Splatter.AI

Splatter.AI is a code based behaviour tree for Unity projects. Requires Unity 6 (6000.0 or newer).

Installation

To add to your Unity project go to the Package Manager, click the plus in the top left of the window. Select git URL and enter: https://github.com/ormesam/splatter.ai.git?path=/src/Assets/Splatter.AI

The package itself has no dependencies. The samples additionally need com.unity.ai.navigation.

Quick Start

1. Create new class deriving from BehaviourTreeRunner, which is a MonoBehaviour
2. Override CreateRoot method, here you can build up your behaviour tree as shown below - composites take a collection initialiser, decorators take a Child
3. Override Awake method (optional) and initiate blackboard values, make sure to call base.Awake(); at the start of the method as that is what creates Tree
4. Attach the script to the GameObject, and set Tick Interval in the inspector if the tree does not need to run every frame
5. On Start the tree registers itself with BehaviourTreeManager and is ticked centrally from then on. Disabling the component pauses the tree in place; re-enabling resumes it

See REFERENCE.md for the node reference, reactivity and abort modes, ticking, the behaviour tree viewer, and tests.

Example

An enemy that wanders until it sees the player, chases while it can see them, and returns to wandering when it loses them.

using Splatter.AI;
using Splatter.AI.Composites;
using Splatter.AI.Decorators;
using Splatter.AI.Leaves;
using Splatter.AI.Unity;
using UnityEngine;

public class Zombie : BehaviourTreeRunner {
    private const string PlayerVisibleKey = "PlayerVisible";

    public GameObject Player;
    public float SightRange = 10f;

    private void Update() {
        // Sensors can write every frame; observers are only notified when the value changes.
        Tree.Blackboard[PlayerVisibleKey] = CanSeePlayer();
    }

    protected override Node CreateRoot() {
        return new Repeater {
            Child = new Selector {
                new BlackboardObserverDecorator(Tree.Blackboard, PlayerVisibleKey, true, AbortMode.Both) {
                    Child = new Leaf("Chase player", ChasePlayer),
                },
                new Sequencer("Wander") {
                    new Leaf("Pick a spot", PickSpot),
                    new WaitNode("Pause", 1f, 3f),
                },
            },
        };
    }

    private NodeResult ChasePlayer() {
        // Move towards the player; never finishes on its own.
        return NodeResult.Running;
    }

    private NodeResult PickSpot() {
        return NodeResult.Success;
    }

    private bool CanSeePlayer() {
        return Vector3.Distance(transform.position, Player.transform.position) < SightRange;
    }
}

Patrol / Chase Demo

Found under Samples, in Samples/Scenes/PatrolDemo.unity. Samples/Scripts/PatrolChaseEnemy.cs is the tree.

Video.mp4