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11. 敌人AI与行为模式

EVOCOSMOS2026/4/14大约 5 分钟

敌人AI与行为模式

上一章讲了游戏 UI 界面，本章专门讲敌人怎么"思考"和行动——从简单的巡逻到复杂的追踪、攻击行为。

敌人行为的三种模式

模式比喻适用场景
固定路线巡逻保安在走廊里来回走平台跳跃、动作游戏
追踪玩家狗看到人就跟过来动作冒险、RPG
触发式行为陷阱有人靠近就激活所有类型

固定路线巡逻

敌人沿预设路径来回移动，这是最简单的敌人行为。

使用 Path2D 巡逻

C#
// 敌人沿路径巡逻
using Godot;

public partial class EnemyFollower : PathFollow2D
{
    private float _speed = 50.0f;
    private int _direction = 1; // 1=正向, -1=反向

    public override void _PhysicsProcess(double delta)
    {
        Progress += _speed * _direction * (float)delta;

        // 到达路径终点后反向
        if (ProgressRatio >= 1.0)
            _direction = -1;
        else if (ProgressRatio <= 0.0)
            _direction = 1;
    }
}

场景结构：

EnemyPath (Path2D)              ← 定义巡逻路径
└── EnemyFollower (PathFollow2D) ← 沿路径移动
    ├── Sprite2D
    └── CollisionShape2D

简单来回巡逻（不用 Path2D）

如果敌人只是在两点之间来回走，不需要 Path2D：

C#
// 敌人在两点之间巡逻
using Godot;

public partial class PatrolEnemy : CharacterBody2D
{
    [Export] private float _speed = 60.0f;
    [Export] private float _patrolDistance = 200.0f;

    private Vector2 _startPosition;
    private int _direction = 1;

    public override void _Ready()
    {
        _startPosition = Position;
    }

    public override void _PhysicsProcess(double delta)
    {
        Velocity = new Vector2(_direction * _speed, Velocity.Y);
        MoveAndSlide();

        // 走到巡逻范围尽头就掉头
        if (Position.X > _startPosition.X + _patrolDistance)
            _direction = -1;
        else if (Position.X < _startPosition.X - _patrolDistance)
            _direction = 1;

        // 碰到墙壁也掉头
        if (IsOnWall())
            _direction *= -1;
    }
}

追踪玩家

敌人检测到玩家后，朝玩家方向移动。这是最常用的敌人行为。

简单追踪

C#
// 敌人追踪玩家
using Godot;

public partial class ChaseEnemy : CharacterBody2D
{
    private const float Speed = 80.0f;
    private Node2D _player;

    public override void _Ready()
    {
        // 找到玩家节点（通过分组）
        _player = GetTree().GetFirstNodeInGroup("players") as Node2D;
    }

    public override void _PhysicsProcess(double delta)
    {
        if (_player != null)
        {
            Vector2 direction = (_player.Position - Position).Normalized();
            Velocity = direction * Speed;
            MoveAndSlide();
        }
    }
}

带检测范围的追踪

不是一开始就追，而是玩家靠近了才追。用 RayCast2D 或者距离检测：

C#
// 带检测范围的追踪敌人
using Godot;

public partial class SmartEnemy : CharacterBody2D
{
    [Export] private float _chaseSpeed = 100.0f;
    [Export] private float _patrolSpeed = 40.0f;
    [Export] private float _detectRange = 200.0f;
    [Export] private float _attackRange = 30.0f;

    private Node2D _player;
    private bool _isChasing = false;

    public override void _Ready()
    {
        _player = GetTree().GetFirstNodeInGroup("players") as Node2D;
    }

    public override void _PhysicsProcess(double delta)
    {
        if (_player == null) return;

        float distanceToPlayer = Position.DistanceTo(_player.Position);

        if (distanceToPlayer < _detectRange)
        {
            _isChasing = true;
        }
        else if (distanceToPlayer > _detectRange * 1.5f)
        {
            // 超出追踪范围的 1.5 倍后放弃追踪
            _isChasing = false;
        }

        if (_isChasing)
        {
            Vector2 direction = (_player.Position - Position).Normalized();
            Velocity = new Vector2(direction.X * _chaseSpeed, Velocity.Y);
        }
        else
        {
            // 原地不动或缓慢巡逻
            Velocity = new Vector2(0, Velocity.Y);
        }

        MoveAndSlide();
    }
}

触发式行为

有些敌人不需要移动，而是在玩家靠近时触发事件（如突然出现、发射子弹）。

使用 Area2D 的信号：

Trap (Area2D)
├── CollisionShape2D    ← 检测区域
└── Sprite2D            ← 陷阱外观
C#
// 陷阱触发
using Godot;

public partial class Trap : Area2D
{
    [Export] private int _damage = 20;

    public override void _Ready()
    {
        BodyEntered += OnBodyEntered;
    }

    private void OnBodyEntered(Node2D body)
    {
        if (body.IsInGroup("players"))
        {
            body.Call("take_damage", _damage);
            // 可以播放动画、音效
        }
    }
}

简单状态机

当敌人有多种行为（巡逻、追踪、攻击、死亡）时，用状态机管理最清晰。

什么是状态机

打个比方：红绿灯就是状态机——它只有三个状态（红、黄、绿），任何时刻只能处于其中一个状态，并且按固定规则切换（红→绿→黄→红）。

敌人的行为也是一样：同一时刻只能做一件事（巡逻、追踪、攻击、死亡），并且按规则切换状态。

C#
// 简单的敌人状态机
using Godot;

public enum EnemyState { Patrol, Chase, Attack, Dead }

public partial class StateMachineEnemy : CharacterBody2D
{
    [Export] private float _patrolSpeed = 40.0f;
    [Export] private float _chaseSpeed = 100.0f;
    [Export] private float _detectRange = 200.0f;
    [Export] private float _attackRange = 30.0f;

    private EnemyState _state = EnemyState.Patrol;
    private Node2D _player;
    private int _patrolDirection = 1;
    private float _hp = 100.0f;

    public override void _Ready()
    {
        _player = GetTree().GetFirstNodeInGroup("players") as Node2D;
    }

    public override void _PhysicsProcess(double delta)
    {
        switch (_state)
        {
            case EnemyState.Patrol:
                PatrolBehavior(delta);
                break;
            case EnemyState.Chase:
                ChaseBehavior(delta);
                break;
            case EnemyState.Attack:
                AttackBehavior(delta);
                break;
            case EnemyState.Dead:
                return; // 什么都不做
        }

        MoveAndSlide();
    }

    private void PatrolBehavior(double delta)
    {
        Velocity = new Vector2(_patrolDirection * _patrolSpeed, Velocity.Y);

        if (IsOnWall())
            _patrolDirection *= -1;

        // 检测到玩家就切换到追踪
        if (_player != null && Position.DistanceTo(_player.Position) < _detectRange)
            _state = EnemyState.Chase;
    }

    private void ChaseBehavior(double delta)
    {
        if (_player == null) { _state = EnemyState.Patrol; return; }

        float dist = Position.DistanceTo(_player.Position);

        // 太远了就放弃
        if (dist > _detectRange * 2.0f)
        {
            _state = EnemyState.Patrol;
            return;
        }

        // 够近了就攻击
        if (dist < _attackRange)
        {
            _state = EnemyState.Attack;
            return;
        }

        Vector2 dir = (_player.Position - Position).Normalized();
        Velocity = new Vector2(dir.X * _chaseSpeed, Velocity.Y);
    }

    private void AttackBehavior(double delta)
    {
        Velocity = Vector2.Zero;
        // 播放攻击动画、造成伤害
        // 攻击结束后回到追踪
        _state = EnemyState.Chase;
    }

    public void TakeDamage(float amount)
    {
        _hp -= amount;
        if (_hp <= 0)
        {
            _state = EnemyState.Dead;
            QueueFree();
        }
    }
}

下一章

敌人行为搞定了，接下来学习精灵动画，让角色和敌人"动起来"。

→ 12. 2D精灵与动画

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贡献者: zefeng.peng,bobokaka
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