Unity camera tilt

Question

I'm programming a camera for an RTS and I'm stuck on tilting the camera up and down.

I want the camera to tilt between 20 and 70 degrees using the Z and X keys. This is my code:

using UnityEngine;
using System.Collections;

public class CameraController : MonoBehaviour {

    //Variables to alter or track in Unity
    public float scrollSpeed;
    public float increasedScroll;
    public float scrollEdge;
    public float panSpeed;
    public float increasedPan;
    public float rotateSpeed;
    public float currentZoom;
    public float zoomSpeed;
    public float zoomRotation;
    public Vector2 zoomRange;
    public float tiltAngle;
    public Vector2 tiltAngleRange;

    //Variables for use in script
    private Vector3 initialPosition;
    private Quaternion initialRotation;
    private Vector3 mouse;

    //
    void Start()
    {
        initialPosition = transform.position;
        initialRotation = transform.rotation;
    }

    //Each frame
    void Update()
    {
        //BASIC CAMERA MOVEMENT (panning)

        //Check for shift key input and change speed accordingly
        shiftSpeed(increasedPan, increasedScroll);

        //Pan with middle mouse
        mouse = Input.mousePosition;
        if (Input.GetKey("mouse 2"))
        {
            panMove(Vector3.right, mouse.x, Screen.width);
            panMove(Vector3.forward, mouse.y, Screen.height);
        }
        //Pan with WASD keys or edge of screen
        else
        {
            if(Input.GetKey("d") || mouse.x >= Screen.width * (1 - scrollEdge))
            {
                moveCamera(Vector3.right, scrollSpeed);
            }
            else if (Input.GetKey("a") || mouse.x <= Screen.width * scrollEdge)
            {
                moveCamera(Vector3.right, -scrollSpeed);
            }
            if (Input.GetKey("w") || mouse.y >= Screen.height * (1 - scrollEdge))
            {
                moveCamera(Vector3.forward, scrollSpeed);
            }
            else if (Input.GetKey("s") || mouse.y <= Screen.width * scrollEdge)
            {
                moveCamera(Vector3.forward, -scrollSpeed);
            }
        }

        //Camera zoom with scrl wheel (up and down)
        currentZoom -= Input.GetAxis("Mouse ScrollWheel") * Time.deltaTime * 1000 * zoomSpeed;
        currentZoom = Mathf.Clamp(currentZoom, zoomRange.x, zoomRange.y);
        transform.position = new Vector3(transform.position.x, transform.position.y - (transform.position.y - (initialPosition.y + currentZoom)) * 0.1f, transform.position.z);

        //Camera tilt with ZX keys
        if (Input.GetKey("z"))
        {
            tiltCamera(tiltAngle);
        }
        else if (Input.GetKey("x"))
        {
            tiltCamera(-tiltAngle);
        }

    }

    //Occurs after update
    void LateUpdate()
    {
        //Remove shifted spped
        shiftSpeed(-increasedPan, -increasedScroll);
    }

    void shiftSpeed(float panChange, float scrollChange)
    {
        if (Input.GetKey(KeyCode.LeftShift))
        {
            panSpeed += panChange;
            scrollSpeed += scrollChange;
        }
    }

    void panMove(Vector3 panDirection, float inputDirection, int screenAxis)
    {
        moveCamera(panDirection, panSpeed * ((inputDirection - screenAxis * 0.5f) / (screenAxis * 0.5f)));
    }

    void moveCamera(Vector3 direction, float scrlOrPanSpeed)
    {
        transform.Translate(direction * Time.deltaTime * scrlOrPanSpeed, Space.World);
    }

    void tiltCamera(float angle)
    {
        angle = angle + initialRotation.eulerAngles.x;
        Quaternion newRotation = Quaternion.AngleAxis(angle, Vector3.left);
        transform.rotation = Quaternion.Slerp(transform.rotation, newRotation, 1f);
    }
}

At the moment it just tilts up or down by 1 degree from the starting rotation when I press Z and X.

Answer 1

Well, to achieve your requirement, I have another work around, place these lines of code in very same script.

...

public float _cameraRotationSpeed = 0.1f;

...
void Update ()
    {
        ...
        ...

        if (Input.GetKey ("z")) {
            tiltCamera (true); // Replace parameter with bool
        } else if (Input.GetKey ("x")) {
            tiltCamera (false); // Replace parameter with bool
        }

        ...
        ...
    }

// Replace your tilt camera method by

void tiltCamera (bool rotateRight)
    {
        // Y represents rotation around Y-axis and will rotate in x-z axes. You can modify it.

        float angle = transform.eulerAngles.y;
        if (rotateRight)
            angle += _cameraRotationSpeed;
        else
            angle -= _cameraRotationSpeed;
        angle = Mathf.Clamp (angle, 20, 70);

        // Whatever reference you got in angle change exactly that same axis. For now Y rotation is being changed.
        transform.eulerAngles = new Vector3 (transform.eulerAngles.x, angle, transform.eulerAngles.z);
    }
...