Unity 몬스터 AI 상태 머신 만들기 — 대기·추적·공격·복귀 설계

enum MonsterState { Idle, Moving, Following, Attacking, Returning }
MonsterState state = MonsterState.Idle;
float idleTime;

void Update()
{
    switch (state)
    {
        case MonsterState.Idle:
            idleTime += Time.deltaTime;
            if (FindEnemy()) Change(MonsterState.Following);
            else if (idleTime > 15f) Change(MonsterState.Moving);
            break;
        case MonsterState.Moving:
            if (FindEnemy()) Change(MonsterState.Following);
            else if (MoveToNextPoint()) Change(MonsterState.Idle);       // 도착
            break;
        case MonsterState.Following:
            if (Distance(target) > 10f || Distance(spawnPoint) > 10f) Change(MonsterState.Returning);
            else if (InAttackRange(target)) Change(MonsterState.Attacking);
            else Chase(target);
            break;
        case MonsterState.Attacking:
            if (target.IsDead) Change(MonsterState.Returning);
            else if (!InAttackRange(target)) Change(MonsterState.Following);
            else Attack(target);
            break;
        case MonsterState.Returning:
            if (MoveTo(spawnPoint)) Change(MonsterState.Idle);           // 도착
            break;
    }
}

void Change(MonsterState next)
{
    state = next;
    idleTime = 0f;
    invincible = next == MonsterState.Returning;                         // 돌아가는 동안 무적
    if (next == MonsterState.Returning) LookAt(spawnPoint);              // entry: 스폰 위치를 바라봄
}

RaycastHit hit;
Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
int layer_mask = LayerMask.GetMask("Terrain");
if (Physics.Raycast(ray, out hit, 1000, layer_mask))
{
    hit.point;   // 피킹된 3D 위치
}

// 플레이어 전용이던 탐색을 컨트롤러 종류로 일반화한다
public List<T> SearchEnemies<T>(float radius) where T : Controller
{
    List<T> found = new List<T>();
    foreach (T c in FindObjectsOfType<T>())
    {
        if (Vector3.Distance(c.transform.position, transform.position) <= radius)
            found.Add(c);
    }
    return found;
}

// 쓰는 쪽
var players = SearchEnemies<PlayerController>(10f);
var monsters = SearchEnemies<MonsterController>(10f);