I want understand part of code ..!

Unity Engine
1

Hi,
Simply, I found this code in the forum (about control ball with rigidbody), and I started in studying it in order to learn unity:

var speed = 10.0;
var gravitypull = 0;



 function FixedUpdate() {
 rigidbody.AddForce (Vector3(0, gravitypull, 0));
 
 var cameraTransform = Camera.main.transform;

   // Forward vector relative to the camera along the x-z plane   
   var forward = cameraTransform.TransformDirection(Vector3.forward);
   forward.y = 0;
   forward = forward.normalized;

   // Right vector relative to the camera
   // Always orthogonal to the forward vector
   var right = Vector3(forward.z, 0, -forward.x);

 
 if (Input.GetKey ("w")) {
   rigidbody.AddForce(forward * speed * Time.deltaTime);
   }

if (Input.GetKey("s")) {
   rigidbody.AddForce(forward * -speed * Time.deltaTime);
   }
   
if (Input.GetKey ("d")) {
rigidbody.AddForce(right * speed * Time.deltaTime);
}

if (Input.GetKey ("a")) {
rigidbody.AddForce(right * -speed * Time.deltaTime);
}

 }

I understand most of the code, but the following part I do not understand how important, and what is the relationship move the ball with the camera:

var cameraTransform = Camera.main.transform;

   // Forward vector relative to the camera along the x-z plane   
   var forward = cameraTransform.TransformDirection(Vector3.forward);
   forward.y = 0;
   forward = forward.normalized;

   // Right vector relative to the camera
   // Always orthogonal to the forward vector
   var right = Vector3(forward.z, 0, -forward.x);
2

Those lines basically just set up the variables forward and right, which are used in the later keyPress events to stear the ball.

The whole bit about the camera basically makes it so the ball rolls forward, with forward being defined by the direction/vector the camera is facing.