title: Unity - Phyics.Raycast returns false
body: <p>I create an emtpy game object and attach .cs file. I try to load a prefab(.obj file) on mouse click position. My code is : </p>
  
  <pre><code>    Ray ray;
      RaycastHit hit;
      public GameObject prefab;
  
      void Start()
      {
      }
  
      // Update is called once per frame
      void Update()
      {
  
          if (Input.GetMouseButtonDown(0))
          {
              ray=Camera.main.ScreenPointToRay(Input.mousePosition);
  
              if (Physics.Raycast(ray, out hit))
              {
                  GameObject obj = Instantiate(prefab, new Vector3(hit.point.x, hit.point.y, hit.point.z), Quaternion.identity) as GameObject;
  
              }
              else
              {
                  Debug.Log("Physics.Raycast returns false");
              }
      }
  </code></pre>
  
  <p>Raycast returns false everytime.</p>