3-10 Create An Area Of Effect Ability

延續上一章跟大家介紹特殊技能系統，本章要製作範圍攻擊的技能，如果大家看不懂下面做的事情，請先看前一章唷。
3-9 Special Abilities System Overview

https://rpgcorecombat.blogspot.tw/2017/12/3-9-special-abilities-system-overview.html

首先，請大家在Special Abilities資料夾中新增Area Effect資料夾。

在Area Effect資料夾中，新增兩個Script，AreaEffectBehaviour跟AreaEffectConfig。

由於本次要製作範圍攻擊，請大家先閱讀一下Untiy官方的介紹：
https://docs.unity3d.com/ScriptReference/Physics.SphereCastAll.html

Casts a sphere against all colliders in the scene and returns detailed information on each collider which was hit. This is useful when a Raycast does not give enough precision, because you want to find out if an object of a specific size, such as a character, will be able to move somewhere without colliding with anything on the way.

簡而言之，就是可以對場景中投射出一個球體，並返回所有碰撞到這個球體的詳細訊息。比方說我想要測試看看特定大小GameObjecy如Player角色，是否能夠在某處和其他的物件碰撞，就能使用SphereCastAll測試看看，本章要介紹的範圍攻擊亦能適用。可惜找不太到中文教學，似乎撰寫這方面介紹的中文文章不多。

AreaEffectBehaviour.cs：

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using RPG.Core;

namespace RPG.Character{
 public class AreaEffectBehaviour : MonoBehaviour, ISpecialAbility {

  AreaEffectConfig config;

  public void SetConfig(AreaEffectConfig config){
   this.config = config;
  }

  public void Use(AbilityParams useParams){
   RaycastHit[] hits = Physics.SphereCastAll (
                        transform.position,  // 以Player為中心點
                        config.GetRadius (), // 掃描的球體半徑範圍
                        Vector3.up,    // 掃描的方向不重要，因為我們發動的是Player為原點的範圍技
                        config.GetRadius ()  // 掃描距離設定成跟掃描半徑一樣即可
                       );

   foreach (RaycastHit hit in hits) {
    Enemy enemy = hit.collider.gameObject.GetComponent ();
    if (enemy != null) {
     float damageToDeal = useParams.baseDamage + config.GetDamageToEachTarget ();
     enemy.TakeDamage (damageToDeal);
    }
   }

  }

  // Use this for initialization
  void Start () {

  }

 }
}

AreaEffectConfig.cs：

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

namespace RPG.Character{
 [CreateAssetMenu(menuName= ("RPG/Special Ability/Area Effect"))]
 public class AreaEffectConfig : SpecialAbilityConfig {
  [Header("Area Effect Specific")]
  [SerializeField] float radius = 5f;
  [SerializeField] float damageToEachTarget = 15f;

  public override ISpecialAbility AddComponent (GameObject gameObjectAttachTo){
   var behaviourComponent = gameObjectAttachTo.AddComponent ();
   behaviourComponent.SetConfig (this);

   return behaviourComponent;
  }

  public float GetDamageToEachTarget(){
   return damageToEachTarget;
  }

  public float GetRadius(){
   return radius;
  }

 }
}

很簡單吧！只要有特殊技能系統，往後要再新增各種不同類型的技能都非常容易跟方便。接著，在Project視窗Create/RPG/Special Ability/Area Effect。