【Unity3D】发射(RayCast)物理射线(Ray)

1 前言

        碰撞体组件Collider 中介绍了 2 个碰撞体之间的碰撞检测，本文将介绍物理射线与碰撞体之间的碰撞检测。物理射线由 Ray 定义，通过 Physics.RayCast / Physics.RayCastAll 发射射线，返回 RayCastHit 碰撞检测信息。

        射线仅用于检测碰撞，游戏界面不能看见，但用户可以通过 Debug.DrawRay 绘制射线，通过  Debug.DrawLine 绘制线段，它们绘制的射线和线段只能在 Scene 窗口看见，在 Game 窗口看不见。

        1）定义射线

// origin: 起点, direction: 方向
public Ray(Vector3 origin, Vector3 direction)
// 屏幕射线: 以相机位置为起点, 向近平面上鼠标位置方向投射的射线
Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);

        2）发射射线

// ray: 待发射的射线, hitInfo: 碰撞检测信息, maxDistance: 射线发射的最远距离, 返回是否发生碰撞, 只检测第一个碰撞对象
public static bool Raycast(Ray ray)
public static bool Raycast(Ray ray, out RaycastHit hitInfo)
public static bool Raycast(Ray ray, float maxDistance)
public static bool Raycast(Ray ray, out RaycastHit hitInfo, float maxDistance)
// 检查射线射程范围内所有碰撞
public static RaycastHit[] RaycastAll(Ray ray)
public static RaycastHit[] RaycastAll(Ray ray, float maxDistance)

        说明：以上方法是 Physics 类的静态方法，hitInfo 封装了碰撞信息，包含碰撞位置 point、碰撞体 collider 等。

        3）调试射线

// start: 射线起点, dir: 射线方向, color: 射线颜色
public static void DrawRay(Vector3 start, Vector3 dir)
public static void DrawRay(Vector3 start, Vector3 dir, Color color)
// start: 线段起点, end: 线段终点, color: 线段颜色
public static void DrawLine(Vector3 start, Vector3 end)
public static void DrawLine(Vector3 start, Vector3 end, Color color)

        4）区域碰撞检测

// 检验立方体范围内是否有碰撞体
public static bool CheckBox(Vector3 center, Vector3 halfExtents)
public static bool CheckBox(Vector3 center, Vector3 halfExtents, Quaternion orientation, int layermask)
// 检验球体范围内是否有碰撞体
public static bool CheckSphere(Vector3 position, float radius)
public static bool CheckSphere(Vector3 position, float radius, int layerMask)
// 检验胶囊体范围内是否有碰撞体
public static bool CheckCapsule(Vector3 start, Vector3 end, float radius)
public static bool CheckCapsule(Vector3 start, Vector3 end, float radius, int layermask)

        说明：以上方法是 Physics 类的静态方法。

        5）投射物体

// 投射立方体
public static bool BoxCast(Vector3 center, Vector3 halfExtents, Vector3 direction)
public static bool BoxCast(Vector3 center, Vector3 halfExtents, Vector3 direction, out RaycastHit hitInfo, Quaternion orientation, float maxDistance, int layerMask)
public static RaycastHit[] BoxCastAll(Vector3 center, Vector3 halfExtents, Vector3 direction)
public static RaycastHit[] BoxCastAll(Vector3 center, Vector3 halfExtents, Vector3 direction, Quaternion orientation, float maxDistance, int layermask)
// 投射球体
public static bool SphereCast(Ray ray, float radius)
public static bool SphereCast(Ray ray, float radius, out RaycastHit hitInfo, float maxDistance, int layerMask)
public static bool SphereCast(Vector3 origin, float radius, Vector3 direction, out RaycastHit hitInfo)
public static bool SphereCast(Vector3 origin, float radius, Vector3 direction, out RaycastHit hitInfo, float maxDistance, int layerMask)
public static RaycastHit[] SphereCastAll(Ray ray, float radius)
public static RaycastHit[] SphereCastAll(Ray ray, float radius, float maxDistance, int layerMask)
public static RaycastHit[] SphereCastAll(Vector3 origin, float radius, Vector3 direction)
public static RaycastHit[] SphereCastAll(Vector3 origin, float radius, Vector3 direction, float maxDistance, int layerMask)
// 投射胶囊体
public static bool CapsuleCast(Vector3 point1, Vector3 point2, float radius, Vector3 direction)
public static bool CapsuleCast(Vector3 point1, Vector3 point2, float radius, Vector3 direction, out RaycastHit hitInfo, float maxDistance, int layerMask)
public static RaycastHit[] CapsuleCastAll(Vector3 point1, Vector3 point2, float radius, Vector3 direction)
public static RaycastHit[] CapsuleCastAll(Vector3 point1, Vector3 point2, float radius, Vector3 direction, float maxDistance, int layermask)

        说明：以上方法是 Physics 类的静态方法。 

2 应用

        1）游戏对象

        游戏对象的 Transform 组件参数如下：

Name	Type	Position	Rotation	Scale	Color
Plane	Plane	(0, 0, 0)	(0, 0, 0)	(2, 2, 2)	#B8B2B2FF
Cube1	Cube	(-3, 0.5, 3)	(0, 0, 0)	(1, 1, 1)	#F91D1DFF
Cube2	Cube	(0, 0.5, 3)	(0, 0, 0)	(1, 1, 1)	#F91D1DFF
Cube3	Cube	(3, 0.5, 3)	(0, 0, 0)	(1, 1, 1)	#F91D1DFF
Cube4	Cube	(-3, 0.5, 0)	(0, 0, 0)	(1, 1, 1)	#F91D1DFF
Cube5	Cube	(0, 0.5, 0)	(0, 0, 0)	(1, 1, 1)	#F91D1DFF
Cube6	Cube	(3, 0.5, 0)	(0, 0, 0)	(1, 1, 1)	#F91D1DFF
Cube7	Cube	(-3, 0.5, -3)	(0, 0, 0)	(1, 1, 1)	#F91D1DFF
Cube8	Cube	(0, 0.5, -3)	(0, 0, 0)	(1, 1, 1)	#F91D1DFF
Cube9	Cube	(3, 0.5, -3)	(0, 0, 0)	(1, 1, 1)	#F91D1DFF
Bullet	Sphere	(0, 0.5, -5)	(0, 0, 0)	(0.3, 0.3, 0.3)	#FDF723FF
BulletCreater	Empty	(0, 0, 0)	(0, 0, 0)	(1, 1, 1)	——

        补充：Cube1~Cube9 和 Bullet 都添加了 Rigidbody 刚体组件，将 Bullet 拖拽至 Assets 窗口的 Resources/Prefabs 目录下，生成预设体（prefab），再删除 Hierarchy 窗口下 Bullet 对象。

        2）脚本组件

        给 BulletCreater 游戏对象添加 RayController 脚本组件。

        RayController.cs

using UnityEngine;

public class RayController : MonoBehaviour {
	private GameObject bulletPrefab; // 炮弹预设体
	private RaycastHit hit; // 碰撞信息

	void Start () {
		bulletPrefab = (GameObject) Resources.Load("Prefabs/Bullet");
		hit = new RaycastHit();
	}

	void Update () {
		if (Input.GetMouseButtonDown(0)) {
			Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
			if (Physics.Raycast(ray, out hit, 100)) {
				// ray.origin = Camera.main.transform.position
				GameObject bullet = Instantiate(bulletPrefab, ray.origin, Quaternion.identity); // 通过预设体创建炮弹
				bullet.GetComponent<Rigidbody>().velocity = ray.direction * 100;
				Destroy(bullet, 3);
			}
		}
	}
}

        3）运行效果