title: Dynamically adding 3d objects to a scene in Unity3d
body: <p>I am working on an Unity3d project in which I want to dynamically add 3d objects to the scene, at the same position, orientation, upon a keyPress. For doing so, I imported these objects and made a prefab for all of these.. I am using the following script to do so.. bt it doesn't do the needfull.. The new object gets instantiated and gets added to the scene but the old objects don't get destroyed. And also ,the position of the new objects is not always the same. The scene consists of a Cube initially. After I press '1' ,'2' etc .. I want a new Object to replace the 1 being displayed (at the same position).</p>
  
  <p>script :</p>
  
  <pre><code>var myCar : GameObject;
  var Cube : GameObject;
  var Globe: GameObject;
  var Clock : GameObject;
  var Pistol : GameObject;
  var LCD : GameObject;
  var prev : int;
  var temp: GameObject; 
  function Start ()
  {
      prev =0;
      temp=null;
  
  }
  
  function Update () 
  {
      if(prev==0)
          temp=Cube;
      else if(prev==1)
          temp=myCar;
      else if(prev==2)
          temp=Globe;
      else if(prev==3)
          temp=Pistol;
      else if(prev==4)
          temp=Clock;
      else if(prev==5)
          temp=LCD;       
  
      if(Input.GetKey(KeyCode.Alpha1 || KeyCode.Keypad1))
      {
          if(prev!=1)
          {
              Instantiate(myCar,temp.transform.position ,temp.transform.rotation);
              myCar.transform.localScale = Vector3(0.06,0.06,0.06);
              Destroy(temp);
              prev=1;
          }     
      }
      else if(Input.GetKey(KeyCode.Alpha2 || KeyCode.Keypad2))
      {
       if(prev!=2)
       {
          Instantiate(Globe,temp.transform.position ,temp.transform.rotation);
          Globe.transform.localScale = Vector3(0.04,0.04,0.04);
          Destroy(temp);
          prev=2;
       }
  
      }
      else if(Input.GetKey(KeyCode.Alpha3 || KeyCode.Keypad3))
      {
       if(prev!=3)
       {
          Instantiate(Pistol,temp.transform.position ,temp.transform.rotation);
          Pistol.transform.localScale = Vector3(0.03,0.03,0.03);
          Destroy(temp);
          prev =3;
       }
      }
      else if(Input.GetKey(KeyCode.Alpha4 || KeyCode.Keypad4))
      {
       if(prev!=4)
       {
            Instantiate(Clock,temp.transform.position ,temp.transform.rotation);
            Clock.transform.localScale = Vector3(0.08,0.08,0.08);
              Destroy(temp);
              prev=4;
       }
  
      }
      else if(Input.GetKey(KeyCode.Alpha5 || KeyCode.Keypad5))
      {
       if(prev!=5)
       {
          Instantiate(LCD,temp.transform.position ,temp.transform.rotation);
          LCD.transform.localScale = Vector3(0.04,0.04,0.04);
          Destroy(temp);
          prev=5;
       }
      }
  }
  </code></pre>