void OnGUI()
        {
            if (NeedToReload())
            {
                ReloadDataStructures();
            }
            selectedMenuOption = GUI.SelectionGrid(new Rect(5, 8, window.position.width - 10, 20), selectedMenuOption, menuOptions, 3);
            switch (selectedMenuOption)
            {
            case 0:
                ObjectsGUI.Instance.DrawGUI(window);
                AdvancedMenuGUI.Instance.ClearConsole();
                menuOptions[0] = "Objects";
                break;

            case 1:
                ShadersGUI.Instance.DrawGUI(window);
                AdvancedMenuGUI.Instance.ClearConsole();
                menuOptions[0] = "Objects(" + ObjSorter.GetTotalSortedObjects() + ")";
                break;

            case 2:
                AdvancedMenuGUI.Instance.DrawGUI(window);
                menuOptions[0] = "Objects(" + ObjSorter.GetTotalSortedObjects() + ")";
                break;

            default:
                Debug.LogError("Unrecognized menu option: " + selectedMenuOption);
                break;
            }

            if (GUI.Button(new Rect(5, window.position.height - 35, window.position.width / 2 - 10, 33), "Clear Atlas"))
            {
                GameObject[] objsInHierarchy = Utils.GetAllObjectsInHierarchy();
                foreach (GameObject obj in objsInHierarchy)
                {
                    if (obj.name.Contains(Constants.OptimizedObjIdentifier))
                    {
                        DestroyImmediate(obj);
                    }
                    else
                    if (obj.GetComponent <MeshRenderer>() != null)
                    {
                        obj.GetComponent <MeshRenderer>().enabled = true;
                    }
                }
                // delete the folder where the atlas reside.
                string folderOfAtlas = EditorApplication.currentScene;
                if (folderOfAtlas == "")                  //scene is not saved yet.
                {
                    folderOfAtlas = Constants.NonSavedSceneFolderName + ".unity";
                    Debug.LogWarning("WARNING: Scene has not been saved, clearing baked objects from NOT_SAVED_SCENE folder");
                }
                folderOfAtlas = folderOfAtlas.Substring(0, folderOfAtlas.Length - 6) + "-Atlas";  //remove the ".unity"
                if (Directory.Exists(folderOfAtlas))
                {
                    FileUtil.DeleteFileOrDirectory(folderOfAtlas);
                    AssetDatabase.Refresh();
                }
            }

            GUI.enabled = CheckEmptyArray();     //if there are no textures deactivate the GUI
            if (GUI.Button(new Rect(window.position.width / 2, window.position.height - 35, window.position.width / 2 - 5, 33), "Bake Atlas"))
            {
                //Remove objects that are already optimized and start over.
                if (AdvancedMenuGUI.Instance.RemoveObjectsBeforeBaking)
                {
                    GameObject[] objsInHierarchy = Utils.GetAllObjectsInHierarchy();
                    foreach (GameObject obj in objsInHierarchy)
                    {
                        if (obj.name.Contains(Constants.OptimizedObjIdentifier))
                        {
                            GameObject.DestroyImmediate(obj);
                        }
                    }
                }

                List <Rect> texturePositions = new List <Rect>();  //creo que esto puede morir porque el atlasser tiene adentro un rect.
                string      progressBarInfo  = "";
                float       pace             = 1 / (float)ObjSorter.GetRecognizableShadersCount();
                float       progress         = pace;

                Node resultNode = null;    //nodes for the tree for atlasing
                for (int shaderIndex = 0; shaderIndex < ObjSorter.GetObjs().Count; shaderIndex++)
                {
                    EditorUtility.DisplayProgressBar("Optimization in progress... " +
                                                     (AdvancedMenuGUI.Instance.CreatePrefabsForObjects ? " Get coffee this will take some time..." : ""), progressBarInfo, progress);
                    progress += pace;

                    texturePositions.Clear();
                    TextureReuseManager textureReuseManager = new TextureReuseManager();

                    string shaderToAtlas = (ObjSorter.GetObjs()[shaderIndex][0] != null && ObjSorter.GetObjs()[shaderIndex][0].IsCorrectlyAssembled) ? ObjSorter.GetObjs()[shaderIndex][0].ShaderName : "";
                    progressBarInfo = "Processing shader " + shaderToAtlas + "...";
                    int atlasSize = ObjSorter.GetAproxAtlasSize(shaderIndex, AdvancedMenuGUI.Instance.ReuseTextures);

                    if (ShaderManager.Instance.ShaderExists(shaderToAtlas) &&
                        (ObjSorter.GetObjs()[shaderIndex].Count > 1 ||
                         (ObjSorter.GetObjs()[shaderIndex].Count == 1 && ObjSorter.GetObjs()[shaderIndex][0] != null && ObjSorter.GetObjs()[shaderIndex][0].ObjHasMoreThanOneMaterial)) && //more than 1 obj or 1obj wth multiple mat
                        atlasSize < Constants.MaxAtlasSize)                                                                                                                                //check the generated atlas size doesnt exceed max supported texture size
                    {
                        generatedAtlas = new Atlasser(atlasSize, atlasSize);
                        int resizeTimes = 1;

                        for (int j = ObjSorter.GetObjs()[shaderIndex].Count - 1; j >= 0; j--)   //start from the largest to the shortest textures
                        //before atlassing multiple materials obj, combine it.
                        {
                            if (ObjSorter.GetObjs()[shaderIndex][j].ObjHasMoreThanOneMaterial)
                            {
                                progressBarInfo = "Combining materials...";
                                ObjSorter.GetObjs()[shaderIndex][j].ProcessAndCombineMaterials();    //mirar esto, aca esta el problema  de multiple materiales y reimportacion
                            }

                            Vector2 textureToAtlasSize = ObjSorter.GetObjs()[shaderIndex][j].TextureSize;
                            if (AdvancedMenuGUI.Instance.ReuseTextures)
                            {
                                //if texture is not registered already
                                if (!textureReuseManager.TextureRefExists(ObjSorter.GetObjs()[shaderIndex][j]))
                                {
                                    //generate a node
                                    resultNode = generatedAtlas.Insert(Mathf.RoundToInt((textureToAtlasSize.x != Constants.NULLV2.x) ? textureToAtlasSize.x : Constants.NullTextureSize),
                                                                       Mathf.RoundToInt((textureToAtlasSize.y != Constants.NULLV2.y) ? textureToAtlasSize.y : Constants.NullTextureSize));
                                    if (resultNode != null)      //save node if fits in atlas
                                    {
                                        textureReuseManager.AddTextureRef(ObjSorter.GetObjs()[shaderIndex][j], resultNode.NodeRect, j);
                                    }
                                }
                            }
                            else
                            {
                                resultNode = generatedAtlas.Insert(Mathf.RoundToInt((textureToAtlasSize.x != Constants.NULLV2.x) ? textureToAtlasSize.x : Constants.NullTextureSize),
                                                                   Mathf.RoundToInt((textureToAtlasSize.y != Constants.NULLV2.y) ? textureToAtlasSize.y : Constants.NullTextureSize));
                            }

                            if (resultNode == null)
                            {
                                int resizedAtlasSize = atlasSize + Mathf.RoundToInt((float)atlasSize * Constants.AtlasResizeFactor * resizeTimes);
                                generatedAtlas = new Atlasser(resizedAtlasSize, resizedAtlasSize);
                                j = ObjSorter.GetObjs()[shaderIndex].Count;    //Count and not .Count-1 bc at the end of the loop it will be substracted j-- and we want to start from Count-1

                                texturePositions.Clear();
                                textureReuseManager.ClearTextureRefs();
                                resizeTimes++;
                            }
                            else
                            {
                                if (AdvancedMenuGUI.Instance.ReuseTextures)
                                {
                                    texturePositions.Add(textureReuseManager.GetTextureRefPosition(ObjSorter.GetObjs()[shaderIndex][j]));
                                }
                                else
                                {
                                    texturePositions.Add(resultNode.NodeRect);    //save the texture rectangle
                                }
                            }
                        }
                        progressBarInfo = "Saving textures to atlas...";
                        Material atlasMaterial = CreateAtlasMaterialAndTexture(shaderToAtlas, shaderIndex, textureReuseManager);
                        progressBarInfo = "Remapping coordinates...";

                        ObjSorter.OptimizeDrawCalls(ref atlasMaterial,
                                                    shaderIndex,
                                                    generatedAtlas.GetAtlasSize().x,
                                                    generatedAtlas.GetAtlasSize().y,
                                                    texturePositions,
                                                    AdvancedMenuGUI.Instance.ReuseTextures,
                                                    textureReuseManager,
                                                    AdvancedMenuGUI.Instance.CreatePrefabsForObjects);
                    }
                }

                //after the game object has been organized, remove the combined game objects.
                for (int shaderIndex = 0; shaderIndex < ObjSorter.GetObjs().Count; shaderIndex++)
                {
                    for (int j = ObjSorter.GetObjs()[shaderIndex].Count - 1; j >= 0; j--)
                    {
                        if (ObjSorter.GetObjs()[shaderIndex][j].ObjWasCombined)
                        {
                            ObjSorter.GetObjs()[shaderIndex][j].ClearCombinedObject();
                        }
                    }
                }
                EditorUtility.ClearProgressBar();
                AssetDatabase.Refresh();    //reimport the created atlases so they get displayed in the editor.
            }
        }