libgdx-gdx-ai

libGDX gdx-ai Extension

Reference for steering behaviors, A* pathfinding, behavior trees, finite state machines, and scheduling in the gdx-ai extension.

Dependency

// In core module only — pure Java, no native dependencies
implementation "com.badlogicgames.gdx:gdx-ai:$aiVersion"

Works on all backends including headless. No platform-specific jars needed.

Steering Behaviors

Steerable Interface

Steerable<T extends Vector<T>> extends Location<T> and Limiter. Your entity implements it, providing: getPosition(), getOrientation(), setOrientation(), newLocation(), vectorToAngle(), angleToVector(), getLinearVelocity(), getAngularVelocity(), getBoundingRadius(), isTagged()/setTagged(), and all Limiter getters/setters for max linear/angular speed/acceleration.

vectorToAngle/angleToVector convention: vectorToAngle(v) = atan2(-v.x, v.y), angleToVector(out, a) sets out.x = -sin(a), out.y = cos(a). Getting this wrong causes steering to point in the wrong direction.

SteeringAcceleration — The Output Container

SteeringAcceleration<T> has public fields T linear and float angular. Create ONE per entity, reuse each frame: new SteeringAcceleration<>(new Vector2()).

calculateSteering() only fills the output container — it does NOT move the entity. You must apply the acceleration to velocity and position yourself each frame.

Common Setup Pattern

// 1. Create behavior — target via constructor or setter
Arrive<Vector2> arrive = new Arrive<>(steerable, targetLocation)
    .setArrivalTolerance(0.5f)        // stop within this distance
    .setDecelerationRadius(3f)        // start slowing here
    .setTimeToTarget(0.1f);           // response speed (lower = snappier)
// Or set target separately:
// Arrive<Vector2> arrive = new Arrive<>(steerable)
//     .setTarget(targetLocation)
//     ...;

// 2. Each frame — calculate then apply
arrive.calculateSteering(steeringOutput);
linearVelocity.mulAdd(steeringOutput.linear, deltaTime);
if (linearVelocity.len2() > maxLinearSpeed * maxLinearSpeed)
    linearVelocity.setLength(maxLinearSpeed);
position.mulAdd(linearVelocity, deltaTime);