Perspective camera touch movement

Hi

I have a problem configuring movement of camera with touch input. I found a script on the forums that should do the job but the problem is that camera wont move over z axis. It is perspective camera so I want it just to be moved over x and z axis for purpose of kinda rts like game.

So when I move finger on the touch screen in x axis direction it works but y axis is constantly 0. I cant see where this problem occurs and why. I also need to put that y axis movement on touch screen to z axis transform of camera.

This is the code I found:

 void Update () 
  {
     if (Input.touchCount == 1) {
     Touch currentTouch = Input.GetTouch(0);
 
     if (currentTouch.phase == TouchPhase.Began) {
         this.worldStartPoint = this.getWorldPoint(currentTouch.position);
             }
 
     if (currentTouch.phase == TouchPhase.Moved) {
                 Vector2 worldDelta = this.getWorldPoint(currentTouch.position) - this.worldStartPoint;
                 Camera.main.transform.Translate( -worldDelta.x, 0, -worldDelta.y );
          }
     }
 }
 
     private Vector2 getWorldPoint(Vector2 screenPoint)
     {
         RaycastHit hit;
         Physics.Raycast(Camera.main.ScreenPointToRay(screenPoint), out hit);
         return hit.point;
      }