鼠标拖拽

1.把这段脚本拖给想要拖拽的物体，然后加上碰撞盒就可以了。

    private Vector3 _vec3TargetScreenSpace;// 目标物体的屏幕空间坐标  
    private Vector3 _vec3TargetWorldSpace;// 目标物体的世界空间坐标  
    private Transform _trans;// 目标物体的空间变换组件  
    private Vector3 _vec3MouseScreenSpace;// 鼠标的屏幕空间坐标  
    private Vector3 _vec3Offset;// 偏移  

    void Awake()
    {
        _trans = transform; 
    }

    IEnumerator OnMouseDown()
    {
        // 把目标物体的世界空间坐标转换到它自身的屏幕空间坐标   
        _vec3TargetScreenSpace = Camera.main.WorldToScreenPoint(_trans.position);

        // 存储鼠标的屏幕空间坐标（Z值使用目标物体的屏幕空间坐标）   
        _vec3MouseScreenSpace = new Vector3(Input.mousePosition.x, Input.mousePosition.y, _vec3TargetScreenSpace.z);

        // 计算目标物体与鼠标物体在世界空间中的偏移量   
        _vec3Offset = _trans.position - Camera.main.ScreenToWorldPoint(_vec3MouseScreenSpace);

        // 鼠标左键按下   

        while (Input.GetMouseButton(0))
        {
            // 存储鼠标的屏幕空间坐标（Z值使用目标物体的屏幕空间坐标）  
            _vec3MouseScreenSpace = new Vector3(Input.mousePosition.x, Input.mousePosition.y, _vec3TargetScreenSpace.z);

            // 把鼠标的屏幕空间坐标转换到世界空间坐标（Z值使用目标物体的屏幕空间坐标），加上偏移量，以此作为目标物体的世界空间坐标  
            _vec3TargetWorldSpace = Camera.main.ScreenToWorldPoint(_vec3MouseScreenSpace) + _vec3Offset;

            // 更新目标物体的世界空间坐标   
            _trans.position = _vec3TargetWorldSpace;

            // 等待固定更新   
            yield return new WaitForFixedUpdate();
        }
    }  
}

2.实现用鼠标拖拽鼠标  鼠标进入物体改变物体颜色

    public Texture2D[] pic = new Texture2D[4];
    private Color c;
    private Texture origPic;
    private int index;

    private Vector3 screenPoint;
    private Vector3 scanPos;
    private Vector3 offset;
    private Vector3 origPos;

    static public bool bDrag;
    // Use this for initialization    
    void Start()
    {
        c = GetComponent<Renderer>().material.color;
        origPic = GetComponent<Renderer>().material.mainTexture;
        //pic = new Texture2D[4];    
        index = 0;
        scanPos = this.transform.position;
        origPos = scanPos;
        bDrag = false;
    }

    // Update is called once per frame    
    void Update()
    {

    }
    void OnMouseDown()
    {
        print("Mouse down");
        GetComponent<Renderer>().material.color = c;
        GetComponent<Renderer>().material.mainTexture = pic[index];
        index++;
        if (index == 3)
            index = 0;

        /////    
        screenPoint = Camera.main.WorldToScreenPoint(scanPos);
        offset = scanPos - Camera.main.ScreenToWorldPoint(new Vector3(Input.mousePosition.x, Input.mousePosition.y, screenPoint.z));
        Vector3 curScreenPoint = new Vector3(Input.mousePosition.x, Input.mousePosition.y, screenPoint.z);
        Vector3 curPosition = Camera.main.ScreenToWorldPoint(curScreenPoint) + offset;
        //print(curPosition);    
        transform.position = curPosition;
    }
    void OnMouseEnter()
    {
        print("Mouse enter");
        index = 0;
        GetComponent<Renderer>().material.color = Color.red;
    }
    void OnMouseExit()
    {
        print("Mouse exit");
        GetComponent<Renderer>().material.color = c;
        GetComponent<Renderer>().material.mainTexture = origPic;
    }

    void OnMouseDrag()
    {
        bDrag = true;
        Vector3 curScreenPoint = new Vector3(Input.mousePosition.x, Input.mousePosition.y, screenPoint.z);
        Vector3 curPosition = Camera.main.ScreenToWorldPoint(curScreenPoint) + offset;
        transform.position = curPosition;
        print("curPosition" + curPosition);
    }

    void OnMouseUp()
    {
        print("mouse up");
        //transform.TransformPoint(origPos);    
        bDrag = false;
        transform.position = origPos;
    }