Particles node
Particle Flock
GPU boids flocking force. Add inside a Particle System: each particle steers by Separation / Alignment / Cohesion relative to its neighbours within Radius. Builds a spatial grid and works at full GPU particle scale; stacks with emitters, fields and gravity.
Inputs
| Port | Type | Default |
|---|---|---|
| EnableTurns the flocking force off without removing it. Off leaves the particles to the emitters, fields and gravity alone. | bool | true |
| RadiusHow far each particle looks for flockmates. Negatives count as 0, and 0 switches the flock off entirely; roughly 0.2…1 gives a readable swarm. | float | 0.4 |
| SeparationHow hard a particle pushes away from crowding neighbours. Negatives count as 0; raise it for an airy swarm, drop it and the flock clumps. | float | 1.0 |
| AlignmentHow strongly a particle matches its neighbours' heading. Negatives count as 0; high values turn the swarm into one sweeping shoal. | float | 1.0 |
| CohesionHow strongly a particle steers toward the centre of its neighbours. Negatives count as 0; too much and the flock collapses into a ball. | float | 1.0 |
| Sep RadiusThe personal-space bubble inside which particles push apart. Negatives count as 0, and anything larger than Radius is pulled back down to it. | float | 0.2 |
| Max SpeedThe cruising speed the steering aims for, and the ceiling on how hard a particle may turn. Never below 0.0001; small values drift lazily, large ones look frantic. | float | 1.0 |
| StrengthOverall weight of the flocking force against everything else acting on the particles. Negatives count as 0, and 0 leaves the flock inert. | float | 1.0 |
| Max NeighborsHow many neighbours each particle may sample per frame — a cost ceiling, not a look knob. Negatives count as 0, and 0 means unlimited; the averages settle well before 64. | int | 64 |
| MaskConnect any image to say where flocking acts: bright areas flock, dark areas are left alone. A camera or segmentation feed works too. | image | 0 |
| Mask ModeWhich channel of the mask is read — Alpha, Red, Green, Blue or Luminance. Values outside the list are pulled to the nearest one. | int | 0 |
| Mask InvertSwaps the mask so flocking acts where the image is dark instead of bright. | bool | false |
| Mask BlurSoftens the mask edge so flocking fades in rather than switching on at a hard line. Clamped to 0…1, where 1 blurs about a tenth of the mask grid. | float | 0.15 |
| Mask ScaleHow large the mask image is laid over the render view; 1 fits it exactly. Never below 0.0001; above 1 the mask spills past the frame edges. | float | 1 |
| Live SourceRebuilds the mask every frame — turn it on for a camera or video feed, leave it off for a still image so the mask is built only once. | bool | false |
| Show MaskDraws the mask the GPU actually samples, so you can see where the flocking is strong. A preview aid, not part of the final look. | bool | false |
What It Does
Particle Flock turns a particle swarm into a flock. Using the same GPU spatial grid as Find Neighbors, every particle looks at its neighbours within Radius and steers by the three classic Reynolds boids rules. The force integrates alongside everything else — emitters, fields, gravity, drag, colliders, trails — so you can flock and add turbulence or attractors at the same time.
The Three Rules
| Rule | Behaviour |
|---|---|
| Separation | Steer away from close neighbours — avoids crowding (uses Sep Radius). |
| Alignment | Match the average heading of nearby particles — flocks move together. |
| Cohesion | Steer toward the local centre — keeps the flock together. |
Balance the three weights for different characters: high Cohesion + Alignment → tight schools; high Separation → loose, restless swarms. Max Speed sets the cruising speed the boids steer toward, and Strength scales the whole force.
Tips
- Combine with a Particle Field (turbulence or an attractor) for flocks that wander or are drawn to a point.
- Add Find Neighbors + Particle Lines alongside it to draw the flock as a living plexus web.
- Lower Radius for many small flocks; raise it for one big murmuration.
Open Particle Flock in the interactive catalog →
Particle Flock is one of 381 nodes in Grafit Pro.
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