Unity 3D Render Camera Bug!!!

Hi, there

I developing 2D game

I want render 3d models in Unity

I writted some script for render and save png file with alpha channel

 using UnityEngine;
 using UnityEditor;
 using System.Collections;
 using System.IO;
 
 public class PhotoTool : MonoBehaviour 
 {
     
     private string path;
     public bool shot = false;
     public Camera cam;
 
     public string color;
     public Transform unit;
 
     void Start()
     {
         if (path == null)
         {
             SelectDir ();
         }
 
         int angle = 0;
         for (int i = 0; i < 8; i++) 
         {
             Shot ();
             angle += 45;
             unit.localEulerAngles = Vector3.up * angle;
         }
 
 
     }
         
 
     public void Shot()
     {
         int sqr = 512;
 
         RenderTexture tempRT = new RenderTexture(sqr,sqr, 0 );
 
         cam.targetTexture = tempRT;
         cam.Render();
 
         RenderTexture.active = tempRT;
         Texture2D virtualPhoto = new Texture2D(sqr,sqr, TextureFormat.ARGB32, false);
         virtualPhoto.ReadPixels( new Rect(0, 0, sqr,sqr), 0, 0);
 
         RenderTexture.active = null;
         cam.targetTexture = null;
 
         byte[] bytes = virtualPhoto.EncodeToPNG();
 
         File.WriteAllBytes(path + "/"+ unit.name + "_" + color + "_" + unit.transform.localEulerAngles.y + ".png", bytes);
     }
 
     public void SelectDir()
     {
         path = EditorUtility.OpenFolderPanel ("","","");
     }
 
 
 }

So this scripts works, but i get uncorrect render

Look: There is expected result (used simple screenshot)

But i got this

So, how to fix this? I checked this on 5.2.2 | 5.3.4 | 5.4.0b but same result

Thanks, Unity Community