关于API看一下链接

http://game.ceeger.com/Script/Physics/Physics.Raycast.html

? static function Raycast (origin : Vector3, direction : Vector3, out hitInfo : RaycastHit, distance : float = Mathf.Infinity, layerMask : int = kDefaultRaycastLayers) : bool

Parameters参数

• origin
  The starting point of the ray in world coordinates.
  在世界坐标，射线的起始点。
• direction
  The direction of the ray.
  射线的方向。
• distance
  The length of the ray
  射线的长度。
• hitInfo
  If true is returned, hitInfo will contain more information about where the collider was hit (See Also: RaycastHit).
  如果返回true，hitInfo将包含碰到器碰撞的更多信息。
• layerMask
  A Layer mask that is used to selectively ignore colliders when casting a ray. 
  只选定Layermask层内的碰撞器，其它层内碰撞器忽略。
  
  

1.注意：如果从一个球型体的内部到外部用光线投射，返回为假

2.layerMask层的选择和屏蔽

首先 看第一个 如果一个点在碰撞体内部，向外部射，

先写一个脚本

using UnityEngine;
using System.Collections;

public class Demo2 : MonoBehaviour {
	public float XStartPos = 0f;
	public float YStartPos = 0f;
	public float ZStartPos = 0f;

	public float XEndPos = 0f;
	public float YEndPos = 0f;
	public float ZEndPos = 0f;


	private Vector3 startPos;
	private Vector3 endPos;

	private Vector3 direction;
	private float distance;
	// Use this for initialization
	void Start () {

		startPos = new Vector3 (XStartPos, YStartPos, ZStartPos);
		endPos = new Vector3 (XEndPos, YEndPos, ZEndPos);

		direction = (endPos - startPos).normalized;
		distance = Vector3.Distance (startPos, endPos);

	}
	
	// Update is called once per frame
	void Update () {
		Debug.DrawLine (startPos, endPos, Color.red);
		RaycastHit hit;
		if (!Physics.Raycast (startPos, direction, out hit, distance)) {
			Debug.Log ("false");	
		} 
		else
		{
			Debug.Log ("yes   " + hit.collider.name);
		}
	}
}

再建一个cube2，startPos依然在cube1内，但endPos在cube2内，运行结果表明 yes  cube2

也就是说  射线由内部向外部射 是不识别自己的碰撞体，但是识别其他的碰撞体。

第二个问题关于射线层的选择和屏蔽

修改一下脚本

using UnityEngine;
using System.Collections;

public class Demo3 : MonoBehaviour {
	public float XStartPos = 0f;
	public float YStartPos = 0f;
	public float ZStartPos = 0f;

	public float XEndPos = 0f;
	public float YEndPos = 0f;
	public float ZEndPos = 0f;


	private Vector3 startPos;
	private Vector3 endPos;

	private Vector3 direction;
	private float distance;
	// Use this for initialization
	void Start () {

		startPos = new Vector3 (XStartPos, YStartPos, ZStartPos);
		endPos = new Vector3 (XEndPos, YEndPos, ZEndPos);

		direction = (endPos - startPos).normalized;
		distance = Vector3.Distance (startPos, endPos);

	}
	
	// Update is called once per frame
	void Update () {
		Debug.DrawLine (startPos, endPos, Color.red);
		RaycastHit hit;
		LayerMask l = 1 << LayerMask.NameToLayer("cube1");
		if (Physics.Raycast (startPos, direction, out hit, distance, l)) {
			Debug.Log ("yes   " + hit.collider.name);
		} 
		else
		{
			Debug.Log ("false");
		}
	}
}

自行比对

只与cube1层碰撞

Physics.Raycast (startPos, direction, out hit, distance, l)

Physics.Raycast (startPos, direction, out hit, distance, ~l)

Physics.Raycast (startPos, direction, out hit, distance, 1 << LayerMask.NameToLayer("cube2") | 1 << LayerMask.NameToLayer("cube3"))

Physics.Raycast (startPos, direction, out hit, distance,~(1 << LayerMask.NameToLayer("cube2") | 1 << LayerMask.NameToLayer("cube3")))

Unity－Physics.Raycast