finished

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

public class change_prefab : MonoBehaviour
{
    public GameObject[] targetObjects;
    public Mesh[] targetMesh;
    Renderer rend;
    bool isobjVisible = false;
    bool objSpawned = false;
    int i = 0;
    float frequency = 0.1f;
    public float min, max;

    private void Start()
    {
        rend = GetComponent<Renderer>();

        int index = Random.Range(0, targetObjects.Length);
        this.GetComponent<MeshRenderer>().materials = targetObjects[index].GetComponent<MeshRenderer>().sharedMaterials;
        this.GetComponent<MeshFilter>().sharedMesh = targetMesh[index];
    }

    void Update()
    {
        if(Time.time >= frequency)
        {
            float delay = Random.Range(min, max);
            if (rend.IsVisibleFrom(Camera.main))
            {
                isobjVisible = true;
            }
            else
            {
                isobjVisible = false;
                objSpawned = false;
            }

            if (isobjVisible == false && objSpawned == false)
            {
                int index = Random.Range(0, targetObjects.Length);
                this.GetComponent<MeshRenderer>().materials = targetObjects[index].GetComponent<MeshRenderer>().sharedMaterials;
                this.GetComponent<MeshFilter>().sharedMesh = targetMesh[index];
                objSpawned = true;
            }
            i++;
            Debug.Log(i);
            frequency = Time.time + delay;
        }

    }
}