我們經常要在unity中實現，滑鼠點選物體後，選中物體。然後物體跟隨滑鼠，直到拖拽到指定物體位置，也就是吸附到指定物體上去。

（1）此案例中有兩個物體。

（2）tougu001和tougu002,附加的程式碼分別是 BLtougu001和BLTriggerTouGu002

（3）tougu001 Inspector面板如下：

（4）tougu002 Inspector面板如下：

（5）tougu001 程式碼

using UnityEngine;
using System.Collections;

public class BLtougu001 : MonoBehaviour {
    public BLTriggerTouGu002 m_BLTriggerTouGu002;

    public float mousestate = 0f;

    public Vector3 V3;

    public Camera cam;

    RaycastHit hit;
    // Use this for initialization
    void Start () {
        V3 = transform.position;
        cam = GameObject.Find("Main Camera").GetComponent<Camera>();
    }
 
 // Update is called once per frame
 void Update () {
        Ray ray = cam.ScreenPointToRay(Input.mousePosition);
        if (Physics.Raycast(ray, out hit) && Input.GetMouseButtonDown(0)&&hit.transform.gameObject.name == "tougu001")
        {
                mousestate = 1;
        }

        else if (Input.GetMouseButtonUp(0) && m_BLTriggerTouGu002.tougustate == 0)
        {
            mousestate = 0;
            transform.position = V3;

        }
        else if (Input.GetMouseButtonUp(0)&& m_BLTriggerTouGu002.tougustate==1)
        {
            mousestate = 0;

        }

        if (mousestate == 1&& m_BLTriggerTouGu002.tougustate!=2)
        {
            Vector3 Pos = Camera.main.WorldToScreenPoint(transform.position);
            Vector3 mousePos = new Vector3(Input.mousePosition.x, Input.mousePosition.y, Pos.z);
            transform.position = Camera.main.ScreenToWorldPoint(mousePos);

        }

    }
}

（6）tougu002 程式碼

using UnityEngine;
using System.Collections;

public class BLTriggerTouGu002 : MonoBehaviour {
    public BLtougu001 m_BLtougu001;
    public GameObject tougu;
    public float tougustate = 0f;
    private AudioSource audio_BLTriggerTouGu002;

    // Use this for initialization
    void Start () {
        tougu = GameObject.Find("tougu001");
        audio_BLTriggerTouGu002 = GetComponent<AudioSource>();
    }
 
 // Update is called once per frame

        void OnTriggerStay(Collider col)

        {
             if(tougustate!=2)
              tougustate = 1;
            if (col.tag == "touGu" && m_BLtougu001.mousestate == 0 && tougustate==1)
            {
        
              tougu.transform.position = transform.position;
                 tougustate = 2;
                transform.parent.SendMessage("CountBone", true);
            audio_BLTriggerTouGu002.Play();
            }
        }

    void OnTriggerExit(Collider col)

    {
        if (tougustate != 2)
        {
            tougustate = 0;
        }
    }

}