The following is a pure code reference, without the node editing and export configuration of the Unity plug-in. The concept of behavior tree and various Unity plug-ins are not introduced here. The code is summarized and refined based on Unity's 2D Game Kit, which will be very helpful for learning and understanding behavior trees!
using BTAI;
using UnityEngine;
public class TestBT : MonoBehaviour, BTAI.IBTDebugable
{
Root aiRoot = BT.Root();
private void OnEnable()
{
aiRoot.OpenBranch(
BT.If(TestVisibleTarget).OpenBranch(
BT.Call(Aim),
BT.Call(Shoot)
),
BT.Sequence().OpenBranch(
BT.Call(Walk),
BT.Wait(5.0f),
BT.Call(Turn),
BT.Wait(1.0f),
BT.Call(Turn)
)
);
}
private void Turn()
{
Debug.Log("执行了 Turn");
}
private void Walk()
{
Debug.Log("执行了 Walk");
}
private void Shoot()
{
Debug.Log("执行了 Shoot");
}
private void Aim()
{
Debug.Log("执行了 Aim");
}
private bool TestVisibleTarget()
{
var isSuccess = UnityEngine.Random.Range(0, 2) == 1;
Debug.Log("执行了 TestVisibleTarget Result:" + isSuccess);
return isSuccess;
}
private void Update()
{
aiRoot.Tick();
}
public Root GetAIRoot()
{
return aiRoot;
}
}![C#/implementation steps based on Unity behavior tree [Pure code]](https://img.php.cn//upload/image/166/383/356/1532573069628719.png "1532573069628719.png")
using System.Collections.Generic;
using UnityEngine;
/// <summary>
/// 这只是脚本系统
/// 行为树会从Root节点开始遍历子节点。Update中执行
/// 每个节点都有相关的操作，但是基本上就是返回三种状态
/// ● Success: 节点成功完成任务
/// ● Failure: 节点未通过任务
/// ● Continue:节点尚未完成任务。
/// 但是每个节点的父节点对子节点的结果处理方式还不同。 例如
/// ● Test 节点： 测试节点将调用其子节点并在测试为真时返回子节点状态，如果测试为假，则返回Failure而不调用其子节点。
/// 行为树的一种构造方式如下：
/// Root aiRoot = BT.Root();
/// aiRoot.Do(
/// BT.If(TestVisibleTarget).Do(
/// BT.Call(Aim),
/// BT.Call(Shoot)
/// ),
/// BT.Sequence().Do(
/// BT.Call(Walk),
/// BT.Wait(5.0f),
/// BT.Call(Turn),
/// BT.Wait(1.0f),
/// BT.Call(Turn)
/// )
/// );
///然后在Update中 调用 aiRoot.Tick() 。 刚刚构造的行为树是怎么样的检查过程呢？
///1、首先检查TestVisibleTarget是否返回Ture，如果是继续执行子节点执行Aim函数和Shoot函数
///2、TestVisibleTarget是否返回false,if节点将返回Failure， 然后Root 将转向下一个子节点。这是个Sequence节点，它从执行第一个子节点开始。
/// 1）将调用Walk函数，直接返回 Success，以便Sequence将下一个子节点激活并执行它。
/// 2）执行Wait 节点，只是要等待5秒，还是第一次调用，所以肯定返回Running状态， 当Sequence从子节点上得到Running状态时，不会更改激活的子节点索引，下次Update的时候还是从这个节点开始执行
///3、Update的执行，当Wait节点等待的时间到了的时候，将会返回Success， 以便序列将转到下一个孩子。
///脚本中的Node列表
/// Sequence：
//一个接一个地执行子节点。如果子节点返回：
//●Success：Sequence将选择下一帧的下一个孩子开始。
//●Failure：Sequence将返回到下一帧的第一个子节点（从头开始）。
//●Continue：Sequence将在下一帧再次调用该节点。
//RandomSequence：
// 每次调用时，从子列表中执行一个随机子节点。您可以在构造函数中指定要应用于每个子项的权重列表作为int数组，以使某些子项更有可能被选中。
//Selector ：
//按顺序执行所有子项，直到一个返回Success，然后退出而不执行其余子节点。如果没有返回Success，则此节点将返回Failure。
// Condition ：
// 如果给定函数返回true，则此节点返回Success;如果为false，则返回Failure。
// 与其他依赖于子节点结果的节点链接时很有用（例如，Sequence，Selector等）
// If ：
//调用给定的函数。
// ●如果返回true，则调用当前活动的子级并返回其状态。
// ●否则，它将在不调用其子项的情况下返回Failure
// While：
//只要给定函数返回true，就返回Continue（因此，下一帧将再次从该节点开始，而不会评估所有先前的节点）。
//子节点们将陆续被执行。
//当函数返回false并且循环中断时，将返回Failure。
// Call
//调用给定的函数，它将始终返回Success。是动作节点！
//Repeat
//将连续执行给定次数的所有子节点。
//始终返回Continue，直到达到计数，并返回Success。
//Wait
//将返回Continue，直到达到给定时间（首次调用时开始），然后返回Success。
//Trigger
//允许在给定的动画师animator中设置Trigger参数（如果最后一个参数设置为false，则取消设置触发器）。始终返回成功。
//SetBool
//允许在给定的animator中设置布尔参数的值。始终返回成功
//SetActive
//设置给定GameObject的活动/非活动状态。始终返回成功。
/// </summary>
namespace BTAI
{
public enum BTState
{
Failure,
Success,
Continue,
Abort
}
/// <summary>
/// 节点 对象工厂
/// </summary>
public static class BT
{
public static Root Root() { return new Root(); }
public static Sequence Sequence() { return new Sequence(); }
public static Selector Selector(bool shuffle = false) { return new Selector(shuffle); }
public static Action RunCoroutine(System.Func<IEnumerator<BTState>> coroutine) { return new Action(coroutine); }
public static Action Call(System.Action fn) { return new Action(fn); }
public static ConditionalBranch If(System.Func<bool> fn) { return new ConditionalBranch(fn); }
public static While While(System.Func<bool> fn) { return new While(fn); }
public static Condition Condition(System.Func<bool> fn) { return new Condition(fn); }
public static Repeat Repeat(int count) { return new Repeat(count); }
public static Wait Wait(float seconds) { return new Wait(seconds); }
public static Trigger Trigger(Animator animator, string name, bool set = true) { return new Trigger(animator, name, set); }
public static WaitForAnimatorState WaitForAnimatorState(Animator animator, string name, int layer = 0) { return new WaitForAnimatorState(animator, name, layer); }
public static SetBool SetBool(Animator animator, string name, bool value) { return new SetBool(animator, name, value); }
public static SetActive SetActive(GameObject gameObject, bool active) { return new SetActive(gameObject, active); }
public static WaitForAnimatorSignal WaitForAnimatorSignal(Animator animator, string name, string state, int layer = 0) { return new WaitForAnimatorSignal(animator, name, state, layer); }
public static Terminate Terminate() { return new Terminate(); }
public static Log Log(string msg) { return new Log(msg); }
public static RandomSequence RandomSequence(int[] weights = null) { return new BTAI.RandomSequence(weights); }
}
/// <summary>
/// 节点抽象类
/// </summary>
public abstract class BTNode
{
public abstract BTState Tick();
}
/// <summary>
/// 包含子节点的组合 节点基类
/// </summary>
public abstract class Branch : BTNode
{
protected int activeChild;
protected List<BTNode> children = new List<BTNode>();
public virtual Branch OpenBranch(params BTNode[] children)
{
for (var i = 0; i < children.Length; i++)
this.children.Add(children[i]);
return this;
}
public List<BTNode> Children()
{
return children;
}
public int ActiveChild()
{
return activeChild;
}
public virtual void ResetChildren()
{
activeChild = 0;
for (var i = 0; i < children.Count; i++)
{
Branch b = children[i] as Branch;
if (b != null)
{
b.ResetChildren();
}
}
}
}
/// <summary>
/// 装饰节点 只包含一个子节点，用于某种方式改变这个节点的行为
/// 比如过滤器（用于决定是否允许子节点运行的，如：Until Success, Until Fail等），这种节点的子节点应该是条件节点，条件节点一直检测“视线中是否有敌人”，知道发现敌人为止。
/// 或者 Limit 节点，用于指定某个子节点的最大运行次数
/// 或者 Timer节点，设置了一个计时器，不会立即执行子节点，而是等一段时间，时间到了开始执行子节点
/// 或者 TimerLimit节点，用于指定某个子节点的最长运行时间。
/// 或者 用于产生某个返回状态，
/// </summary>
public abstract class Decorator : BTNode
{
protected BTNode child;
public Decorator Do(BTNode child)
{
this.child = child;
return this;
}
}
/// <summary>
/// 顺序节点 （从左到右依次执行所有子节点，只要子节点返回Success就继续执行后续子节点，直到遇到Failure或者Runing，
/// 停止后续执行，并把这个节点返回给父节点，只有它的所有子节点都是Success他才会向父节点返回Success）
/// </summary>
public class Sequence : Branch
{
public override BTState Tick()
{
var childState = children[activeChild].Tick();
switch (childState)
{
case BTState.Success:
activeChild++;
if (activeChild == children.Count)
{
activeChild = 0;
return BTState.Success;
}
else
return BTState.Continue;
case BTState.Failure:
activeChild = 0;
return BTState.Failure;
case BTState.Continue:
return BTState.Continue;
case BTState.Abort:
activeChild = 0;
return BTState.Abort;
}
throw new System.Exception("This should never happen, but clearly it has.");
}
}
/// <summary>
/// 选择节点从左到右依次执行所有子节点 ，只要遇到failure就继续执行后续子节点，直到遇到一个节点返回Success或Running为止。向父节点返回Success或Running
/// 所有子节点都是Fail， 那么向父节点凡湖Fail
/// 选择节点 用来在可能的行为集合中选择第一个成功的。 比如一个试图躲避枪击的AI角色， 它可以通过寻找隐蔽点， 或离开危险区域， 或寻找援助等多种方式实现目标。
/// 利用选择节点，他会尝试寻找Cover，失败后在试图逃离危险区域。
/// </summary>
public class Selector : Branch
{
public Selector(bool shuffle)
{
if (shuffle)
{
var n = children.Count;
while (n > 1)
{
n--;
var k = Mathf.FloorToInt(Random.value * (n + 1));
var value = children[k];
children[k] = children[n];
children[n] = value;
}
}
}
public override BTState Tick()
{
var childState = children[activeChild].Tick();
switch (childState)
{
case BTState.Success:
activeChild = 0;
return BTState.Success;
case BTState.Failure:
activeChild++;
if (activeChild == children.Count)
{
activeChild = 0;
return BTState.Failure;
}
else
return BTState.Continue;
case BTState.Continue:
return BTState.Continue;
case BTState.Abort:
activeChild = 0;
return BTState.Abort;
}
throw new System.Exception("This should never happen, but clearly it has.");
}
}
/// <summary>
/// 行为节点 调用方法，或运行协程。完成实际工作， 例如播放动画，让角色移动位置，感知敌人，更换武器，播放声音，增加生命值等。
/// </summary>
public class Action : BTNode
{
System.Action fn;
System.Func<IEnumerator<BTState>> coroutineFactory;
IEnumerator<BTState> coroutine;
public Action(System.Action fn)
{
this.fn = fn;
}
public Action(System.Func<IEnumerator<BTState>> coroutineFactory)
{
this.coroutineFactory = coroutineFactory;
}
public override BTState Tick()
{
if (fn != null)
{
fn();
return BTState.Success;
}
else
{
if (coroutine == null)
coroutine = coroutineFactory();
if (!coroutine.MoveNext())
{
coroutine = null;
return BTState.Success;
}
var result = coroutine.Current;
if (result == BTState.Continue)
return BTState.Continue;
else
{
coroutine = null;
return result;
}
}
}
public override string ToString()
{
return "Action : " + fn.Method.ToString();
}
}
/// <summary>
/// 条件节点 调用方法，如果方法返回true则返回成功，否则返回失败。
/// 用来测试当前是否满足某些性质或条件，例如“玩家是否在20米之内？”“是否能看到玩家？”“生命值是否大于50？”“弹药是否足够？”等
/// </summary>
public class Condition : BTNode
{
public System.Func<bool> fn;
public Condition(System.Func<bool> fn)
{
this.fn = fn;
}
public override BTState Tick()
{
return fn() ? BTState.Success : BTState.Failure;
}
public override string ToString()
{
return "Condition : " + fn.Method.ToString();
}
}
/// <summary>
/// 当方法为True的时候 尝试执行当前 子节点
/// </summary>
public class ConditionalBranch : Block
{
public System.Func<bool> fn;
bool tested = false;
public ConditionalBranch(System.Func<bool> fn)
{
this.fn = fn;
}
public override BTState Tick()
{
if (!tested)
{
tested = fn();
}
if (tested)
{
// 当前子节点执行完就进入下一个节点(超上限就返回到第一个)
var result = base.Tick();
// 没执行完
if (result == BTState.Continue)
return BTState.Continue;
else
{
tested = false;
// 最后一个子节点执行完，才会为Ture
return result;
}
}
else
{
return BTState.Failure;
}
}
public override string ToString()
{
return "ConditionalBranch : " + fn.Method.ToString();
}
}
/// <summary>
/// While节点 只要方法 返回True 就执行所有子节点， 否则返回 Failure
/// </summary>
public class While : Block
{
public System.Func<bool> fn;
public While(System.Func<bool> fn)
{
this.fn = fn;
}
public override BTState Tick()
{
if (fn())
base.Tick();
else
{
//if we exit the loop
ResetChildren();
return BTState.Failure;
}
return BTState.Continue;
}
public override string ToString()
{
return "While : " + fn.Method.ToString();
}
}
/// <summary>
/// 阻塞节点 如果当前子节点是Continue 说明没有执行完，阻塞着，执行完之后在继续它后面的兄弟节点 不管成功失败。
/// 如果当前结点是最后一个节点并执行完毕，说明成功！否则就是处于Continue状态。
/// 几个基本上是抽象节点， 像是让所有子节点都执行一遍， 当前子节点执行完就进入下一个节点(超上限就返回到第一个)
/// </summary>
public abstract class Block : Branch
{
public override BTState Tick()
{
switch (children[activeChild].Tick())
{
case BTState.Continue:
return BTState.Continue;
default:
activeChild++;
if (activeChild == children.Count)
{
activeChild = 0;
return BTState.Success;
}
return BTState.Continue;
}
}
}
public class Root : Block
{
public bool isTerminated = false;
public override BTState Tick()
{
if (isTerminated) return BTState.Abort;
while (true)
{
switch (children[activeChild].Tick())
{
case BTState.Continue:
return BTState.Continue;
case BTState.Abort:
isTerminated = true;
return BTState.Abort;
default:
activeChild++;
if (activeChild == children.Count)
{
activeChild = 0;
return BTState.Success;
}
continue;
}
}
}
}
/// <summary>
/// 多次运行子节点（一个子节点执行一次就算一次）
/// </summary>
public class Repeat : Block
{
public int count = 1;
int currentCount = 0;
public Repeat(int count)
{
this.count = count;
}
public override BTState Tick()
{
if (count > 0 && currentCount < count)
{
var result = base.Tick();
switch (result)
{
case BTState.Continue:
return BTState.Continue;
default:
currentCount++;
if (currentCount == count)
{
currentCount = 0;
return BTState.Success;
}
return BTState.Continue;
}
}
return BTState.Success;
}
public override string ToString()
{
return "Repeat Until : " + currentCount + " / " + count;
}
}
/// <summary>
/// 随机的顺序 执行子节点
/// </summary>
public class RandomSequence : Block
{
int[] m_Weight = null;
int[] m_AddedWeight = null;
/// <summary>
/// 每次再次触发时，将选择一个随机子节点
/// </summary>
/// <param name="weight">保留null，以便所有子节点具有相同的权重。
/// 如果权重低于子节点， 则后续子节点的权重都为1</param>
public RandomSequence(int[] weight = null)
{
activeChild = -1;
m_Weight = weight;
}
public override Branch OpenBranch(params BTNode[] children)
{
m_AddedWeight = new int[children.Length];
for (int i = 0; i < children.Length; ++i)
{
int weight = 0;
int previousWeight = 0;
if (m_Weight == null || m_Weight.Length <= i)
{//如果没有那个权重， 就将权重 设置为1
weight = 1;
}
else
weight = m_Weight[i];
if (i > 0)
previousWeight = m_AddedWeight[i - 1];
m_AddedWeight[i] = weight + previousWeight;
}
return base.OpenBranch(children);
}
public override BTState Tick()
{
if (activeChild == -1)
PickNewChild();
var result = children[activeChild].Tick();
switch (result)
{
case BTState.Continue:
return BTState.Continue;
default:
PickNewChild();
return result;
}
}
void PickNewChild()
{
int choice = Random.Range(0, m_AddedWeight[m_AddedWeight.Length - 1]);
for (int i = 0; i < m_AddedWeight.Length; ++i)
{
if (choice - m_AddedWeight[i] <= 0)
{
activeChild = i;
break;
}
}
}
public override string ToString()
{
return "Random Sequence : " + activeChild + "/" + children.Count;
}
}
/// <summary>
/// 暂停执行几秒钟。
/// </summary>
public class Wait : BTNode
{
public float seconds = 0;
float future = -1;
public Wait(float seconds)
{
this.seconds = seconds;
}
public override BTState Tick()
{
if (future < 0)
future = Time.time + seconds;
if (Time.time >= future)
{
future = -1;
return BTState.Success;
}
else
return BTState.Continue;
}
public override string ToString()
{
return "Wait : " + (future - Time.time) + " / " + seconds;
}
}
/// <summary>
/// 设置动画 trigger 参数
/// </summary>
public class Trigger : BTNode
{
Animator animator;
int id;
string triggerName;
bool set = true;
//如果 set == false, 则重置trigger而不是设置它。
public Trigger(Animator animator, string name, bool set = true)
{
this.id = Animator.StringToHash(name);
this.animator = animator;
this.triggerName = name;
this.set = set;
}
public override BTState Tick()
{
if (set)
animator.SetTrigger(id);
else
animator.ResetTrigger(id);
return BTState.Success;
}
public override string ToString()
{
return "Trigger : " + triggerName;
}
}
/// <summary>
/// 设置动画 boolean 参数
/// </summary>
public class SetBool : BTNode
{
Animator animator;
int id;
bool value;
string triggerName;
public SetBool(Animator animator, string name, bool value)
{
this.id = Animator.StringToHash(name);
this.animator = animator;
this.value = value;
this.triggerName = name;
}
public override BTState Tick()
{
animator.SetBool(id, value);
return BTState.Success;
}
public override string ToString()
{
return "SetBool : " + triggerName + " = " + value.ToString();
}
}
/// <summary>
/// 等待animator达到一个状态。
/// </summary>
public class WaitForAnimatorState : BTNode
{
Animator animator;
int id;
int layer;
string stateName;
public WaitForAnimatorState(Animator animator, string name, int layer = 0)
{
this.id = Animator.StringToHash(name);
if (!animator.HasState(layer, this.id))
{
Debug.LogError("The animator does not have state: " + name);
}
this.animator = animator;
this.layer = layer;
this.stateName = name;
}
public override BTState Tick()
{
var state = animator.GetCurrentAnimatorStateInfo(layer);
if (state.fullPathHash == this.id || state.shortNameHash == this.id)
return BTState.Success;
return BTState.Continue;
}
public override string ToString()
{
return "Wait For State : " + stateName;
}
}
/// <summary>
/// 设置 GameObject 的激活状态
/// </summary>
public class SetActive : BTNode
{
GameObject gameObject;
bool active;
public SetActive(GameObject gameObject, bool active)
{
this.gameObject = gameObject;
this.active = active;
}
public override BTState Tick()
{
gameObject.SetActive(this.active);
return BTState.Success;
}
public override string ToString()
{
return "Set Active : " + gameObject.name + " = " + active;
}
}
/// <summary>
/// 等待animator从SendSignal状态机行为 接收信号。 SendSignal : StateMachineBehaviour
/// </summary>
public class WaitForAnimatorSignal : BTNode
{
// 进入或退出动画都为 False， 只有执行中为True
internal bool isSet = false;
string name;
int id;
public WaitForAnimatorSignal(Animator animator, string name, string state, int layer = 0)
{
this.name = name;
this.id = Animator.StringToHash(name);
if (!animator.HasState(layer, this.id))
{
Debug.LogError("The animator does not have state: " + name);
}
else
{
SendSignal.Register(animator, name, this);
}
}
public override BTState Tick()
{
if (!isSet)
return BTState.Continue;
else
{
isSet = false;
return BTState.Success;
}
}
public override string ToString()
{
return "Wait For Animator Signal : " + name;
}
}
/// <summary>
/// 终止节点 切换到中止 状态
/// </summary>
public class Terminate : BTNode
{
public override BTState Tick()
{
return BTState.Abort;
}
}
/// <summary>
/// Log 输出Log 的节点
/// </summary>
public class Log : BTNode
{
string msg;
public Log(string msg)
{
this.msg = msg;
}
public override BTState Tick()
{
Debug.Log(msg);
return BTState.Success;
}
}
}
#if UNITY_EDITOR
namespace BTAI
{
public interface IBTDebugable
{
Root GetAIRoot();
}
}
#endifusing BTAI;
using System.Collections.Generic;
using UnityEditor;
using UnityEngine;
namespace Gamekit2D
{
/// <summary>
/// 运行是查看 行为树中所有节点的状态
/// </summary>
public class BTDebug : EditorWindow
{
protected BTAI.Root _currentRoot = null;
[MenuItem("Kit Tools/Behaviour Tree Debug")]
static void OpenWindow()
{
BTDebug btdebug = GetWindow<BTDebug>();
btdebug.Show();
}
private void OnGUI()
{
if (!Application.isPlaying)
{
EditorGUILayout.HelpBox("Only work during play mode.", MessageType.Info);
}
else
{
if (_currentRoot == null)
FindRoot();
else
{
RecursiveTreeParsing(_currentRoot, 0, true);
}
}
}
void Update()
{
Repaint();
}
void RecursiveTreeParsing(Branch branch, int indent, bool parentIsActive)
{
List<BTNode> nodes = branch.Children();
for (int i = 0; i < nodes.Count; ++i)
{
EditorGUI.indentLevel = indent;
bool isActiveChild = branch.ActiveChild() == i;
GUI.color = (isActiveChild && parentIsActive) ? Color.green : Color.white;
EditorGUILayout.LabelField(nodes[i].ToString());
if (nodes[i] is Branch)
RecursiveTreeParsing(nodes[i] as Branch, indent + 1, isActiveChild);
}
}
void FindRoot()
{
if (Selection.activeGameObject == null)
{
_currentRoot = null;
return;
}
IBTDebugable debugable = Selection.activeGameObject.GetComponentInChildren<IBTDebugable>();
if (debugable != null)
{
_currentRoot = debugable.GetAIRoot();
}
}
}
}You can view the behavior tree where the TestBT.cs object is located in the menu "Kit Tools/Behaviour Tree Debug"
![C#/implementation steps based on Unity behavior tree [Pure code]](https://img.php.cn//upload/image/205/172/647/1532573154636123.png "1532573154636123.png")
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