Unity, Рендеринг в текстуру и ее сохранение

private Texture2D RT_Texture(Texture mainTexture)
        {

            Texture2D texture2D = new Texture2D(mainTexture.width, mainTexture.height, TextureFormat.ARGB32, false);//RGB24
  
            RenderTexture currentRT = RenderTexture.active;

            RenderTexture renderTexture = new RenderTexture(mainTexture.width, mainTexture.height, 32);
            Graphics.Blit(mainTexture, renderTexture);

            RenderTexture.active = renderTexture;
            texture2D.ReadPixels(new Rect(0, 0, renderTexture.width, renderTexture.height), 0, 0);
            texture2D.Apply();

            Color[] pixels = texture2D.GetPixels();

            RenderTexture.active = currentRT;

            return texture2D;
        }

public void MeshToFile(Mesh m, Material[] mats, string filename, string model_folder)
        {
            //a filename is fullpath
            using (StreamWriter sw = new StreamWriter(filename))
            {
        sw.Write(MeshToString(m, mats));
            }
            for (int material = 0; material < m.subMeshCount; material++)
            {

                var tex = RT_Texture(mats[material].mainTexture);
                if (tex)
                {
                    byte[] texture_bytes = ImageConversion.EncodeToPNG(tex);
                    File.WriteAllBytes(model_folder + @"\" + mats[material].mainTexture.name + ".png", texture_bytes);
                }
                else
                    //log
            }
            
         }

            RenderTexture.active = renderTexture;
            texture2D.ReadPixels(new Rect(0, 0, renderTexture.width, renderTexture.height), 0, 0);
            texture2D.Apply();

            Color[] pixels = texture2D.GetPixels();
            for(int i = 0; i < pixels.Length; i++)
            {
                        pixels[i].a = 1.0f;
            }
            texture2D.SetPixels();
            texture2D.Apply();