AI-有限状态机（追击，巡逻）

最新推荐文章于 2025-05-17 20:15:46 发布

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本文详细介绍了一种游戏AI设计模式——有限状态机（FSM）的实现过程。通过定义状态、过渡条件和行为，实现了敌人AI从巡逻到追逐玩家的状态转换。代码示例展示了如何在Unity中使用C#构建FSM，包括状态枚举、状态类和状态系统。

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有限状态机的基类，包含各种状态

using System.Collections;
using System.Collections.Generic;
using UnityEngine;


public enum Transition
{
    NullTransition=0,
    SeePlayer,
    LostPlayer
}


public enum StateID
{
    NullStateID=0,
    Patrol,
    Chase
}

public abstract class FSMState
{
    protected StateID stateID;
    public StateID ID { get { return stateID; } }
    protected Dictionary<Transition, StateID> map = new Dictionary<Transition, StateID>();
    protected FSMSystem fsm;

    public FSMState(FSMSystem fsm)
    {
        this.fsm = fsm;
    }

    public void AddTransition(Transition transition,StateID id)
    {
        if (transition==Transition.NullTransition)
        {
            Debug.LogError("不允许NullTransition");return;
        }
        if (id==StateID.NullStateID)
        {
            Debug.LogError("不允许NullStateID");return;
        }
        if (map.ContainsKey(transition))                // 判断key是否存在
        {
            Debug.LogError("添加转换条件的时候" + transition + "已经存在于map中");return;
        }
        map.Add(transition, id);
    }

    public void DeleteTransition(Transition transition)
    {
        if (transition == Transition.NullTransition)
        {
            Debug.LogError("不允许NullTransition"); return;
        }
        if (map.ContainsKey(transition)==false)                // 判断key是否存在
        {
            Debug.LogError("删除转换条件的时候" + transition + "不存在于map中"); return;
        }
        map.Remove(transition);
    }

    public StateID GetOutputState (Transition transition)
    {
        if (map.ContainsKey(transition))
        {
            return map[transition];
        }
        return StateID.NullStateID;
    }

    //进入状态之前的虚函数
    public virtual void DoBeforEntering() { }
    //离开状态，状态发生转换
    public virtual void DoAfterLeaving() { }
    //抽象方法必须重写
    public abstract void Act(GameObject gameObject);
    //判断转换条件
    public abstract void Reason(GameObject gameObject);
}

控制状态之间的转换

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class FSMSystem
{
    private Dictionary<StateID, FSMState> states=new Dictionary<StateID, FSMState>();

    private StateID currentStateID;
    private FSMState currentState;

    public void AddState(FSMState s)
    {
        if (s==null)
        {
            Debug.LogError("FSMState不能为空");return;
        }
            //默认状态
        if (currentState==null)
        {
            currentState = s;
            currentStateID = s.ID;
        }
        //添加到字典里
        if (states.ContainsKey(s.ID))
        {
            Debug.LogError("状态" + s.ID + "已经存在");return;
        }
        states.Add(s.ID, s);
    }

    public void DeleteState(StateID id)
    {
        if (id==StateID.NullStateID)
        {
            Debug.LogError("无法删除空状态");return;
        }
        if (states.ContainsKey(id)==false)
        {
            Debug.LogError("无法删除不存在的：" + id);return;
        }
        states.Remove(id);
    }

    //根据条件进行状态切换
    public void PerformTransition(Transition transition)
    {
        if (transition ==Transition.NullTransition)
        {
            Debug.LogError("无法执行空的转换条件");return;
        }
        StateID id = currentState.GetOutputState(transition);

        if (id==StateID.NullStateID)
        {
            Debug.LogWarning("当前状态" + currentStateID + "无法根据转换条件" + transition + "发生转换");return;
        }
        FSMState fSMState = states[id];

        currentState.DoAfterLeaving();          //旧状态离开
        currentState = fSMState;
        currentStateID = id;
        currentState.DoBeforEntering();         //新状态进入
    }

    //调用Act方法
    public void Update(GameObject gameObject)
    {
        currentState.Act(gameObject);
        currentState.Reason(gameObject);
    }

}

敌人类

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class Enemy : MonoBehaviour {

    private FSMSystem fsm;
	
	void Start () {
        InitFSM();
	}
	
	//对有限状态机进行初始化
    private void InitFSM()
    {
        fsm = new FSMSystem();
        FSMState patrolState = new PatrolState(fsm);
        //转换条件
        patrolState.AddTransition(Transition.SeePlayer,StateID.Chase);

        FSMState chaseState = new ChaseState(fsm);
        chaseState.AddTransition(Transition.LostPlayer, StateID.Patrol);

        fsm.AddState(patrolState);
        fsm.AddState(chaseState);
    }

	void Update () {
        fsm.Update(this.gameObject);
	}
}

巡逻状态和追击状态

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class PatrolState : FSMState
{
    //路径点
    private List<Transform> path = new List<Transform>();
    private int index = 0;      //移动的开始索引
    private Transform playerTransform;

    public PatrolState(FSMSystem fsm) : base(fsm)
    {
        stateID = StateID.Patrol;

        //在这里获取一次，节省性能
        Transform pathTran = GameObject.Find("Path").transform;
        Transform[] children = pathTran.GetComponentsInChildren<Transform>();   //还包含父物体
        //剔除父物体
        foreach (Transform child in children)
        {
            if (child!= pathTran)
            {
                path.Add(child);
            }
        }

        playerTransform = GameObject.Find("Player").transform;

    }

    //这个方法在FSMSystem中调用
    public override void Act(GameObject gameObject)
    {
        gameObject.transform.LookAt(path[index].position);
        gameObject.transform.Translate(Vector3.forward * Time.deltaTime * 3);
        if (Vector3.Distance(gameObject.transform.position,path[index].position)<1)     //自身位置与目标位置的距离
        {
            index++;
            index %= path.Count;    //index在数组内循环
        }
    }

    public override void Reason(GameObject gameObject)
    {
        //与主角距离小于3的时候开始追击玩家
        if (Vector3.Distance(playerTransform.position,gameObject.transform.position)<3)
        {
            fsm.PerformTransition(Transition.SeePlayer);
        } 
    }
}

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class ChaseState : FSMState
{
    private Transform playerTransform;

    public ChaseState(FSMSystem fsm) : base(fsm)
    {
        stateID = StateID.Chase;
        playerTransform = GameObject.Find("Player").transform;
    }

    public override void Act(GameObject gameObject)
    {
        gameObject.transform.LookAt(playerTransform.position);
        gameObject.transform.Translate(Vector3.forward * 2 * Time.deltaTime);
    }

    public override void Reason(GameObject gameObject)
    {
        //与主角距离大于6时,执行寻路状态
        if (Vector3.Distance(playerTransform.position, gameObject.transform.position) > 6)
        {
            fsm.PerformTransition(Transition.LostPlayer);
        }
    }
}