Unity: rotating object around Z axis with Lerp/Slerp - rotation

Question

Im trying to rotate my player to face where I last clicked. I've acutally manged to do this, but now I want to see the player rotate at a set speed instead of the sprite just changing rotation instantly.
Ive tried several methods I've found online, but none of them work for me. Here's what I have
void Update()
{
if (Input.GetMouseButtonDown (0))
{
Vector3 diff = Camera.main.ScreenToWorldPoint(Input.mousePosition) - transform.position;
diff.Normalize();
float rot_z = Mathf.Atan2(diff.y, diff.x) * Mathf.Rad2Deg;
transform.rotation= Quaternion.Euler(0f, 0f, rot_z - 90);
Instantiate(ProjectilePrefab, transform.position, transform.rotation);
}
}
The code above works fine, but it shows no movement. I have tried to do this but the position is wrong and the rotation is instant as well:
Vector3 diff = Camera.main.ScreenToWorldPoint(Input.mousePosition) - transform.position;
var newRotation = Quaternion.LookRotation(diff);
newRotation.y = 0.0f;
newRotation.x = 0.0f;
transform.rotation = Quaternion.Slerp(transform.rotation, newRotation, Time.deltaTime * 30);
ANy ideas?

Answer 1

Two problems here. First, the Slerp function is only called once after the user pressed the mouse button. You have to move it outside the if part or use a coroutine. Second, Slerp expects a float from 0 to 1 to indicate the progress and not time or deltaTime. The official examples covering the lerp functions are just bad, because using the time value would work only during the first second the game is running.
You need something like this
if (Input.GetMouseButtonDown (0)) {
// your other stuff here
float starTime = Time.time;
}
float t = Time.time - startTime;
transform.rotation = Quaternion.Slerp(transform.rotation, newRotation, t);
The rotation would finish after one second. If you want it faster or slower just multiply t with a factor.

Answer 2

I found the answer. This is how I made it work
if (Input.GetMouseButtonDown (0)) {
target = Camera.main.ScreenToWorldPoint (Input.mousePosition);
rotateToTarget = true;
print ("NEW TARGET: " + target);
}
if (rotateToTarget == true && target != null) {
print ("Rotating towards target");
targetRotation = Quaternion.LookRotation (transform.position - target.normalized, Vector3.forward);
targetRotation.x = 0.0f;//Set to zero because we only care about z axis
targetRotation.y = 0.0f;
player.transform.rotation = Quaternion.Slerp (transform.rotation, targetRotation, Time.deltaTime * rotationSpeed);
if (Mathf.Abs (player.transform.rotation.eulerAngles.z - targetRotation.eulerAngles.z) < 1) {
rotateToTarget = false;
travelToTarget = true;
player.transform.rotation = targetRotation;
print ("ROTATION IS DONE!");
}
}