I can't make a smooth rotation angle when pressing the button - unity3d

Question

public float tilt =-5f;
public float horizontal;
public float vertical;
Rigidbody player;
void Start()
{
player = GetComponent<Rigidbody>();
}
void Update()
{
player.velocity = new Vector3(horizontal, vertical, 7f);
var clamX = Mathf.Clamp(player.position.x, xmin, xmax);
var clamY = Mathf.Clamp(player.position.y, ymin, ymax);
player.position = new Vector3(clamX, clamY, player.position.z);
player.rotation = Quaternion.Euler(vertical*tilt,0, horizontal * tilt);
}
//turn on the left
public void Onleft()
{
horizontal = -7f;
}
//turn on the right
public void OnRigth()
{
horizontal = 7f;
}
public void Up()
{
horizontal = 0f;
}
// I added an event trigger on my buttons, and ofcourse added some function to this event: OnLeft(),OnRight(), but after added buttons the angle of the ship's turn became very fast, how to fix it so that the angle of rotation of the ship, when pressing the button to the left or right, was little bit smooth?

Answer 1

Well, there is a difference between smooth and slower.
To achieve an slower rotation, simply multiply your rotation value for another value.
rotationValue = 10;
speed = 1/2;
//newRotationValue
rotationValue *= speed; //5;
But if you want to smooth your movement transitions/rotations, I highly recommend you to use Lerp, more concretly as you are using rotations, Quaternion.Lerp .
Lerp will make your rotations to linearly interpolates between two points (your start rotation and your final rotation) and normalize the result, so it will seem more "smooth".