unity3d：模型跟随鼠标运动

Vector3 screenPos = Camera.main.WorldToScreenPoint(transform.position); // 目的获取z，在Start方法  
Vector3 mousePos = Input.mousePosition;  
mousePos.z = screenPos.z; // 这个很关键  
Vector3 worldPos = Camera.main.ScreenToWorldPoint(mousePos);  
this.transform.position = worldPos;   

模型跟随鼠标运动