浅谈游戏AI设计--有限状态机

游戏AI设计中，常用的方法有有限状态机，行为树等，最基本的也就是状态机了，下面用一个实例来记录下有限状态机的实现。

1，设计有限状态机

首先需要为游戏AI设计出合理的状态图，并且确定各个状态的转换条件。下面设计一个简单的有限状态机。

状态：

• 巡逻
• 攻击
• 躲避

状态转换条件

• 敌人距离AI的距离

• 血量

  
  图片.png

2，代码实现

设计模式--状态模式

状态模式.png
context类，状态机的一些初始化，以及切换状态

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using UnityEngine;

namespace Assets
{
    class Context
    {
        public Data data;
        public Ai ai;

        /// <summary>
        /// 当前状态
        /// </summary>
        Status status;

        /// <summary>
        /// 构造，默认巡逻状态
        /// </summary>
        public Context(Ai _ai)
        {
            ai = _ai;
            status = new FindStatus();
        }
        /// <summary>
        /// 改变状态   
        /// </summary>
        /// <param name="_status"></param>
        public void ChangeStatus(Status _status)
        {
            Debug.Log("血量：" + data.Hp + "距离player：" + data.DistanceAiToPlayer);
            status = _status;
        }

        /// <summary>
        /// 执行动作
        /// </summary>
        public void DoAction(Data _data)
        {
            data = _data;
            status.Action(this);
        }
        
    }
}

---

Status状态接口

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Assets
{
    interface Status
    {
        void Action(Context context);
    }
}

---

FindSatus具体状态，巡逻状态

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using UnityEngine;

namespace Assets
{
    class FindStatus : Status
    {
        public FindStatus()
        {
            Debug.Log("进入巡逻模式");

        }
        public const float MaxDistance = 5;
        public const float MaxRange = 5;
        public void Action(Context context)
        {
            context.ai.RecoveryHp();
            if(context.data.DistanceAiToPlayer < MaxDistance)
            {
                context.ChangeStatus(new AttackStatus());
            }
            else
            {
                context.ai.StopMove();
            }
        }
    }
}

---

AvoidStatus具体状态，躲避状态

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using UnityEngine;

namespace Assets
{
    class AvoidStatus : Status
    {
        public AvoidStatus()
        {
            Debug.Log("进入躲避模式");

        }
        public const float MinHp = 10;
        public void Action(Context context)
        {
           
            context.ai.FarAwayPlayer();
            if(context.data.DistanceAiToPlayer > FindStatus.MaxDistance)
            {
                context.ChangeStatus(new FindStatus());
            }
        }
    }
}

---

AttackStatus具体状态，攻击状态

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using UnityEngine;

namespace Assets
{
    class AttackStatus : Status
    {
        public AttackStatus()
        {
            Debug.Log("进入攻击模式");
        }
        public void Action(Context context)
        {
            context.ai.MoveToPlayer();
            context.ai.BeAttack();
            if(context.data.Hp < AvoidStatus.MinHp)
            {
                context.ChangeStatus(new AvoidStatus());
            }else if(context.data.Hp > AvoidStatus.MinHp && context.data.DistanceAiToPlayer > FindStatus.MaxDistance)
            {
                context.ChangeStatus(new FindStatus());
            }
        }
    }
}

---

player控制脚本

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

public class player : MonoBehaviour {
    Rigidbody rigidbody;

    // Use this for initialization
    void Start () {
        rigidbody = GetComponent<Rigidbody>();
    }
    
    // Update is called once per frame
    void Update () {
        float x = Input.GetAxis("Horizontal");
        float z = Input.GetAxis("Vertical");
        rigidbody.AddForce(new Vector3(x, 0, z).normalized * 2);
    }
}

---

游戏AI控制脚本

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

public class Ai : MonoBehaviour {

    public GameObject player;
    float Hp = 20;
    Rigidbody rigidbody;

    Context context;
    // Use this for initialization
    void Start () {
        context = new Context(this);
        rigidbody = GetComponent<Rigidbody>();
    }
    
    // Update is called once per frame
    void Update () {
        
        context.DoAction(GetData());
    }

    /// <summary>
    /// 获取各种条件
    /// </summary>
    /// <returns></returns>
    Data GetData()
    {
        Data data = new Data();
        data.DistanceAiToPlayer = Vector3.Distance(transform.position, player.transform.position);
        data.Hp = Hp;
        return data;
    }

    public void MoveToPlayer()
    {
        rigidbody.AddForce((player.transform.position - transform.position).normalized);
    }

    public void StopMove()
    {
        rigidbody.AddForce(-rigidbody.velocity);
    }

    public void BeAttack()
    {
        Hp -= 0.01f;
    }

    public void FarAwayPlayer()
    {
        rigidbody.AddForce(-(player.transform.position - transform.position).normalized*2);
    }

    public void RecoveryHp()
    {
        if(Hp < 20)
        {
            Hp += 0.1f;

        }
    }
}

---

Data条件数据

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using UnityEngine;

namespace Assets
{
    class Data
    {
        public float DistanceAiToPlayer;

        public float Hp;
        
    }
}

代码中为了便于测试，ai在攻击下会直接减Hp，每一帧减少0.01，躲避和巡逻状态会增加Hp，每一帧增加0.1。
运行结果

运行情况.png

视频转gif效果不是很好
小球是玩家控制的，大球是游戏AI

运行截图.gif