本文是 XYGame-AI设计3-行为树-第1版本 的 AI 丰富版本，同时也是 XYGame-AI设计2-FSM 的行为树重构版本。

根据下方策划文档，得出以下行为树结构：

总结

相比版本1，本版本只是让 AI 规则更加复杂。每帧更新仍然从 root 节点开始遍历，通过不同的决策找出需要执行的叶子节点并执行 Action 行为逻辑。但现在设计的树形结构各节点之间存在依赖关系，因此虽然看起来可以简单粗暴地每次从 root 开始遍历，更好的设计是保存当前节点，下次更新直接从当前节点继续执行——这个过程类似函数调用时的地址保存与恢复。

这样做虽然能省去每次从 root 遍历的性能开销，但带来了以下几个难点：

  1. 行为节点的恢复与保存：何时开始执行行为，何时执行行为的条件等问题。
  2. 行为的条件评定：严格来看，虽然从 root 开始遍历，但得出的行为始终是在严格条件下执行的。实际的性能开销来自部分条件的重合评定，而非 root 遍历本身。
  3. 节点将携带执行状态，例如 Running、Complete、Looping 等。

策划文档

Action 与 Condition 实现代码

/*
* Author:  caoshanshan
* Email:   me@dreamyouxi.com
  Behavior Tree  's Actions
 * 行为树游戏逻辑部分
 */
using UnityEngine;
using System.Collections;

namespace BehaviorTree.Action
{
    //--------------------------------------------------游戏逻辑实际的  Action
    public class SearchNearestTarget : ActionBase
    {//寻找最近的玩家作为目标
        public override bool Visit(Entity target)
        {
            Enemy host = target as Enemy;

            if (host == null) return false;

            float minDis = float.MaxValue;
            Entity t = null;
            foreach (Entity h in HeroMgr.ins.GetHeros())
            {//找出一个最近的玩家 作为锁定目标
                if (h.IsMaxTarget())
                {
                    continue;
                }
                float dis = h.ClaculateDistance(host.x, host.y);
                if (dis < minDis)
                {
                    t = h;
                    minDis = dis;
                }
            }

            if (t != null)
            {
                host.target = t;
                host.is_hit_tower = false;
                return true;
            }

            return false;
        }
    }

    public class MoveToTarget : ActionBase
    {
        public override bool Visit(Entity target)
        {
            Enemy host = target as Enemy;
            if (host == null) return false;
            host.dir = (int)Utils.GetAngle(host.pos, host.target.pos);//委托给Run状态去做
            return true;
        }
    }
    public class AttackTarget : ActionBase
    {
        public override bool Visit(Entity target)
        {
            Enemy host = target as Enemy;
            if (host == null) return false;
            if (host.target.IsHero && host.IsHeroRandomAtk(0.03f))
            {
                // 随机化攻击  减弱攻击强度
                target.atk = true;
                return true;
            }
            return false;
        }
    }

    public class SearchNearestTower : ActionBase
    {//仇恨指向最近的塔
        public override bool Visit(Entity target)
        {
            Enemy host = target as Enemy;

            if (host == null) return false;

            float minDis = float.MaxValue;
            Entity t = null;
            foreach (Entity h in BuildingMgr.ins.GetBuildings())
            {//找出一个最近的玩家 作为锁定目标
                if (h.IsMaxTarget())
                {
                    continue;
                }
                float dis = h.ClaculateDistance(host.x, host.y);
                if (dis < minDis)
                {
                    t = h;
                    minDis = dis;
                }
            }

            if (t != null)
            {
                host.target = t;
                host.is_hit_tower = false;
                // Debug.LogError("目标指向最近的塔");
                return true;
            }

            return false;
        }
    }
    public class SearchNearestHero : ActionBase
    {//寻找最近的玩家作为目标
        public override bool Visit(Entity target)
        {
            Enemy host = target as Enemy;

            if (host == null) return false;

            float minDis = float.MaxValue;
            Entity t = null;
            foreach (Entity h in HeroMgr.ins.GetHeros())
            {//找出一个最近的玩家 作为锁定目标
                if (h.IsMaxTarget())
                {
                    continue;
                }
                float dis = h.ClaculateDistance(host.x, host.y);
                if (dis < minDis)
                {
                    t = h;
                    minDis = dis;
                }
            }

            if (t != null)
            {
                host.target = t;
                host.is_hit_tower = false;
                //  Debug.LogError("目标指向最近的玩家");
                return true;
            }

            return false;
        }
    }

    public class SetTarget : ActionBase
    {
        public override bool Visit(Entity target)
        {
            Enemy host = target as Enemy;
            var obj = host.GetTagPairOnce("BT_HitHero");
            if (obj == null)
            {
                host.target = null;
                return false;
            }
            host.target = obj.value as Entity;
            //   Debug.LogError("重新设置目标BT_HitHero");
            return true;
        }
    }
    public class NotHitTower : ConditionBase
    {//重置没有攻击塔
        public override bool Visit(Entity target)
        {
            Enemy host = target as Enemy;
            if (host == null) return false;
            host.is_hit_tower = false;
            return true;
        }
    }
    public class MoveRandom : ActionBase
    {
        int dir = 0;
        public override bool Visit(Entity target)
        {
            Enemy host = target as Enemy;
            if (host == null) return false;
            if (host.target == null) return false;
            if (host.target.isDie) return false;


            if (Utils.random_frameMS.Next(0, 300) == 5)
            { // 地图范围内的随机目标点
                Terrain terrain = AppMgr.GetCurrentApp<BattleApp>().GetCurrentWorldMap().GetTerrain();
                Vector2 to = new Vector2(Utils.random_frameMS.Next((int)(terrain.limit_x_left * 1000), (int)(terrain.limit_x_right * 1000)) / 1000f, Utils.random_frameMS.Next((int)(terrain.limit_z_down * 1000), (int)(terrain.limit_z_up * 1000)) / 1000f);
                this.dir = (int)Utils.GetAngle(host.pos, to);
            }
            host.dir = this.dir;
            return true;
        }
    }

    public class MoveRandomInAtkRange : ActionBase
    {
        int dir = 0;
        public override bool Visit(Entity target)
        {
            Enemy host = target as Enemy;
            if (host == null) return false;
            if (host.target == null) return false;
            if (host.target.isDie) return false;

            if (Utils.random_frameMS.Next(1, 200) == 2 || Mathf.Abs(host.atk_range - host.target.ClaculateDistance(host)) < 0.2f)
            {//一定概率 随机方向
                dir = (int)Utils.GetAngle(host.pos, host.target.pos);
                //  Debug.LogError("随机攻击范围内运动 " + dir);
            }
            host.dir = this.dir;
            return true;
        }
    }
}

/*
* Author:  caoshanshan
* Email:   me@dreamyouxi.com
  Behavior Tree  's Conditions
 * 行为树游戏逻辑部分
 */
using UnityEngine;
using System.Collections;

namespace BehaviorTree.Condition
{
    //--------------------------------------------------游戏逻辑实际的 Condition
    public class TargetHasNotInAtkRange : ConditionBase
    {//目标不在否在攻击范围内
        public override bool Visit(Entity target)
        {
            Enemy host = target as Enemy;
            if (host == null) return false;
            if (host.target == null) return false;
            if (host.atk_range > host.target.ClaculateDistance(host))
            {//范围内
                return false;
            }
            return true;
        }
    }
    public class IsCDMax : ConditionBase
    {//CD是否结束
        public override bool Visit(Entity target)
        {
            Enemy host = target as Enemy;
            if (host == null) return false;
            if (host.target == null) return false;
            if (host.cd.IsMax())
            {
                host.cd.Reset();
                return true;
            }
            return false;
        }
    }
    public class NotTargetOrDie : ConditionBase
    {//没有目标或者死亡
        public override bool Visit(Entity target)
        {
            Enemy host = target as Enemy;
            if (host == null) return true;
            if (host.target == null) return true;
            if (host.target.isDie) return true;
            return false;
        }
    }

    public class HasTower : ConditionBase
    {//存在塔
        public override bool Visit(Entity target)
        {
            if (BuildingMgr.ins.GetBuildings().Count > 0)
            {
             //   Debug.LogError("存在塔");
                return true;
            }
            return false;
        }
    }

    public class HasHitTower : ConditionBase
    {//攻击了塔
        public override bool Visit(Entity target)
        {
            Enemy host = target as Enemy;
            if (host == null) return true;
            return host.is_hit_tower;
        }
    }
    public class HasNotHitTower : ConditionBase
    {//没有攻击塔
        public override bool Visit(Entity target)
        {
            Enemy host = target as Enemy;
            if (host == null) return true;
            return !host.is_hit_tower;
        }
    }

    public class HasHitByHero : ConditionBase
    {//被玩家攻击
        bool ret = false;
        Entity hit_target = null;//被攻击的目标
        public override bool Visit(Entity target)
        {
            _host = target;
            if (ret)
            {
            //    Debug.LogError("被玩家攻击");
                ret = false;
                return true;
            }
            return false;
        }
        public override void OnEvent(int type, object userData)
        {
            if (this.IsInValid()) return;
            if (type == Events.ID_BATTLE_ENTITY_BEFORE_TAKEATTACKED)
            {
                AttackInfo info = userData as AttackInfo;
                Enemy host = _host as Enemy;
                if (host == null) return;
                if (info.target as Enemy != host) return;
                //自己被命中
                if (info.ownner.IsMaxTarget() == false)
                {
                   // host.target = info.ownner;
                    ret = true;
                    host.SetTag("BT_HitHero", info.ownner); // 信息 写入黑板
                }
            }
        }
        public override void OnEnter()
        {
            EventDispatcher.ins.AddEventListener(this, Events.ID_BATTLE_ENTITY_BEFORE_TAKEATTACKED);
        }
        public override void OnExit()
        {
            EventDispatcher.ins.RemoveEventListener(this, Events.ID_BATTLE_ENTITY_BEFORE_TAKEATTACKED);
        }
    }

    public class TargetIsHero : ConditionBase
    {//目标是玩家
        public override bool Visit(Entity target)
        {
            Enemy host = target as Enemy;
            if (host == null) return false;
            if (host.target == null) return false;
            if (host.target.isDie) return false;

            return host.target.IsHero;
        }
    }
    public class TargetIsTower : ConditionBase
    {//目标是塔
        public override bool Visit(Entity target)
        {
            Enemy host = target as Enemy;
            if (host == null) return false;
            if (host.target == null) return false;
            if (host.target.isDie) return false;
            if (host.target.IsTower)
            {
                //  Debug.LogError("目标是塔");
                return true;
            }
            return false;
        }
    }
    public class HasHeroInTargetRange : ConditionBase
    {//目标不在否在攻击范围内
        public override bool Visit(Entity target)
        {
            Enemy host = target as Enemy;
            if (host == null) return false;
            if (host.target == null) return false;
            foreach (Entity h in HeroMgr.ins.GetHeros())
            {
                if (host.target_distance > host.ClaculateDistance(h.x, 0, h.z))
                {//范围内
                    return true;
                }
            }
            return false;
        }
    }
    public class HasNotTarget : ConditionBase
    {//没有目标
        public override bool Visit(Entity target)
        {
            Enemy host = target as Enemy;
            if (host == null) return true;
            if (host.target == null) return true;
            return false;
        }
    }




}