tools-unity-behavior-designer

Behavior Designer

Overview

Behavior Designer is a behavior tree implementation for Unity AI. This skill covers patterns for creating robust AI behaviors for enemies, NPCs, and game entities.

When to Use

• Enemy AI behavior
• NPC decision making
• Boss fight patterns
• Companion AI
• Any complex state-based AI

Core Concepts

Behavior Tree Structure

Selector (OR logic - first success wins)
├── Sequence (AND logic - all must succeed)
│   ├── Conditional (check condition)
│   └── Action (do something)
├── Sequence
│   ├── Conditional
│   └── Action
└── Action (fallback)

Custom Tasks

Action Task

using BehaviorDesigner.Runtime;
using BehaviorDesigner.Runtime.Tasks;

[TaskCategory("Combat")]
[TaskDescription("Attacks the current target")]
public class AttackTarget : Action
{
    [Tooltip("Reference to the ability system")]
    public SharedGameObject abilitySystemOwner;
    
    [Tooltip("The ability to activate")]
    public SharedString abilityTag;
    
    [Tooltip("Target to attack")]
    public SharedGameObject target;
    
    private IAbilitySystem _abilitySystem;
    private bool _abilityStarted;
    
    public override void OnStart()
    {
        _abilityStarted = false;
        
        if (abilitySystemOwner.Value == null)
        {
            Debug.LogError("AttackTarget: No ability system owner");
            return;
        }
        
        _abilitySystem = abilitySystemOwner.Value.GetComponent<IAbilitySystem>();
    }
    
    public override TaskStatus OnUpdate()
    {
        if (_abilitySystem == null || target.Value == null)
        {
            return TaskStatus.Failure;
        }
        
        if (!_abilityStarted)
        {
            if (!_abilitySystem.TryActivateAbilityByTag(abilityTag.Value))
            {
                return TaskStatus.Failure;
            }
            _abilityStarted = true;
        }
        
        // Check if ability is still running
        if (_abilitySystem.IsAbilityActive(abilityTag.Value))
        {
            return TaskStatus.Running;
        }
        
        return TaskStatus.Success;
    }
    
    public override void OnEnd()
    {
        // Cleanup if interrupted
        if (_abilityStarted && _abilitySystem != null)
        {
            _abilitySystem.CancelAbilityByTag(abilityTag.Value);
        }
    }
}