smoothly recenter view over time

Question

I'm currently using the Google Cardboard SDK for Unity to build a fighter pilot simulator. What I'm currently trying to do is recenter the view(CardboardHead) smoothly over time when the user looks away from the screen. This is because I want to put HUD elements out of the main central view that can be quickly seen with a "head jerk". I don't want to let the camera be free from constraints because I feel piloting is much better when the view is fixed and doesn't wobble about with every slight movement of the player's head. The Head already has a horizontal constraint that does not allow any later movement, but now I want to put a semi-constraint on the vertical axis so that the player can quickly look up or down to see something like i.e. a fuel economy indicator and then have the view quickly "follow his gaze" and recenter itself.

I noticed that the Cardboard plugin already does this type of constraint on the Head roll input when playing "in editor" and works as follows: When you press and hold Ctrl and move the mouse left/right the view rolls left/right. Upon release of Ctrl the view smoothly rolls back to 0. This is the code in the Cardboard script:

bool rolled = false;
if (Input.GetKey(KeyCode.LeftControl) || Input.GetKey(KeyCode.RightControl)) {
      rolled = true;
      mouseZ += Input.GetAxis("Mouse X") * 5;
      mouseZ = Mathf.Clamp(mouseZ, -80, 80);
    }
    if (!rolled && autoUntiltHead) {
      // People don't usually leave their heads tilted to one side for long.
      mouseZ = Mathf.Lerp(mouseZ, 0, Time.deltaTime / (Time.deltaTime + 0.1f));
    }
    var rot = Quaternion.Euler(mouseY, mouseX, mouseZ);
    var neck = (rot * neckOffset - neckOffset.y * Vector3.up) * NeckModelScale;
    headView = Matrix4x4.TRS(neck, rot, Vector3.one);
  }

How could I implement this for vertical rotation of the Head?

In the Update method of the script that controls the Head it simply does transform.localRotation = Cardboard.SDK.HeadRotation;

This is what I've tried but it doesn't really do anything except some jerky movements:

transform.Rotate(new Vector3(Mathf.Lerp(rot.eulerAngles.x, 0, Time.deltaTime / (Time.deltaTime + 0.1f)),0,0));

(I put this in the same Update function for the Head after the above line)

Any ideas??

Answer 1

Look at using Unity's Quaternion.RotateTowards and smooth the rotation per frame with something like the following:

    void Update()
    {
        float speed = 1f; // can adjust this to move faster or slower
        float step = speed * Time.smoothDeltaTime;
        Quaternion targetRotation = Quaternion.identity;
        transform.rotation = Quaternion.RotateTowards(transform.rotation, targetRotation, step);
    }