throwing a ball camera position changes

  ball.useGravity=true;
       ball.velocity=transform.TransformDirection(0,yvel,zvel);

In my scene balls start position is always next to camera. when user touched on the ball user make shot . I am using codes above for throwing ball from a certain ball and hoop place. It works fine (at least physic works fine). But My question is , when the cameras position changes in the scene, the ball's position is going to be changed as well. so what code should I use to make throw the ball to the hoop ? how to calculate? (I change cameras position with the device acceloremetre on iphone )

Thanks in advance