ThirdPersonCamera.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class ThirdPersonCamera : MonoBehaviour
{

    public Transform parentTransform;   //the transform of the player or object you want the camera to focus on
    float mouseOrgX;                   //screen x coordinate when middle mouse button is first pressed
    float mouseOrgY;                   //screen y coordinate when middle mouse button is first pressed
    public float rotSpeed;              //how fast the camera rotates around the focussed object
    public int tolerance;               
    public float zoomSpeed;             
    Vector3 targToCamNoY;               //vector from the camera to the object of focus with y=0
    float yAngle;                       
    public float yAngleTol;             //the angle in degrees that the focus object to camera vector can be from the flat plane running throw the focus object's origin
    float yCompOrg;
    bool tooHigh;
    bool tooLow;
    Vector3 playerToCamera;
    public float magAdjustment;       //controls how close a collider has to be to the back of the camera to justify turning of backwards zoom
    bool allowZoomOut;
    public int minZoomDist;
    public int maxZoomDist;
    

    // Use this for initialization
    void Start()
    {
        mouseOrgX = 0;
        mouseOrgY = 0;
        tooHigh = false;
        tooLow = false;
    }

    // Update is called once per frame
    void Update()
    {


        if (Input.GetMouseButtonDown(2))
        {
            mouseOrgX = Input.mousePosition.x;
            mouseOrgY = Input.mousePosition.y;
        }
        if (Input.GetMouseButton(2))
        {


            //left right input/movement =======================================================================================
            if (Input.mousePosition.x >= (mouseOrgX + tolerance)) //move right
            {
                gameObject.transform.Translate(Vector3.right * Time.deltaTime * rotSpeed, Space.Self);
            }
            else if (Input.mousePosition.x <= (mouseOrgX - tolerance)) //move left
            {
                gameObject.transform.Translate(Vector3.right * Time.deltaTime * -rotSpeed, Space.Self);
            }
            //========================================================================================================




            //check to see if too high or low =============================================================
            targToCamNoY = parentTransform.position - gameObject.transform.position;
            yCompOrg = targToCamNoY.y;
            targToCamNoY.y = 0;

            yAngle = Vector3.Angle(targToCamNoY, parentTransform.position - gameObject.transform.position);
            //Debug.Log("yAngle = " + yAngle + "yCompOrg = " + yCompOrg + " tooHigh = " + tooHigh + " tooLow = " + tooLow);
            if (yAngle > yAngleTol && yCompOrg < 0) //too far up
            {
                tooHigh = true;
            }
            else if (yAngle > yAngleTol && yCompOrg > 0) //too far down
            {
                tooLow = true;
            }
            //=============================================================================================




            //only listen to curtain input based on prior analysis==================================================
            if (tooHigh) //if too high only listen to downward input
            {
                if ((Input.mousePosition.y <= (mouseOrgY - tolerance))) //down
                {
                    gameObject.transform.Translate(Vector3.up * Time.deltaTime * -rotSpeed, Space.Self);
                }
            }
            else if (tooLow) // only listen to upward input
            {
                if ((Input.mousePosition.y >= (mouseOrgY + tolerance))) //up
                {
                    gameObject.transform.Translate(Vector3.up * Time.deltaTime * rotSpeed, Space.Self);
                }
            }
            else //camera is not too high or too low so listen to both up and down input
            {
                if ((Input.mousePosition.y >= (mouseOrgY + tolerance))) //up
                {
                    gameObject.transform.Translate(Vector3.up * Time.deltaTime * rotSpeed, Space.Self);
                }
                else if ((Input.mousePosition.y <= (mouseOrgY - tolerance))) //down
                {
                    gameObject.transform.Translate(Vector3.up * Time.deltaTime * -rotSpeed, Space.Self);
                }
            }
            //========================================================================================================




            //check to see if camera is no longer too high or too low =======================================
            targToCamNoY = parentTransform.position - gameObject.transform.position;
            yCompOrg = targToCamNoY.y;
            targToCamNoY.y = 0;

            yAngle = Vector3.Angle(targToCamNoY, parentTransform.position - gameObject.transform.position);
            if (yAngle <= yAngleTol - 4) //4 is arbitrary
            {
                tooHigh = false;
                tooLow = false;
            }
            //===============================================================================================


        } //end if(Input.GetMouseDown(2))


        //zoom in/out =======================================================================================
        playerToCamera = gameObject.transform.position - parentTransform.position;
        if (Input.mouseScrollDelta.y > 0 && playerToCamera.magnitude >= minZoomDist) //zoom in
        {
            gameObject.transform.Translate(Vector3.forward * Time.deltaTime * zoomSpeed, Space.Self);
        }
        else if (Input.mouseScrollDelta.y < 0 && allowZoomOut && playerToCamera.magnitude <= maxZoomDist) //zoom out
        {
            gameObject.transform.Translate(Vector3.forward * Time.deltaTime * -zoomSpeed, Space.Self);
        }
        //===================================================================================================

        gameObject.transform.rotation = Quaternion.LookRotation(parentTransform.position - gameObject.transform.position, Vector3.up);

    } //end update

    void FixedUpdate()
    {
        RaycastHit hitInfo;
        playerToCamera = gameObject.transform.position - parentTransform.position;
        
        //if a collider is blocking the line of sight of the camera snap the camera in front of the collider ...
        if (Physics.Raycast(parentTransform.position, playerToCamera, out hitInfo, playerToCamera.magnitude)) 
        {
            gameObject.transform.position = hitInfo.point;
        }

        //if a collider is too close to the backside of the camera, this prevents the user from zooming the camera out to keep the camera from jittering
        if (Physics.Raycast(parentTransform.position, playerToCamera, out hitInfo, playerToCamera.magnitude + magAdjustment))
        {
            allowZoomOut = false;
        }
        else //the is no collider that is too close to the back of the camera
        {
            allowZoomOut = true;
        }
        
    }
}