aillieo / easybehaviortree

A very simple behavior tree implementation including a creator and runtime codes

Easy Behavior Tree

A very simple behavior tree implementation, including:

1. Basic behavior tree functions in C# but independent of any Unity Engine codes;

2. A behavior tree can run totally without a GameObject;

3. A behavior tree creator with Unity Editor in which binary format behavior tree files can be generated;

4. Types of nodes, node parameters and blackboard data can be easily extended;

5. Debugging system including logger interfaces and node info fomatters;

Requirement

The project is created with Unity 2018.3.6f, any other older or newer versions are not tested at the moment;

Usage

Create new nodes

1. Create new node classes simply by extending the provided base types like NodeAction, NodeComposite, NodeCondition or NodeDecorator:

   using EasyBehaviorTree;
   [System.Serializable]
   public class NodeTest : NodeAction
   {
       // ...
   }

2. Implement or override the methods:

   public class NodeTest : NodeAction
   {
       public override void Cleanup()
       {
           // your cleanup logic
       }
   
       protected override BTState ExecuteTask(float deltaTime)
       {
           // your execute logic
   
           // ...
   
           return BTState.Success;
       }
   }

3. Add NodeParam attribute to a field of your class if you want it to be exposed and modified in Creator:

   public class NodeTest : NodeAction
   {
       [NodeParam]
       private int foo;
   
       [NodeParam]
       private float bar;
   
       // ...
   }

4. If your node field has a type that is not included in NodeParamConfig, you can simply add the type name in NodeParamConfig.asset and click Regenerate:

   

5. Custom icons can be assigned to your node classes if you add a NodeIcon attribute to the class with the path of icon asset as argument:

   [System.Serializable]
   [NodeIcon("Assets/icon_for_node_test.png")]
   public class NodeTest : NodeAction
   {
       // ...
   }

Create behavior trees

1. Create an empty prefab with the same name as your behavior tree;

2. Create new empty gameobjects under the root of your prefab and a NodeDefine component should be attached to every gameobject in the hierarchy:

   

3. The structure of the prefab will be the the structure of your behavior tree, that means every gameobject with NodeDefine will be converted to a corresponding behavior tree node;

4. Modify params of the nodes, change their names, or just add some description text in Unity inspector window;

5. Save the prefab and right click it, and then select 'CreateTreeAsset' to create a behavior tree asset:

   

6. The following is a prefab named BT_Hero in sample directory:

   

and the tree information with DefaultFormatter:

```
root(EasyBehaviorTree.NodeRepeater) {repeatTimes=100,ignoringFailure=False,oncePerTick=True}
-sel(EasyBehaviorTree.NodeSelector) {}
--seq(EasyBehaviorTree.NodeSequence) {}
---hasTar(HasTarget) {}
---sel(EasyBehaviorTree.NodeSelector) {}
----seq(EasyBehaviorTree.NodeSequence) {}
-----inRange(InAttackRange) {}
-----seq(EasyBehaviorTree.NodeSequence) {}
------atk(AttackTarget) {}
------wait(EasyBehaviorTree.NodeActionWait) {time=1}
----move(ApproachTarget) {}
--find(FindTarget) {}
```

Runtime operation

1. Load a binary behavior tree asset with BehaviorTree.LoadBehaviorTree to create a behavior tree instance:

       // string fullPath = ...
       BehaviorTree behaviorTree = BehaviorTree.LoadBehaviorTree(fullPath);

2. Restart should be called before you tick your behavior tree:

       behaviorTree.Restart();

3. Tick should be called every frame (or driven by other systems) and the delta time should be passed as argument;

       void Update()
       {
           behaviorTree.Tick(Time.deltaTime);
       }

4. You can listen the events like OnBehaviorTreeCompleted etc.;

       behaviorTree.OnBehaviorTreeCompleted +=
           (bt,st) => {
               Debug.Log("Tree completed with state = " + st);
           };

5. Run scene 'Sample' for more details:

   

   and hope you enjoy it 😄