How do I make a combination of orbit and TPS camera like in gta

I have this camera orbit script that doesn't clip through walls. how do i make it like gta?

using UnityEngine; using System.Collections;

public class OrbitCamera : MonoBehaviour { / These variables are what tell the camera how its going to function by setting the viewing target, collision layers, and other properties such as distance and viewing angles / public Transform viewTarget; public LayerMask collisionLayers; public float distance = 6.0f; public float distanceSpeed = 150.0f; public float collisionOffset = 0.3f; public float minDistance = 4.0f; public float maxDistance = 12.0f; public float height = 1.5f; public float horizontalRotationSpeed = 250.0f; public float verticalRotationSpeed = 150.0f; public float rotationDampening = 0.75f; public float minVerticalAngle = -60.0f; public float maxVerticalAngle = 60.0f; public bool useRMBToAim = false;

 /* These variables are meant to store values given by the script and
   * not the user */
 private float h, v, newDistance, smoothDistance;
 private Vector3 newPosition;
 private Quaternion newRotation, smoothRotation;
 private Transform cameraTransform;

 /* This is where we initialize our script */
 void Start () {
     Initialize ();
 }

 /* This is where we set our private variables, check for null errors,
   * and anything else that needs to be called once during startup */
 void Initialize () {
     h = this.transform.eulerAngles.x;
     v = this.transform.eulerAngles.y;

     cameraTransform = this.transform;
     smoothDistance = distance;

     NullErrorCheck ();
 }

 /* We check for null errors or warnings and notify the user to fix them */
 void NullErrorCheck () {
     if (!viewTarget) {
         Debug.LogError("Please make sure to assign a view target!");
         Debug.Break ();
     }
     if (collisionLayers == 0) {
         Debug.LogWarning("Make sure to set the collision layers to the layers the camera should collide with!");
     }
 }

 /* This is where we do all our camera updates. This is where the camera
   * gets all of its functionality. From setting the position and rotation,
   * to adjusting the camera to avoid geometry clipping */
 void LateUpdate () {
     if (!viewTarget)
         return;

     /* We check for right mouse button functionality, set the rotation
       * angles, and lock the mouse cursor */
     if (!useRMBToAim) {
         /* Check to make sure the game isn't paused and lock the mouse cursor*/
         if (Time.timeScale > 0.0f)
             Screen.lockCursor = true;

         h += Input.GetAxis ("Mouse X") * horizontalRotationSpeed * Time.deltaTime;
         v -= Input.GetAxis ("Mouse Y") * verticalRotationSpeed * Time.deltaTime;

         h = ClampAngle (h, -360.0f, 360.0f);
         v = ClampAngle (v, minVerticalAngle, maxVerticalAngle);

         newRotation = Quaternion.Euler(v, h, 0.0f);
     } else {
         if(Input.GetMouseButton(1)) {
             /* Check to make sure the game isn't paused and lock the mouse cursor */
             if (Time.timeScale > 0.0f)
                 Screen.lockCursor = true;

             h += Input.GetAxis ("Mouse X") * horizontalRotationSpeed * Time.deltaTime;
             v -= Input.GetAxis ("Mouse Y") * verticalRotationSpeed * Time.deltaTime;

             h = ClampAngle (h, -360.0f, 360.0f);
             v = ClampAngle (v, minVerticalAngle, maxVerticalAngle);

             newRotation = Quaternion.Euler(v, h, 0.0f);
         } else {
             Screen.lockCursor = false;
         }
     }

     /* We set the distance by moving the mouse wheel and use a custom
       * growth function as the time value for linear interpolation */
     distance = Mathf.Clamp (distance - Input.GetAxis ("Mouse ScrollWheel") * 10, minDistance, maxDistance);
     smoothDistance = Mathf.Lerp (smoothDistance, distance, TimeSignature(distanceSpeed));

     /*We give the rotation some smoothing for a nicer effect */
     smoothRotation = Quaternion.Slerp (smoothRotation, newRotation, TimeSignature((1 / rotationDampening) * 100.0f));

     newPosition = viewTarget.position;
     newPosition += smoothRotation * new Vector3(0.0f, height, -smoothDistance);

     /* Calls the function to adjust the camera position to avoid clipping */
     CheckSphere ();

     smoothRotation.eulerAngles = new Vector3 (smoothRotation.eulerAngles.x, smoothRotation.eulerAngles.y, 0.0f);

     cameraTransform.position = newPosition;
     cameraTransform.rotation = smoothRotation;
 }

 /* This is where the camera checks for a collsion hit within a specified radius,
   * and then moves the camera above the location it hit with an offset value */
 void CheckSphere () {
     /* Add height to our spherecast origin */
     Vector3 tmpVect = viewTarget.position;
     tmpVect.y += height;

     RaycastHit hit;

     /* Get the direction from the camera position to the origin */
     Vector3 dir = (newPosition - tmpVect).normalized;

     /* Check a radius for collision hits and then set the new position for
       * the camera */
     if(Physics.SphereCast(tmpVect, 0.3f, dir, out hit, distance, collisionLayers)) {
         newPosition = hit.point + (hit.normal * collisionOffset);
     }
 }

 /* Keeps the angles values within their specificed minimum and maximum
   * inputs while at the same time putting the values back to 0 if they 
   * go outside of the 360 degree range */
 private float ClampAngle (float angle, float min, float max) {
     if(angle < -360)
         angle += 360;

     if(angle > 360) 
         angle -= 360;

     return Mathf.Clamp (angle, min, max);
 }

 /* This is our custom logistic growth time signature with speed as input */
 private float TimeSignature(float speed) {
     return 1.0f / (1.0f + 80.0f * Mathf.Exp(-speed * 0.02f));
 }

}