Unity3d之Navigation导航系统（AII敌人）

Navigation：是通过 enum 和  switch 来进行状态机的转换从而实现AI巡逻和攻击以及追踪

    private GameObject playerUnit;          //获取玩家单位
    private Animator thisAnimator;          //自身动画组件
    private Vector3 initialPosition;            //初始位置

    public float wanderRadius;          //游走半径，移动状态下，如果超出游走半径会返回出生位置
    public float alertRadius;         //警戒半径，玩家进入后怪物会发出警告，并一直面朝玩家
    public float defendRadius;          //自卫半径，玩家进入后怪物会追击玩家，当距离<攻击距离则会发动攻击（或者触发战斗）
    public float chaseRadius;            //追击半径，当怪物超出追击半径后会放弃追击，返回追击起始位置

    public float attackRange;            //攻击距离
    public float walkSpeed;          //移动速度
    public float runSpeed;          //跑动速度
    public float turnSpeed;         //转身速度，建议0.1

    private enum MonsterState
    {
        STAND,      //原地呼吸
        CHECK,       //原地观察
        WALK,       //移动
        WARN,       //盯着玩家
        CHASE,      //追击玩家
        RETURN      //超出追击范围后返回
    }
    private MonsterState currentState = MonsterState.STAND;          //默认状态为原地呼吸

    public float[] actionWeight = { 3000, 3000, 4000 };         //设置待机时各种动作的权重，顺序依次为呼吸、观察、移动
    public float actRestTme;            //更换待机指令的间隔时间
    private float lastActTime;          //最近一次指令时间

    private float diatanceToPlayer;         //怪物与玩家的距离
    private float diatanceToInitial;         //怪物与初始位置的距离
    private Quaternion targetRotation;         //怪物的目标朝向

    private bool is_Warned = false;
    private bool is_Running = false;

    void Start()
    {
        playerUnit = GameObject.FindGameObjectWithTag("Player");
        thisAnimator = GetComponent<Animator>();

        //保存初始位置信息
        initialPosition = gameObject.GetComponent<Transform>().position;

        //检查并修正怪物设置
        //1. 自卫半径不大于警戒半径，否则就无法触发警戒状态，直接开始追击了
        defendRadius = Mathf.Min(alertRadius, defendRadius);
        //2. 攻击距离不大于自卫半径，否则就无法触发追击状态，直接开始战斗了
        attackRange = Mathf.Min(defendRadius, attackRange);
        //3. 游走半径不大于追击半径，否则怪物可能刚刚开始追击就返回出生点
        wanderRadius = Mathf.Min(chaseRadius, wanderRadius);

        //随机一个待机动作
        RandomAction();
    }

    /// <summary>
    /// 根据权重随机待机指令
    /// </summary>
    void RandomAction()
    {
        //更新行动时间
        lastActTime = Time.time;
        //根据权重随机
        float number = Random.Range(0, actionWeight[0] + actionWeight[1] + actionWeight[2]);
        if (number <= actionWeight[0])
        {
            currentState = MonsterState.STAND;
            thisAnimator.SetTrigger("Stand");
        }
        else if (actionWeight[0] < number && number <= actionWeight[0] + actionWeight[1])
        {
            currentState = MonsterState.CHECK;
            thisAnimator.SetTrigger("Check");
        }
        if (actionWeight[0] + actionWeight[1] < number && number <= actionWeight[0] + actionWeight[1] + actionWeight[2])
        {
            currentState = MonsterState.WALK;
            //随机一个朝向
            targetRotation = Quaternion.Euler(0, Random.Range(1, 5) * 90, 0);
            thisAnimator.SetTrigger("Walk");
        }
    }

    void Update()
    {
        switch (currentState)
        {
            //待机状态，等待actRestTme后重新随机指令
            case MonsterState.STAND:
                if (Time.time - lastActTime > actRestTme)
                {
                    RandomAction();         //随机切换指令
                }
                //该状态下的检测指令
                EnemyDistanceCheck();
                break;

            //待机状态，由于观察动画时间较长，并希望动画完整播放，故等待时间是根据一个完整动画的播放长度，而不是指令间隔时间
            case MonsterState.CHECK:
                if (Time.time - lastActTime > thisAnimator.GetCurrentAnimatorStateInfo(0).length)
                {
                    RandomAction();         //随机切换指令
                }
                //该状态下的检测指令
                EnemyDistanceCheck();
                break;

            //游走，根据状态随机时生成的目标位置修改朝向，并向前移动
            case MonsterState.WALK:
                transform.Translate(Vector3.forward * Time.deltaTime * walkSpeed);
                transform.rotation = Quaternion.Slerp(transform.rotation, targetRotation, turnSpeed);

                if (Time.time - lastActTime > actRestTme)
                {
                    RandomAction();         //随机切换指令
                }
                //该状态下的检测指令
                WanderRadiusCheck();
                break;

            //警戒状态，播放一次警告动画和声音，并持续朝向玩家位置
            case MonsterState.WARN:
                if (!is_Warned)
                {
                    thisAnimator.SetTrigger("Warn");
                    gameObject.GetComponent<AudioSource>().Play();
                    is_Warned = true;
                }
                //持续朝向玩家位置
                targetRotation = Quaternion.LookRotation(playerUnit.transform.position - transform.position, Vector3.up);
                transform.rotation = Quaternion.Slerp(transform.rotation, targetRotation, turnSpeed);
                //该状态下的检测指令
                WarningCheck();
                break;

            //追击状态，朝着玩家跑去
            case MonsterState.CHASE:
                if (!is_Running)
                {
                    thisAnimator.SetTrigger("Run");
                    is_Running = true;
                }
                transform.Translate(Vector3.forward * Time.deltaTime * runSpeed);
                //朝向玩家位置
                targetRotation = Quaternion.LookRotation(playerUnit.transform.position - transform.position, Vector3.up);
                transform.rotation = Quaternion.Slerp(transform.rotation, targetRotation, turnSpeed);
                //该状态下的检测指令
                ChaseRadiusCheck();
                break;

            //返回状态，超出追击范围后返回出生位置
            case MonsterState.RETURN:
                //朝向初始位置移动
                targetRotation = Quaternion.LookRotation(initialPosition - transform.position, Vector3.up);
                transform.rotation = Quaternion.Slerp(transform.rotation, targetRotation, turnSpeed);
                transform.Translate(Vector3.forward * Time.deltaTime * runSpeed);
                //该状态下的检测指令
                ReturnCheck();
                break;
        }
    }

    /// <summary>
    /// 原地呼吸、观察状态的检测
    /// </summary>
    void EnemyDistanceCheck()
    {
        diatanceToPlayer = Vector3.Distance(playerUnit.transform.position, transform.position);
        if (diatanceToPlayer < attackRange)
        {
            SceneManager.LoadScene("Battle");
        }
        else if (diatanceToPlayer < defendRadius)
        {
            currentState = MonsterState.CHASE;
        }
        else if (diatanceToPlayer < alertRadius)
        {
            currentState = MonsterState.WARN;
        }
    }

    /// <summary>
    /// 警告状态下的检测，用于启动追击及取消警戒状态
    /// </summary>
    void WarningCheck()
    {
        diatanceToPlayer = Vector3.Distance(playerUnit.transform.position, transform.position);
        if (diatanceToPlayer < defendRadius)
        {
            is_Warned = false;
            currentState = MonsterState.CHASE;
        }

        if (diatanceToPlayer > alertRadius)
        {
            is_Warned = false;
            RandomAction();
        }
    }

    /// <summary>
    /// 游走状态检测，检测敌人距离及游走是否越界
    /// </summary>
    void WanderRadiusCheck()
    {
        diatanceToPlayer = Vector3.Distance(playerUnit.transform.position, transform.position);
        diatanceToInitial = Vector3.Distance(transform.position, initialPosition);

        if (diatanceToPlayer < attackRange)
        {
            SceneManager.LoadScene("Battle");
        }
        else if (diatanceToPlayer < defendRadius)
        {
            currentState = MonsterState.CHASE;
        }
        else if (diatanceToPlayer < alertRadius)
        {
            currentState = MonsterState.WARN;
        }

        if (diatanceToInitial > wanderRadius)
        {
            //朝向调整为初始方向
            targetRotation = Quaternion.LookRotation(initialPosition - transform.position, Vector3.up);
        }
    }

    /// <summary>
    /// 追击状态检测，检测敌人是否进入攻击范围以及是否离开警戒范围
    /// </summary>
    void ChaseRadiusCheck()
    {
        diatanceToPlayer = Vector3.Distance(playerUnit.transform.position, transform.position);
        diatanceToInitial = Vector3.Distance(transform.position, initialPosition);

        if (diatanceToPlayer < attackRange)
        {
            SceneManager.LoadScene("Battle");
        }
        //如果超出追击范围或者敌人的距离超出警戒距离就返回
        if (diatanceToInitial > chaseRadius || diatanceToPlayer > alertRadius)
        {
            currentState = MonsterState.RETURN;
        }
    }

    /// <summary>
    /// 超出追击半径，返回状态的检测，不再检测敌人距离
    /// </summary>
    void ReturnCheck()
    {
        diatanceToInitial = Vector3.Distance(transform.position, initialPosition);
        //如果已经接近初始位置，则随机一个待机状态
        if (diatanceToInitial < 0.5f)
        {
            is_Running = false;
            RandomAction();
        }
    }