在做HTC的VIVE VR开发过程中，经常会用到手柄的操作。而对于手柄发射射线选中物体最是经常用到。

有时候我们希望得到手柄射线与物体碰撞的碰撞点坐标，（如：有时做射击时希望在碰撞点加点动画特效什么的）

如果不知道碰撞点，那么特效可能就不知道往哪里放。

其实要获得碰撞点很简单，下面类是SteamVR中自带的类SteamVR_LaserPointer ，我们只用对这个类稍微修改下，

如红下面代码中红色字体部分，就是把这个类里面的RaycastHit。碰撞对象作为公用类型公布出来，就可以了。而碰撞点就

是这个对象的 point 属性。

//======= Copyright (c) Valve Corporation, All rights reserved. ===============

using UnityEngine;
using System.Collections;


public struct PointerEventArgs
{
    public uint controllerIndex;
    public uint flags;
    public float distance;
    public Transform target;
}

public delegate void PointerEventHandler(object sender, PointerEventArgs e);

public class SteamVR_LaserPointer : MonoBehaviour
{
    public bool active = true;
    public Color color;
    public float thickness = 0.002f;
    public GameObject holder;
    public GameObject pointer;
    bool isActive = false;
    public bool addRigidBody = false;
    public Transform reference;
    public event PointerEventHandler PointerIn;
    public event PointerEventHandler PointerOut;
    /// <summary>
    /// 射线碰撞的相关信息
    /// </summary>
    public RaycastHit rayhit;
    Transform previousContact = null;
// Use this for initialization
void Start ()
    {
        holder = new GameObject();
        holder.transform.parent = this.transform;
        holder.transform.localPosition = Vector3.zero;
holder.transform.localRotation = Quaternion.identity;


pointer = GameObject.CreatePrimitive(PrimitiveType.Cube);
        pointer.transform.parent = holder.transform;
        pointer.transform.localScale = new Vector3(thickness, thickness, 100f);
        pointer.transform.localPosition = new Vector3(0f, 0f, 50f);
pointer.transform.localRotation = Quaternion.identity;
BoxCollider collider = pointer.GetComponent<BoxCollider>();
        if (addRigidBody)
        {
            if (collider)
            {
                collider.isTrigger = true;
            }
            Rigidbody rigidBody = pointer.AddComponent<Rigidbody>();
            rigidBody.isKinematic = true;
        }
        else
        {
            if(collider)
            {
                Object.Destroy(collider);
            }
        }
        Material newMaterial = new Material(Shader.Find("Unlit/Color"));
        newMaterial.SetColor("_Color", color);
        pointer.GetComponent<MeshRenderer>().material = newMaterial;
}


    public virtual void OnPointerIn(PointerEventArgs e)
    {
        if (PointerIn != null)
            PointerIn(this, e);
    }


    public virtual void OnPointerOut(PointerEventArgs e)
    {
        if (PointerOut != null)
            PointerOut(this, e);
    }




    // Update is called once per frame
void Update ()
    {
        if (!isActive)
        {
            isActive = true;
            this.transform.GetChild(0).gameObject.SetActive(true);
        }


        float dist = 100f;


        SteamVR_TrackedController controller = GetComponent<SteamVR_TrackedController>();


        Ray raycast = new Ray(transform.position, transform.forward);
        RaycastHit hit;
        bool bHit = Physics.Raycast(raycast, out hit);
        rayhit = hit;
        if (previousContact && previousContact != hit.transform)
        {
            PointerEventArgs args = new PointerEventArgs();
            if (controller != null)
            {
                args.controllerIndex = controller.controllerIndex;
            }
            args.distance = 0f;
            args.flags = 0;
            args.target = previousContact;
            OnPointerOut(args);
            previousContact = null;
        }
        if(bHit && previousContact != hit.transform)
        {
            PointerEventArgs argsIn = new PointerEventArgs();
            if (controller != null)
            {
                argsIn.controllerIndex = controller.controllerIndex;
            }
            argsIn.distance = hit.distance;
            argsIn.flags = 0;
            argsIn.target = hit.transform;
            OnPointerIn(argsIn);
            previousContact = hit.transform;
        }
        if(!bHit)
        {
            previousContact = null;
        }
        if (bHit && hit.distance < 100f)
        {
            dist = hit.distance;
        }


        if (controller != null && controller.triggerPressed)
        {
            pointer.transform.localScale = new Vector3(thickness * 5f, thickness * 5f, dist);
        }
        else
        {
            pointer.transform.localScale = new Vector3(thickness, thickness, dist);
        }
        pointer.transform.localPosition = new Vector3(0f, 0f, dist/2f);
    }
}