampling.
• Octaves adds smaller-scale curl detail.
• Lacunarity controls the frequency step between octaves.
• Persistence controls the amplitude retained by each finer octave.

Start with one octave and tune Scale before adding detail. If particles accelerate too much, use Direction mode or place Drag later in the effect order.

Drag¶

Reduces existing particle velocity. Coefficient controls how quickly motion is damped; zero has no effect and larger values slow particles more aggressively.

Order matters when Drag is combined with forces. Drag after Wind, Turbulence, or Curl Noise damps the velocity those effects just produced. Drag before them leaves the newly added motion undamped until the next simulation step.

Attractor¶

Pulls particles toward an object's evaluated origin.

• Attractor Object supplies the attraction point. The effect does not run without it.
• Strength controls the force magnitude. Negative values repel instead of attract.
• Min Distance clamps the near-field calculation so particles close to the origin do not receive an unbounded force.
• Falloff selects Constant, Linear, or Inverse Square attenuation.

Use a larger Min Distance if particles become unstable near the center. Use Constant for uniform pull, Linear for an art-directable distance response, and Inverse Square for a gravity-like response with a stronger near field.

Vortex¶

Applies rotational force around a line through the Vortex Object origin.

• Vortex Object supplies the center. The effect does not run without it.
• Axis is interpreted in the object's local orientation and defines the rotation line.
• Strength controls rotational force and can reverse the direction by changing sign.
• Falloff selects Constant, Linear, or Inverse Square attenuation with distance.

Vortex applies a force and does not lock particles to a radius. Combine it with an Attractor when particles should spiral inward, or use Rotation in Position mode when a stable orbit is more important than force-based motion.

Rotation¶

Moves particles around the Rotation Object origin and its local Z axis.

• Mode chooses Force or Position. Force blends velocity toward circular motion and remains dynamic. Position creates the required kinematic velocity so particles hold their orbit with less drift.
• Angular Speed is measured in radians per frame.
• Reverse flips the rotation direction.
• Variation gives particles stable per-particle variation in angular speed.
• Attraction, available in Force mode, damps outward radial velocity to retain particles around the axis.
• Escape Velocity, available in Force mode, stops Attraction for a particle whose outward radial speed exceeds the threshold.

Position mode is appropriate for controlled turntables and rings. Force mode allows other effects to disturb the orbit. Lower Attraction or Escape Velocity when particles should be able to break away.

Strange Attractor¶

Guides particles through a mathematical chaotic system placed at an object's origin.

• Attractor Object positions the field. The effect does not run without it.
• Strength scales the force applied to particles.
• Time Scale controls how quickly the mathematical state evolves.
• Size controls the world-space size of the pattern.
• Speed Limit clamps particle speed to contain unstable trajectories.
• Type selects Lorenz, Rössler, Chen, Chua, Moore-Spiegel, Duffing, Aizawa, Burke-Shaw, Lotka-Volterra, Rikitake, or Rabinovich-Fabrikant.

The parameter box below Type shows the selected system's coefficients. These control its topology, stability and orbit as well as its overall strength.

Keep these defaults as a baseline, establish Size and Strength, and then change one coefficient at a time. Use Speed Limit if a coefficient change produces runaway motion. All displayed coefficients are available as Data Mapping targets for their corresponding attractor type, in addition to the shared Strength and Time Scale targets.

Explosion¶

Applies radial velocity from the affected particles' mass center or from a scene object. It supports scene-time and particle-age triggers, one-shot or continuous application, velocity replacement or addition, distance falloff, stable speed variation, and optional release from Surface Attach.

See Infection, Explosion and Limit for the complete timing, distance, and velocity controls.

Choosing related effects¶