TP_Camera.cs

using UnityEngine;
using System.Collections;

public class TP_Camera : MonoBehaviour
{
    public static TP_Camera Instance;

    public Transform TargetLookAt;

    public float Distance = 5f;
    public float DistanceMin = 3f;
    public float DistanceMax = 10f;
    public float DistanceSmooth = 0.05f;
    public float X_MouseSensitivity = 5f;
    public float Y_MouseSensitivity = 5f;
    public float MouseWheelSensitivity = 5f;
    public float X_Smooth = 0.05f;
    public float Y_Smooth = 0.1f;
    public float Y_MinLimit = -40f;
    public float Y_MaxLimit = 80f;


    private float mouseX = 0f;
    private float mouseY = 0f;
    private float velX = 0f;
    private float velY = 0f;
    private float velZ = 0f;
    private float velDistance = 0f;
    private float startDistance = 0f;
    private Vector3 position = Vector3.zero;
    private Vector3 desiredPosition = Vector3.zero;
    private float desiredDistance = 0f;


    void Awake()
    {
        Instance = this;
    }

    // Use this for initialization
    void Start ()
    {
        Distance = Mathf.Clamp (Distance, DistanceMin, DistanceMax);
        startDistance = Distance;
        Reset ();


    }

    void LateUpdate ()
    {
        if (TargetLookAt == null)
            return;

        HandlePlayerInput ();
        CalculateDesiredPosition ();
        UpdatePosition ();
    }

    void HandlePlayerInput()
    {
        var deadZone = 0.1f;


        // If right mouse button is held down and is true
        if (Input.GetMouseButton(1))
        {
            // The RMB is down, get mouse axis input
            mouseX += Input.GetAxis("Mouse X") * X_MouseSensitivity;
            mouseY -= Input.GetAxis("Mouse Y") * Y_MouseSensitivity;
        }

        // This is where we will limit mouseY

        mouseY = Helper.ClampAngle (mouseY, Y_MinLimit, Y_MaxLimit);

        if (Input.GetAxis("Mouse ScrollWheel") < -deadZone || Input.GetAxis("Mouse ScrollWheel") > -deadZone )
        {
            desiredDistance = Mathf.Clamp(Distance - Input.GetAxis("Mouse ScrollWheel") * MouseWheelSensitivity,
                                          DistanceMin, DistanceMax);

        }
    }

    void CalculateDesiredPosition()
    {
        // Evaluluate distance
        Distance = Mathf.SmoothDamp (Distance, desiredDistance, ref velDistance, DistanceSmooth);

        // Calculate desired position
        desiredPosition = CalculatePosition (mouseY, mouseX, Distance);


    }

    Vector3 CalculatePosition(float rotationX, float rotationY, float distance)
    {
        Vector3 direction = new Vector3 (0, 0, -distance);
        Quaternion rotation = Quaternion.Euler (rotationX, rotationY, 0);
        return TargetLookAt.position + rotation * direction;
    }

    void UpdatePosition()
    {
        var posX = Mathf.SmoothDamp (position.x, desiredPosition.x, ref velX, X_Smooth);
        var posY = Mathf.SmoothDamp (position.y, desiredPosition.y, ref velY, Y_Smooth);
        var posZ = Mathf.SmoothDamp (position.z, desiredPosition.z, ref velZ, X_Smooth);
        position = new Vector3 (posX, posY, posZ);

        transform.position = position;

        transform.LookAt (TargetLookAt);
    }

    public void Reset ()
    {
        mouseX = 0;
        mouseY = 10;
        Distance = startDistance;
        desiredDistance = Distance;


    }

    public static void UseExistingOrCreateNewMainCamera()
    {
        GameObject tempCamera;
        GameObject targetLookAt;
        TP_Camera myCamera;

        if (Camera.mainCamera != null)
        {
            tempCamera = Camera.mainCamera.gameObject;
        }
        else
        {
            tempCamera = new GameObject("Main Camera");
            tempCamera.AddComponent("Camera");
            tempCamera.tag = "MainCamera";
        }

        tempCamera.AddComponent ("TP_Camera");
        myCamera = tempCamera.GetComponent ("TP_Camera") as TP_Camera;

        targetLookAt = GameObject.Find("tagetLookAt") as GameObject;

        if (targetLookAt == null)
        {
            targetLookAt = new GameObject("targetLookAt");
            targetLookAt.transform.position = Vector3.zero;
        }

        myCamera.TargetLookAt = targetLookAt.transform;

    }
}