2-28 Projectiles Discriminate

今天要來改進Enemy發射Projectile時也同樣會攻擊到Enemy的問題。解決方法是在Projectile中增加條件式，判斷發射Projectile的GameObject所處的Layer。比方說，敵人的Layer是Enemy，那由Enemy Layer的GameObject發射的Projectile，就不應該攻擊到同樣在Enemy Layer的Projectile。

所以首先我們先替玩家角色新增Layer，我們之前一直沒有新增Player。

然後修改Projectile.cs，我們新增一個GameObject名為Shooter，並判斷Collision GameObject的Layer是否不同於Shooter的Layer：

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using System.Collections; using System.Collections.Generic; using UnityEngine;   public class Projectile : MonoBehaviour {    [SerializeField] float projectileSpeed;  [SerializeField] GameObject shooter;  float damageCaused;    public void SetShooter(GameObject shooter){   this.shooter = shooter;  }    public void SetDamage(float damage){   damageCaused = damage;  }    public float GetDefaultLaunchSpeed(){   return projectileSpeed;  }    void OnCollisionEnter(Collision collision){     int layerCollidedWith = collision.gameObject.layer;   // 若被碰撞的物體所處的Layer跟shooter的Layer不同，才會觸發攻擊機制   // 如敵人就不會攻擊到敵人   if (layerCollidedWith != shooter.layer) {    DamageIfDamageable (collision);   }  }    private void DamageIfDamageable(Collision collision){   // 取得Component為IDamageable   Component damageableComponent = collision.gameObject.GetComponent (typeof(IDamageable));   // 若IDamageable存在   if (damageableComponent) {    // 呼叫damageableComponent的TakeDamage方法    (damageableComponent as IDamageable).TakeDamage (damageCaused);   }   // 自我消滅   Destroy(gameObject);  } }

接著，因為Enemy發射Projectile，所以修改Enemy.cs，呼叫Projectile的SetShooter方法：

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using System.Collections; using System.Collections.Generic; using UnityEngine; using UnityEngine.AI; using UnityStandardAssets.Characters.ThirdPerson;   public class Enemy : MonoBehaviour, IDamageable {    [SerializeField] float maxHealthPoints = 100f;  [SerializeField] float attackRadius = 3.0f;  [SerializeField] float chaseRadius = 10.0f;  [SerializeField] float damagePerShot = 9f;  [SerializeField] float secondsBetweenShots = 0.5f;  [SerializeField] GameObject projectileToUse;  [SerializeField] GameObject projectileSocket;  [SerializeField] Vector3 aimOffset = new Vector3(0, 1f, 0);    bool isAttacking = false;  float currentHealthPoint;  AICharacterControl aiCharacterControl = null;  GameObject player;  IEnumerator coroutine;    public float healthAsPercentage{   get{ return currentHealthPoint / maxHealthPoints; }  }    void Start(){   currentHealthPoint = maxHealthPoints;     aiCharacterControl = GetComponent<aicharactercontrol> ();   player = GameObject.FindGameObjectWithTag ("Player");  }    void Update(){   // 計算Player跟Enemy的距離   float distanceToPlayer = Vector3.Distance (player.transform.position, transform.position);   // 若彼此之間的距離小於attackRadius，就讓Enemy開始攻擊Player   if (distanceToPlayer <= attackRadius && !isAttacking) {    isAttacking = true;    coroutine = SpawnProjectile ();    StartCoroutine (coroutine);   }   if (distanceToPlayer > attackRadius && isAttacking) {    isAttacking = false;    StopCoroutine (coroutine);   }   // 若彼此之間的距離小於chaseRadius，就讓Enemy開始追蹤Player   if (distanceToPlayer <= chaseRadius) {    aiCharacterControl.SetTarget (player.transform);   } else {    aiCharacterControl.SetTarget (transform);   }  }    IEnumerator SpawnProjectile(){   while (true) {    yield return new WaitForSeconds (secondsBetweenShots);      // Instantiate可以生成GameObject，Quaternion.identity為方向不進行任何轉向    GameObject newProjectile = Instantiate(projectileToUse, projectileSocket.transform.position, Quaternion.identity);    // 取得Projectile    Projectile projectileComponent = newProjectile.GetComponent<projectile> ();    // 設定Projectile的攻擊威力    projectileComponent.SetDamage(damagePerShot);    // 設定Projectile的Shooter為自己    projectileComponent.SetShooter (gameObject);      // 計算發射Projectile到Player之間的單位向量    Vector3 unitVectorToPlayer = (player.transform.position + aimOffset - projectileSocket.transform.position).normalized;    float projectileSpeed = projectileComponent.GetDefaultLaunchSpeed();    // 將單位向量乘以發射速度，透過velocity將Projectile發射出去吧！    newProjectile.GetComponent<rigidbody> ().velocity = unitVectorToPlayer * projectileSpeed;   }  }    public void TakeDamage(float damage){   // Math.Clamp可以確保數值運算後不會低於最小值或者高於最大值   currentHealthPoint = Mathf.Clamp (currentHealthPoint - damage, 0f, maxHealthPoints);   // 敵人血量低於0就會消失   if (currentHealthPoint <= 0) {    Destroy (gameObject);   }  }    void OnDrawGizmos(){   //繪製攻擊範圍   Gizmos.color = new Color(255f, 0f, 0f, 0.5f);   Gizmos.DrawWireSphere (transform.position, attackRadius);     //繪製移動範圍   Gizmos.color = new Color(0f, 0f, 255f, 0.5f);   Gizmos.DrawWireSphere (transform.position, chaseRadius);  } }   </rigidbody></projectile></aicharactercontrol>

最後，測試遊戲看看Enemy的Projectile是否會攻擊到Enemy。