Testing script for rotate a 3d object in Unity3D

RotateHandler.cs

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

public class GestureHandler : MonoBehaviour {

	public float rotationSpeed = 8;

  public Camera cam;
	
	// Use this for initialization
	float rotSpeed = 20;

	public float moveSpeed = 10f;
    public float turnSpeed = 50f;

    void OnMouseDrag()
    {
        float rotX = Input.GetAxis("Mouse X")*rotSpeed*Mathf.Deg2Rad;
        float rotY = Input.GetAxis("Mouse Y")*rotSpeed*Mathf.Deg2Rad;

        // giro somente pelas laterais
        // float rotX = Input.GetAxis("Mouse X")*rotSpeed*Mathf.Deg2Rad;
        // transform.RotateAround(Vector3.up, -rotX);

        transform.RotateAround(transform.up, -rotX);
        transform.RotateAround(Vector3.right, rotY);
		// transform.Rotate(Vector3.right *rotSpeed * Time.deltaTime);
        // transform.Rotate(0,5,0, Space.World);
    }

	void Start () {
		
	}
	
	// Update is called once per frame
	void Update () {
		// RotateObject();

		// if(Input.GetKey(KeyCode.UpArrow))
        //     transform.Translate(Vector3.forward * moveSpeed * Time.deltaTime);
        
        // if(Input.GetKey(KeyCode.DownArrow))
        //     transform.Translate(-Vector3.forward * moveSpeed * Time.deltaTime);
        
        // if(Input.GetKey(KeyCode.LeftArrow))
        //     transform.Rotate(Vector3.up, -turnSpeed * Time.deltaTime);
        
        // if(Input.GetKey(KeyCode.RightArrow))
        //     transform.Rotate(Vector3.up, turnSpeed * Time.deltaTime);
	}
	
    void RotateObject()
    {
          //Get mouse position
        Vector3 mousePos = Input.mousePosition;
         
        //Adjust mouse z position
        mousePos.z = cam.transform.position.y - transform.position.y;   
 
        //Get a world position for the mouse
        Vector3 mouseWorldPos = cam.ScreenToWorldPoint(mousePos);   
 
         //Get the angle to rotate and rotate
        float angle = -Mathf.Atan2(transform.position.z - mouseWorldPos.z, transform.position.x - mouseWorldPos.x) * Mathf.Rad2Deg;
        transform.rotation = Quaternion.Slerp(transform.rotation, Quaternion.Euler(0, angle, 0), rotationSpeed * Time.deltaTime);
    }
}