Unity3d之坦克对战游戏 AI设计
作业要求
- 使用“感知-思考-行为”模型，建模 AI 坦克
- 场景中要放置一些障碍阻挡对手视线
- 坦克需要放置一个矩阵包围盒触发器，以保证 AI 坦克能使用射线探测对手方位
- AI 坦克必须在有目标条件下使用导航，并能绕过障碍。（失去目标时策略自己思考）
- 实现人机对战
这次作业的具体要求如上面所述，简单来说就是实现一个AI坦克，能够搜索玩家并且发现玩家之后会追踪玩家并且发射子弹，同时满足能够避开障碍物。
演示视频
请移步： https://www.bilibili.com/video/av25190155/
游戏实现
游戏场景设计
这次作业参考了去年师兄的作品，利用官方教程Tanks! Tutorial里面的模型构建了自己的游戏场景。效果如下：
接着打开Window -> Navigation，设置游戏对象的Navigation，如果是障碍物则设置Navigation Area为not walkable。如下：
接着进行Bake，以便AI寻路。
游戏关键代码解析
AI坦克的状态图如下：
为了实现坦克自动寻路，需要为坦克对象添加NavMeshAgent组件。这么做是为了当AI坦克发现玩家之后，只需要为NavMeshAgent设置destination，AI坦克便能够自动寻路，前往玩家所在位置。
从状态图中可以看出，一开始AI坦克如果在自己附近没有发现玩家，则会进入巡逻状态，这里我预先设置了几个点，AI坦克会随机选取一个作为目的点，并自动寻路移动到目的点，并继续下次巡逻；在这个过程中如果AI坦克发现了附近的玩家，则会进行追捕，我把玩家的位置设置为AI坦克的目的点，从而使AI坦克自动向玩家方向移动；当距离进入了AI坦克的射程范围，则AI坦克会通过协程每隔一秒发射一颗子弹。
相关代码：
public class AITank : Tank {
public delegate void recycle(GameObject tank);
public static event recycle recycleEvent;
private Vector3 target;
private bool gameover;
// 巡逻点
private static Vector3[] points = { new Vector3(37.6f,0,0), new Vector3(40.9f,0,39), new Vector3(13.4f, 0, 39),
new Vector3(13.4f, 0, 21), new Vector3(0,0,0), new Vector3(-20,0,0.3f), new Vector3(-20, 0, 32.9f),
new Vector3(-37.5f, 0, 40.3f), new Vector3(-37.5f,0,10.4f), new Vector3(-40.9f, 0, -25.7f), new Vector3(-15.2f, 0, -37.6f),
new Vector3(18.8f, 0, -37.6f), new Vector3(39.1f, 0, -18.1f)
};
private int destPoint = 0;
private NavMeshAgent agent;
private bool isPatrol = false;
private void Awake()
{
destPoint = UnityEngine.Random.Range(0, 13);
}
// Use this for initialization
void Start () {
setHp(100f);
StartCoroutine(shoot());
agent = GetComponent();
}
private IEnumerator shoot()
{
while (!gameover)
{
for(float i = 1; i > 0; i -= Time.deltaTime)
{
yield return 0;
}
// 当敌军坦克距离玩家坦克不到20时开始射击
if(Vector3.Distance(transform.position, target) < 20)
{
GameObjectFactory mf = Singleton.Instance;
GameObject bullet = mf.getBullet(tankType.Enemy);
bullet.transform.position = new Vector3(transform.position.x, 1.5f, transform.position.z) + transform.forward * 1.5f;
bullet.transform.forward = transform.forward;
// 发射子弹
Rigidbody rb = bullet.GetComponent();
rb.AddForce(bullet.transform.forward * 20, ForceMode.Impulse);
}
}
}
// Update is called once per frame
void Update () {
gameover = GameDirector.getInstance().currentSceneController.isGameOver();
if (!gameover)
{
target = GameDirector.getInstance().currentSceneController.getPlayerPos();
if (getHp() <= 0 && recycleEvent != null)
{//如果npc坦克被摧毁，则回收它
recycleEvent(this.gameObject);
}
else
{
if(Vector3.Distance(transform.position, target) <= 30)
{
isPatrol = false;
//否则向玩家坦克移动
agent.autoBraking = true;
agent.SetDestination(target);
}
else
{
patrol();
}
}
}
else
{
NavMeshAgent agent = GetComponent();
agent.velocity = Vector3.zero;
agent.ResetPath();
}
}
private void patrol()
{
if(isPatrol)
{
if(!agent.pathPending && agent.remainingDistance < 0.5f)
GotoNextPoint();
}
else
{
agent.autoBraking = false;
GotoNextPoint();
}
isPatrol = true;
}
private void GotoNextPoint()
{
agent.SetDestination(points[destPoint]);
destPoint = (destPoint + 1) % points.Length;
}
}
子弹类的要点在于通过OnCollisionEnter事件判断在子弹碰撞到其他物体时，爆炸范围内的所有碰撞体对象，如果子弹是AI坦克发射的并且碰撞体为玩家，则玩家坦克会扣血，子弹失活回收；如果子弹是玩家发射并且碰撞体是AI坦克，则AI坦克扣血。还要注意当子弹落地时（我通过transform.position.y < 0 判断）应该把子弹回收。
public class Bullet : MonoBehaviour {
// 子弹伤害半径
public float explosionRadius = 3f;
private tankType type;
public void setTankType(tankType type)
{
this.type = type;
}
private void Update()
{
if(this.transform.position.y < 0 && this.gameObject.activeSelf)
{
GameObjectFactory mf = Singleton.Instance;
// 落地爆炸
ParticleSystem explosion = mf.getPs();
explosion.transform.position = transform.position;
explosion.Play();
mf.recycleBullet(this.gameObject);
}
}
void OnCollisionEnter(Collision other)
{
// 获得单实例工厂
GameObjectFactory mf = Singleton.Instance;
ParticleSystem explosion = mf.getPs();
explosion.transform.position = transform.position;
// 获取爆炸范围内的所有碰撞体
Collider[] colliders = Physics.OverlapSphere(transform.position, explosionRadius);
for(int i = 0; i < colliders.Length; i++)
{
if(colliders[i].tag == "tankPlayer" && this.type == tankType.Enemy || colliders[i].tag == "tankEnemy" && this.type == tankType.Player)
{
// 根据击中坦克与爆炸中心的距离计算伤害值
float distance = Vector3.Distance(colliders[i].transform.position, transform.position);//被击中坦克与爆炸中心的距离
float hurt = 100f / distance;
float current = colliders[i].GetComponent().getHp();
c`这里写代码片`olliders[i].GetComponent().setHp(current - hurt);
}
}
explosion.Play();
if (this.gameObject.activeSelf)
{
mf.recycleBullet(this.gameObject);
}
}
}
这个项目中我通过单实例工厂GameObjectFactory来统一管理玩家player、 AI坦克、子弹、爆炸粒子系统等游戏对象，实现方法与老师前面课上讲的内容一致。通过Dictionary来维护。
public class GameObjectFactory : MonoBehaviour {
// 玩家
public GameObject player;
// npc
public GameObject tank;
// 子弹
public GameObject bullet;
// 爆炸粒子系统
public ParticleSystem ps;
private Dictionary<int, GameObject> usingTanks;
private Dictionary<int, GameObject> freeTanks;
private Dictionary<int, GameObject> usingBullets;
private Dictionary<int, GameObject> freeBullets;
private List psContainer;
private void Awake()
{
usingTanks = new Dictionary<int, GameObject>();
freeTanks = new Dictionary<int, GameObject>();
usingBullets = new Dictionary<int, GameObject>();
freeBullets = new Dictionary<int, GameObject>();
psContainer = new List();
}
// Use this for initialization
void Start () {
//回收坦克的委托事件
AITank.recycleEvent += recycleTank;
}
public GameObject getPlayer()
{
return player;
}
public GameObject getTank()
{
if(freeTanks.Count == 0)
{
GameObject newTank = Instantiate(tank);
usingTanks.Add(newTank.GetInstanceID(), newTank);
//在一个随机范围内设置坦克位置
newTank.transform.position = new Vector3(Random.Range(-100, 100), 0, Random.Range(-100, 100));
return newTank;
}
foreach (KeyValuePair<int, GameObject> pair in freeTanks)
{
pair.Value.SetActive(true);
freeTanks.Remove(pair.Key);
usingTanks.Add(pair.Key, pair.Value);
pair.Value.transform.position = new Vector3(Random.Range(-100, 100), 0, Random.Range(-100, 100));
return pair.Value;
}
return null;
}
public GameObject getBullet(tankType type)
{
if (freeBullets.Count == 0)
{
GameObject newBullet = Instantiate(bullet);
newBullet.GetComponent().setTankType(type);
usingBullets.Add(newBullet.GetInstanceID(), newBullet);
return newBullet;
}
foreach (KeyValuePair<int, GameObject> pair in freeBullets)
{
pair.Value.SetActive(true);
pair.Value.GetComponent().setTankType(type);
freeBullets.Remove(pair.Key);
usingBullets.Add(pair.Key, pair.Value);
return pair.Value;
}
return null;
}
public ParticleSystem getPs()
{
for(int i = 0; i < psContainer.Count; i++)
{
if (!psContainer[i].isPlaying) return psContainer[i];
}
ParticleSystem newPs = Instantiate(ps);
psContainer.Add(newPs);
return newPs;
}
public void recycleTank(GameObject tank)
{
usingTanks.Remove(tank.GetInstanceID());
freeTanks.Add(tank.GetInstanceID(), tank);
tank.GetComponent().velocity = new Vector3(0, 0, 0);
tank.SetActive(false);
}
public void recycleBullet(GameObject bullet)
{
usingBullets.Remove(bullet.GetInstanceID());
freeBullets.Add(bullet.GetInstanceID(), bullet);
bullet.GetComponent().velocity = new Vector3(0, 0, 0);
bullet.SetActive(false);
}
} 然后为了实现一个比较好的游戏体验，我实现了一个MainCameraControl来控制主摄像机的移动跟随效果，并且能够通过游戏场景中所有坦克的距离大小来设置摄像机的Size，从而视觉体验更佳~具体实现见下面代码，注释比较清楚~
public class MainCameraControl : MonoBehaviour {
public float m_DampTime = 0.2f; // 相机refocus的时间
public float m_ScreenEdgeBuffer = 4f; // 最靠近边界的坦克与边界之间的缓冲大小
public float m_MinSize = 6.5f; // 相机Size最小值
[HideInInspector] public List m_Targets; // 保存所有坦克的transform
private Camera m_Camera;
private float m_ZoomSpeed;
private Vector3 m_MoveVelocity;
private Vector3 m_DesiredPosition;
private void Awake()
{
m_Camera = Camera.main;
}
public void setTarget(Transform transform)
{
m_Targets.Add(transform);
}
private void FixedUpdate()
{
// 把相机移动到希望的位置
Move();
// 改变相机size
Zoom();
}
private void Move()
{
FindAveragePosition();
transform.position = Vector3.SmoothDamp(transform.position, m_DesiredPosition, ref m_MoveVelocity, m_DampTime);
}
// 计算平均位置
private void FindAveragePosition()
{
Vector3 averagePos = new Vector3();
int numTargets = 0;
for (int i = 0; i < m_Targets.Count; i++)
{
if (!m_Targets[i].gameObject.activeSelf)
continue;
averagePos += m_Targets[i].position;
numTargets++;
}
if (numTargets > 0)
averagePos /= numTargets;
averagePos.y = transform.position.y;
m_DesiredPosition = averagePos;
}
private void Zoom()
{
float requiredSize = FindRequiredSize();
m_Camera.orthographicSize = Mathf.SmoothDamp(m_Camera.orthographicSize, requiredSize, ref m_ZoomSpeed, m_DampTime);
}
// 计算合适的Size
private float FindRequiredSize()
{
Vector3 desiredLocalPos = transform.InverseTransformPoint(m_DesiredPosition);
float size = 0f;
for (int i = 0; i < m_Targets.Count; i++)
{
if (!m_Targets[i].gameObject.activeSelf)
continue;
Vector3 targetLocalPos = transform.InverseTransformPoint(m_Targets[i].position);
Vector3 desiredPosToTarget = targetLocalPos - desiredLocalPos;
size = Mathf.Max(size, Mathf.Abs(desiredPosToTarget.y));
size = Mathf.Max(size, Mathf.Abs(desiredPosToTarget.x) / m_Camera.aspect);
}
size += m_ScreenEdgeBuffer;
size = Mathf.Max(size, m_MinSize);
return size;
}
// 初始化相机
public void SetStartPositionAndSize()
{
FindAveragePosition();
transform.position = m_DesiredPosition;
m_Camera.orthographicSize = FindRequiredSize();
}
} 场记SceneController内容也比较简单，主要负责通知工厂初始化各种游戏对象，如player、AI坦克等，并初始化主摄像机，然后实现IUserAction接口中声明的函数即可。
public class SceneController : MonoBehaviour, IUserAction {
public GameObject player;
private bool gameOver = false;
private int enemyCount = 6;
private GameObjectFactory mf;
private MainCameraControl cameraControl;
private void Awake()
{
GameDirector director = GameDirector.getInstance();
director.currentSceneController = this;
mf = Singleton.Instance;
player = mf.getPlayer();
cameraControl = GetComponent();
cameraControl.setTarget(player.transform);
}
// Use this for initialization
void Start () {
for(int i = 0; i < enemyCount; i++)
{
GameObject gb = mf.getTank();
cameraControl.setTarget(gb.transform);
}
Player.destroyEvent += setGameOver;
// 初始化相机位置
cameraControl.SetStartPositionAndSize();
}
// 更新相机位置
void Update () {
Camera.main.transform.position = new Vector3(player.transform.position.x, 15, player.transform.position.z);
}
public Vector3 getPlayerPos()
{
return player.transform.position;
}
public bool isGameOver()
{
return gameOver;
}
public void setGameOver()
{
gameOver = true;
}
public void moveForward()
{
player.GetComponent().velocity = player.transform.forward * 20;
}
public void moveBackWard()
{
player.GetComponent().velocity = player.transform.forward * -20;
}
public void turn(float offsetX)
{
float y = player.transform.localEulerAngles.y + offsetX * 5;
float x = player.transform.localEulerAngles.x;
player.transform.localEulerAngles = new Vector3(x, y, 0);
}
public void shoot()
{
GameObject bullet = mf.getBullet(tankType.Player);
// 设置子弹位置
bullet.transform.position = new Vector3(player.transform.position.x, 1.5f, player.transform.position.z) + player.transform.forward * 1.5f;
// 设置子弹方向
bullet.transform.forward = player.transform.forward;
// 发射子弹
Rigidbody rb = bullet.GetComponent();
rb.AddForce(bullet.transform.forward * 20, ForceMode.Impulse);
}
} 完整代码请到我的github上查看：https://github.com/CarolSum/Unity3d-Learning/tree/master/hw9