---
title: "Steering Behaviours and Flocking"
package: "@phaser-ae/steering"
tier: Free
version: 3.0.0-5
released: 2026-10-14
updated: 2026-10-19
description: "Agents that decide where to go by blending behaviours into one force, to seek, flee, wander, flock, avoid, follow paths, navigate routes and ride flow fields, in 2D or 3D."
url: https://phaser.io/packs/steering
site: Phaser - https://phaser.io
---

# Steering Behaviours and Flocking

Agents that decide where to go on their own: birds that flock, fish that scatter from a shark, guards that patrol round
pillars, a horde pouring along a flow field. Each is a position, a velocity and a list of behaviours, blended every
fixed step into one force, in a 3D world or on a 2D one.

## What it does

You spawn an agent with a config: a top speed, a force budget, a mass and a list of behaviours, each with its own
tuning, a `weight` and a `priority`. Each fixed step the agent works through its behaviours, highest priority first, and
each claims part of the force budget. Avoidance, terrain, ceiling, containment and edges come first, flocking and
following a leader next, goals last, and once the budget is spent the rest get nothing. That ordering is what stops a
flock steering into a wall to keep up with its neighbours.

Bind an agent to a render handle and it writes its pose each step, interpolated between fixed steps, with yaw and pitch
turning towards its velocity and an optional bank into turns. Ground walkers keep their height on a ground function and
can pitch with the slope; flyers and swimmers steer in all three axes. Or read `agent.pos` and use it however you like:
the pack holds no roster objects and draws nothing, so it runs in a worker or a test exactly as it does in a frame.

Beyond single behaviours, attractors and repulsors pull or scatter whole regions, and a strong repulsor push makes
agents panic and run faster for a while, which is how a shoal bolts from a shark. `navigate` steers along a route
planned by `nav` or `nav-mesh`, re-planning as the target moves, and `flow` follows a flow field, for hundreds of
walkers heading to one place. Every wander draws from the agent's own stream, forked from the game's seeded one, so a
replay wanders exactly as the first run did.

## Features

- **Seventeen behaviours** — seek, flee, arrive, pursue, evade, wander, follow, flock, avoid, terrain, ceiling,
  contain, edge, leader, navigate, flow and custom.
- **Priority blending** — behaviours claim a force budget highest priority first, so staying safe wins over goals.
- **Boids flocking** — separation, alignment and cohesion over the nearest neighbours, with a spatial hash above 40
  agents.
- **Fields and obstacles** — attractors and repulsors that can follow a live object, panic after a strong push, and
  sphere and box obstacles.
- **Planned routes** — `navigate` over any planner with a path method, sized for the agent's body, turning for the next
  waypoint as soon as it can reach it directly.
- **Flow fields** — `flow` follows `nav`'s flow field, its weighted grid adapted by a function, or any field you write.
- **Ground and flight** — height held to a ground function with optional slope pitch, or full 3D movement with a pitch
  clamp and banking.
- **Six presets** — `firefly`, `fish`, `shoal`, `hunter`, `bird` and `patrol`.
- **2D agents** — `spawn2d` and `flock2d` drive a sprite's `x`, `y` and `rot` with the same behaviours in 2D.
- **Seeded and replayable** — per-agent streams forked from the game's, with snapshot and restore.

## Good for

- **Flocks, shoals and swarms**: birds, fish and fireflies that move as groups and scatter from a predator.
- **Patrolling guards** in a stealth game, following routes round a tile map or over 3D terrain.
- **Hordes and crowds** pouring along a flow field to one goal, such as a tower-defence wave or a zombie rush.
- **Homing missiles and hunters** that pursue a moving target and aim for where it will be.
- **Wildlife and ambience**: wandering animals and insects that bring a world to life.
- **Escorts and followers** that keep station behind a leader.

## Make it yours

Every agent is its config and every behaviour its tuning. The config sets `maxSpeed`, `maxForce`, `mass`, `turnRate`,
`maxPitch`, `bank`, `panicSpeed`, a `ground`, a `seed`, the `handle` to drive, and `tickEvery` to solve steering only
every nth step, for level of detail; each behaviour has its own distances, a `weight` and a `priority`. Presets are a
starting point to override, and a `custom` behaviour adds a force of your own.

Two different uses: a 3D underwater scene where a shoal flocks with a little wander, and a repulsor following the shark
makes it panic and bolt at its panic speed; and a top-down 2D stealth game where a guard sprite avoids obstacles and
navigates a `nav` grid towards the hero, re-planning as the hero moves, while a flock of birds wanders overhead.

## A quick look

A 2D guard that navigates towards the hero, a school of fish, and a shark they flee:

```ts
const grid = game.nav.grid2d({ cols: 20, rows: 12, cell: 32, walkable });
const guard = game.steering.spawn2d({
    handle: guardSprite, pos: { x: 48, y: 48 }, maxSpeed: 140, maxForce: 700,
    behaviors: [{ kind: 'avoid' }, { kind: 'navigate', grid, target: () => ({ x: hero.x, y: hero.y }), radius: 10 }],
});
const fish = game.steering.flock2d({ maxSpeed: 90, maxForce: 300,
    behaviors: [{ kind: 'flock', radius: 48 }, { kind: 'wander', weight: 0.4 }] }, fishSprites);
game.steering.agents2d.repulsor({ follow: shark, radius: 120, strength: 2000 });
```

## Works with

- `nav` — the grids that planned routes run over, and the flow fields hordes follow.
- `nav-mesh` — routes over bridges, arches and floors above floors; its own crowd is a separate avoidance system, so
  use one or the other for a given crowd.
- `path-3d` — smooth 3D curves for agents to follow.
- `actors` — lighter one-call movement chips for a 2D arcade shooter.
- `track` — authored routes with junctions, when the way is fixed rather than steered.
- `stealth` — sight, hearing and suspicion for the guards you steer.

## Good to know

- Agents do not collide with each other: separation keeps them apart, which reads right for crowds but is no
  solid-body guarantee.
- `avoid` sees only the obstacles you give the system, on the ground plane; it does not avoid other agents or walls it
  has not been told about.
- A steered body swings a little wide of sharp turns by its own momentum, so pair `navigate` with `avoid` or collision
  where contact matters.
- 2D agents have no `terrain` or `ceiling`, and 2D and 3D agents are separate systems that never flock together.
- It moves a handle but does not animate it: how the body looks while moving is your game's.

---

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