通过射线与物体的交互

1.鼠标平面拖拽物体

Plane movePlane;
float fixedDistance=2f;
float hitDist, t;
Ray camRay;
Vector3 startPos, point, corPoint;

void OnMouseDown (){
    startPos = transform.position; // save position in case draged to invalid place
    movePlane = new Plane(-Camera.main.transform.forward,transform.position); // find a parallel plane to the camera based on obj start pos;
}

void OnMouseDrag (){
    camRay = Camera.main.ScreenPointToRay(Input.mousePosition); // shoot a ray at the obj from mouse screen point

    if (movePlane.Raycast(camRay,out hitDist)){ // finde the collision on movePlane
        point = camRay.GetPoint(hitDist); // define the point on movePlane
        t=-(fixedDistance-camRay.origin.y)/(camRay.origin.y-point.y); // the x,y or z plane you want to be fixed to
        corPoint.x=camRay.origin.x+(point.x-camRay.origin.x)*t; // calculate the new point t futher along the ray
        corPoint.y=camRay.origin.y+(point.y-camRay.origin.y)*t;
        corPoint.z=camRay.origin.z+(point.z-camRay.origin.z)*t;
        transform.position = corPoint; 
    }
}

2.当射线碰撞目标为boot类型的物品 ，执行拾取操作(仅作参考)

    // Update is called once per frame
    void Update () 
    {
        if(Input.GetMouseButton(0))
        {
            Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);//从摄像机发出到点击坐标的射线
            RaycastHit hitInfo;
            if(Physics.Raycast(ray,out hitInfo))
            {
                Debug.DrawLine(ray.origin,hitInfo.point);//划出射线，只有在scene视图中才能看到
                GameObject gameObj = hitInfo.collider.gameObject;
                Debug.Log("click object name is " + gameObj.name);
                if(gameObj.tag == "boot")//当射线碰撞目标为boot类型的物品 ，执行拾取操作
                {
                    Debug.Log("pick up!");
                }
            }
        }
    }

3.重置物体位移方法，脱卡需要放到摄像机下

    public static void ResetPosition(GameObject ModelSelf, GameObject target, Vector3 parentOffset)
    {
        if (target == Camera.main.gameObject)
        {
            ModelSelf.transform.parent = target.transform;
            ModelSelf.transform.localPosition = Vector3.zero + parentOffset;
            ModelSelf.transform.localRotation = Quaternion.identity;
        }
        else
        {
            ModelSelf.transform.parent = target.transform;
            ModelSelf.transform.localPosition = Vector3.zero;
            ModelSelf.transform.localRotation = Quaternion.identity;
        }
    }

4实例，小球找同颜色父物体

  

完整代码

using System.Collections;
using UnityEngine;

public class DragMeOnPlane : MonoBehaviour
{
    Plane movePlane;
    float fixedDistance = 1f; //y aixs offset
    float hitDist, t;
    Ray cameraRay;
    Vector3 startPos, point, corPoint;
    public float xLimit = 3f;  //默认限制区域为3*3平面
    public float zLimit = 3f;

    public Transform initPosition;      //初始位置
    public Transform targetPosition;    //目标位置

    bool isFindParent = false;

    void OnMouseDown()
    {
        startPos = transform.position; // save position in case draged to invalid place
        movePlane = new Plane(-Camera.main.transform.forward, transform.position); // find a parallel plane to the camera based on obj start pos;
    }

    void OnMouseDrag()
    {
        cameraRay = Camera.main.ScreenPointToRay(Input.mousePosition); // shoot a ray at the obj from mouse screen point

        if (movePlane.Raycast(cameraRay, out hitDist))
        {
            if (!isFindParent)
            {
                // finde the collision on movePlane
                point = cameraRay.GetPoint(hitDist); // define the point on movePlane
                t = -(fixedDistance - cameraRay.origin.y) / (cameraRay.origin.y - point.y); // the x,y or z plane you want to be fixed to

                var tempX = cameraRay.origin.x + (point.x - cameraRay.origin.x) * t;   // calculate the new point t futher along the ray
                var tempZ = cameraRay.origin.z + (point.z - cameraRay.origin.z) * t;
                corPoint.x = Mathf.Clamp(tempX, -xLimit, xLimit);
                corPoint.z = Mathf.Clamp(tempZ, -zLimit, zLimit);
                corPoint.y = cameraRay.origin.y + (point.y - cameraRay.origin.y) * t;

                transform.position = corPoint; 
            }
            else
            {
                transform.localPosition = Vector3.zero;
            }
        }
    }

    void OnTriggerEnter(Collider game)//测试是否触发触发器
    {
        print("Enter " + game.name);

        if(game.name.Equals(targetPosition.name))
        {
            isFindParent = true;
            Utility.ResetPosition(gameObject, targetPosition.gameObject, Vector3.zero);
        }
        else
        {
            isFindParent = true;
            Utility.ResetPosition(gameObject, initPosition.gameObject, Vector3.zero);
            StartCoroutine(ResetIsFindParent());
        }
    }

    IEnumerator ResetIsFindParent()
    {
        yield return new WaitForSeconds(1f);
        isFindParent = false;
    }
}

 5物体碰撞知识参考 http://m.manew.com/thread-30342-1-1.html