Raycast moves away from object when object is rotated.

i have a game object with a script attached. I am casting a series of rays around the object. The problem is that when i move the object away from world origin and rotate it this causes the ray direction to move in the opposite direction. The problem doesn't occur if I move the object or rotate the object. It only happens when i do both. Here's the code. Thanks in advance.

      for (int i = 0; i < NumOfRays; i++) {
         x = Mathf.Sin (angle);
         z = Mathf.Cos (angle);
         angle += 2 * Mathf.PI / NumOfRays;

         Vector3 dir = transform.TransformDirection( new Vector3 (transform.position.x + x, 0, transform.position.z + z));
         Debug.DrawLine (transform.position, dir, Color.red);

         if (Input.GetKeyDown(KeyCode.UpArrow))
         rb.AddForce (Vector3.forward);
     }
     angle = 0;
 }