public class ObjectDragger : MonoBehaviour 
{
 
	private Vector3 screenPoint;
	private Vector3 offset;

	bool dragged = false;

	private Vector3 newPosition;//賦值給物體的座標位置
	private Rigidbody body;

	void Awake(){
        //獲取自身重力
		body = gameObject.GetComponent<Rigidbody>();
        //獲取自身初始座標
		newPosition = transform.position;
	}
	 
	 void OnMouseDown()
	 {
        //按下滑鼠時獲取自身當前座標的螢幕座標
	     screenPoint = Camera.main.WorldToScreenPoint(gameObject.transform.position);
        //按下滑鼠時記錄物體的世界座標，和滑鼠世界座標的向量偏移
        offset = gameObject.transform.position - 
            Camera.main.ScreenToWorldPoint(new Vector3(Input.mousePosition.x, Input.mousePosition.y, screenPoint.z));
	 }
	 
	 void OnMouseDrag()
	 {
        //按下拖動滑鼠時
		dragged = true;
        Debug.Log("按下拖動滑鼠時");
	 }

	 void FixedUpdate(){
		if (dragged){

			dragged = false;
            //當前滑鼠的螢幕座標
			Vector3 curScreenPoint = new Vector3(Input.mousePosition.x, Input.mousePosition.y, screenPoint.z);
            //保持物體與滑鼠的位置偏移量
            newPosition = Camera.main.ScreenToWorldPoint(curScreenPoint) + offset;

			if (body != null)
				body.velocity = (newPosition - transform.position) / Time.deltaTime;
            Debug.Log(body.velocity);
		}
	 }

	 void LateUpdate(){
        //移動程式碼
		transform.position = newPosition;
	 }
 
 }