Unity3d position the model, rotate, drag and zoom around the model to obtain the center point of the model

This script hangs on  Camera（ The camera ） On .

Locating a model is used to locate the model in front of it after finding it , Then it has the following operation functions ;

Similar to the operation in editor mode , Use as browsing model , rotate 、 Dragging and scaling are both operational Camera（ The camera ） Displacement ;

Highlight used HighlightingSystem plug-in unit ;

The center point is not of the model transform.position, It's the center of the model , Because some models position Not the center of the model , So this method is needed .

using HighlightingSystem;
using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.UI;

public class Test01 : MonoBehaviour {

    public Transform obj;
    float maxX, maxY, maxNum;
    //float minx, minY, minZ;
    private Vector3 centerPoint;

    #region  Browse model manipulation properties 
    /// <summary>
    ///  Zoom distance 
    /// </summary>
    public float ZoomSpeed = 30;
    /// <summary>
    ///  Drag speed 
    /// </summary>
	public float MovingSpeed = 0.5f;
    /// <summary>
    ///  Angle of view swing speed 
    /// </summary>
	public float RotateSpeed = 1;
    /// <summary>
    ///  Camera rotation speed 
    /// </summary>
    public float distance = 30;

    Quaternion rotation;
    Vector3 position;
    float delta_x, delta_y, delta_z;
    float delta_rotation_x, delta_rotation_y; 
    #endregion

   

    void Start () {
        // Calculate the position point directly in front of the model 
        Mesh mesh = obj.GetComponent<MeshFilter>().mesh;
        Vector3[] vertices = mesh.vertices;
        //minZ = obj.position.z;
        // Calculate the maximum vertex , Judge the longest or widest of the model , Used to calculate the distance from the positioning point to the model 
        foreach (Vector3 item in vertices)
        {
            if (item.x > maxX)
            {
                maxX = item.x;
            }
            if (item.y > maxY)
            {
                maxY = item.y;
            }
        }

        centerPoint = GetCenter(obj.gameObject);

        // Get the longest end of the model as the calculated viewpoint distance 
        if (maxX > maxY)
        {
            maxNum = maxX;
        }
        else
        {
            maxNum = maxY;
        }
        if (maxNum < 5) maxNum = 5;
        // Obtain the viewpoint directly in front of the model 
        Camera.main.transform.position = new Vector3(centerPoint.x, centerPoint.y, centerPoint.z - maxNum);
        
//================================================
// Method 2 ： If obj The object is static , In this way 
        //Renderer[] mrs = obj.GetComponentsInChildren<Renderer>();
        //Vector3 center = obj.transform.position;
        //if (mrs.Length != 0)
        //{
        //    Bounds bounds = new Bounds(center, Vector3.zero);
        //    foreach (Renderer item in mrs)
        //    {
        //        bounds.Encapsulate(item.bounds);
        //    }
        //    center = bounds.center;
        //    print(" Center point ：" + center + " The biggest point ：" + bounds.max + " The smallest ：" + bounds.min);

        //    if ((bounds.max.x - bounds.min.x) > (bounds.max.y - bounds.min.y))
        //    {
        //        maxNum = bounds.max.x - bounds.min.x;
        //    }else if((bounds.max.x - bounds.min.x) < (bounds.max.y - bounds.min.y))
        //    {
        //        maxNum = bounds.max.y - bounds.min.y;
        //    }
        //    else
        //    {
        //        maxNum = bounds.max.x - bounds.min.x;
        //    }
        //    print(maxNum);
        //    // The limit model is too small , Cause positioning too close 
        //    if (maxNum < 8)
        //    {
        //        maxNum = 8;
        //    }
        //    print(maxNum);
        //}
        //centerPoint = center;
//================================================

        // The highlighted 
        Highlighter highlighter = obj.gameObject.AddComponent<Highlighter>();// Add highlight script 
        highlighter.ConstantOn();
    }

    // Update is called once per frame
    void Update()
    {
        // Drag the 
        if (Input.GetMouseButton(2))
        {
            // Adjust the drag sensitivity in real time according to the distance 
            MovingSpeed = Vector3.Distance(transform.position, centerPoint) / 40;
            
            delta_x = Input.GetAxis("Mouse X") * MovingSpeed;
            delta_y = Input.GetAxis("Mouse Y") * MovingSpeed;
            //rotation = Quaternion.Euler(0, transform.rotation.eulerAngles.y, 0);
            //transform.position = rotation * new Vector3(-delta_x, 0, -delta_y) + transform.position;
            transform.Translate(-delta_x, -delta_y, 0);
        }

        // The zoom 
        if (Input.GetAxis("Mouse ScrollWheel") != 0)
        {
            // Zoom distance limit 
            if(Vector3.Distance(transform.position, centerPoint) < 5f)
            {
                delta_z = -Input.GetAxis("Mouse ScrollWheel") * ZoomSpeed;
                if (delta_z > 0)
                {
                    transform.Translate(0, 0, -delta_z);
                }
            }else if (Vector3.Distance(transform.position, centerPoint) > maxNum*2f)
            {
                delta_z = -Input.GetAxis("Mouse ScrollWheel") * ZoomSpeed;
                if (delta_z < 0)
                {
                    transform.Translate(0, 0, -delta_z);
                }
            }
            else
            {
                delta_z = -Input.GetAxis("Mouse ScrollWheel") * ZoomSpeed;
                transform.Translate(0, 0, -delta_z);
            }
        }

        // rotate 
        if (Input.GetMouseButton(1))
        {
            // Adjust the rotation sensitivity according to the distance 
            //distance = Vector3.Distance(transform.position, centerPoint);

            delta_rotation_x = Input.GetAxis("Mouse X") * RotateSpeed;
            delta_rotation_y = -Input.GetAxis("Mouse Y") * RotateSpeed;
            position = transform.rotation * new Vector3(0, 0, distance) + transform.position;
            transform.Rotate(0, delta_rotation_x, 0, Space.World);
            transform.Rotate(delta_rotation_y, 0, 0);
            transform.position = transform.rotation * new Vector3(0, 0, -distance) + position;

            // Rotate the target object 
            //delta_rotation_x = Input.GetAxis("Mouse X") * RotateSpeed;
            //delta_rotation_y = Input.GetAxis("Mouse Y") * RotateSpeed;
            //transform.Rotate(0, delta_rotation_x, 0);
            //transform.Rotate(delta_rotation_y, 0, 0, Space.World);
        }
    }


    /// <summary>
    ///  Get the center point 
    /// </summary>
    /// <param name="target"></param>
    /// <returns></returns>
    private Vector3 GetCenter(GameObject target)
    {
        Renderer[] mrs = target.GetComponentsInChildren<Renderer>();
        Vector3 center = target.transform.position;
        if (mrs.Length != 0)
        {
            Bounds bounds = new Bounds(center, Vector3.zero);
            foreach (Renderer item in mrs)
            {
                bounds.Encapsulate(item.bounds);
            }
            center = bounds.center;
        }
        return center;
    }
}