using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using UnityEditor.SceneManagement;
using UnityEditorInternal;
using UnityEngine;
using UnityEngine.Experimental.Rendering;
using UnityEngine.TerrainTools;

namespace UnityEditor.TerrainTools
{
    [Serializable]
    internal class UtilitySettings : ScriptableObject
    {
        // Terrain Split
        public int TileSplit = 2;
        public bool AutoUpdateSettings = true;
        public string TerrainAssetDir = "Assets/Terrain";

        // Layers
        public string PalettePath = string.Empty;
        public bool ApplyAllTerrains = true;

        // Replace splatmap
        public Terrain SplatmapTerrain;
        public Texture2D SplatmapOld0;
        public Texture2D SplatmapNew0;
        public Texture2D SplatmapOld1;
        public Texture2D SplatmapNew1;
        public ImageFormat SelectedFormat = ImageFormat.TGA;
        public RotationAdjustment RotationAdjust = RotationAdjustment.Clockwise;
        public FlipAdjustment FlipAdjust = FlipAdjustment.Horizontal;
        public string SplatFolderPath = "Assets/Splatmaps/";
        public bool AdjustAllSplats = false;

        // Import heightmap
        public Texture2D HeightmapImport;
        public int HeightmapResolution;
        public float ImportHeightRemapMin;
        public float ImportHeightRemapMax;
        public Heightmap.Flip HeightmapFlipMode = Heightmap.Flip.None;

        // Export heightmaps
        public string HeightmapFolderPath = "Assets/Heightmaps/";
        public Heightmap.Format HeightFormat = Heightmap.Format.RAW;
        public Heightmap.Depth HeightmapDepth = Heightmap.Depth.Bit16;
        public ToolboxHelper.ByteOrder HeightmapByteOrder = ToolboxHelper.ByteOrder.Windows;
        public float ExportHeightRemapMin = 0.0f;
        public float ExportHeightRemapMax = 1.0f;
        public bool FlipVertically = false;
        
        // Remap heightmaps
        public int LowerBound = 0;
        public int UpperBound = 512;
        public float BottomPad = 0.05f;
        public float TopPad = 0.05f;

        // Enums
        public enum ImageFormat { TGA, PNG }
        public enum SplatmapChannel { R, G, B, A }
        public enum RotationAdjustment { Clockwise, Counterclockwise }
        public enum FlipAdjustment { Horizontal, Vertical }

        // GUI
        public bool ShowTerrainEdit = false;
        public bool ShowTerrainLayers = false;
        public bool ShowReplaceSplatmaps = false;
        public bool ShowExportSplatmaps = false;
        public bool ShowExportHeightmaps = false;
        public bool ShowRemapHeightmaps = false;
    }

    internal class TerrainToolboxUtilities
    {
        internal UtilitySettings m_Settings = ScriptableObject.CreateInstance<UtilitySettings>();

        // Splatmaps
        int m_SplatmapResolution = 0;
        Terrain[] m_SplatExportTerrains;
        // Terrain Edit
        Terrain[] m_Terrains;
        List<Material> m_TerrainMaterials = new List<Material>();
        // Terrain Split
        Terrain[] m_SplitTerrains;
        // Layers
        List<TerrainLayer> m_CopiedLayers = new List<TerrainLayer>();
        internal List<Layer> m_PaletteLayers = new List<Layer>();
        ReorderableList m_LayerList;
        TerrainPalette m_SelectedLayerPalette = ScriptableObject.CreateInstance<TerrainPalette>();
        bool m_LayersAlreadyAdded = false;
        // Heightmap export
        Dictionary<string, Heightmap.Depth> m_DepthOptions = new Dictionary<string, Heightmap.Depth>()
        {
            { "16 bit", Heightmap.Depth.Bit16 },
            { "8 bit", Heightmap.Depth.Bit8 }
        };
        internal int m_SelectedDepth = 0;

        // Splatmaps
        internal List<Texture2D> m_Splatmaps = new List<Texture2D>();
        HashSet<Texture2D> m_SplatmapHasCopy = new HashSet<Texture2D>();
        internal ReorderableList m_SplatmapList;
        int m_SelectedSplatMap = 0;
        bool m_PreviewIsDirty = false;
        MaterialPropertyBlock m_PreviewMaterialPropBlock = new MaterialPropertyBlock();
        ToolboxHelper.RenderPipeline m_ActiveRenderPipeline = ToolboxHelper.RenderPipeline.None;

        //Visualization
        Material m_PreviewMaterial;
        bool m_ShowSplatmapPreview = false;
#if UNITY_2019_2_OR_NEWER
#else
        Terrain.MaterialType m_TerrainMaterialType;
        float m_TerrainLegacyShininess;
        Color m_TerrainLegacySpecular;
#endif
        int m_MaxLayerCount = 0;
        int m_MaxSplatmapCount = 0;

        const int k_MaxLayerHD = 8; // HD allows up to 8 layers with 2 splat alpha maps
        const int k_MaxSplatmapHD = 2;
        const int k_MaxNoLimit = 20;
        const int k_MinHeightmapRes = 32;
        const int k_MinDetailResPerPatch = 8;

        static class Styles
        {
            public static readonly GUIContent TerrainLayers = EditorGUIUtility.TrTextContent("Terrain Layers");
            public static readonly GUIContent ImportSplatmaps = EditorGUIUtility.TrTextContent("Terrain Splatmaps");
            public static readonly GUIContent ExportSplatmaps = EditorGUIUtility.TrTextContent("Export Splatmaps");
            public static readonly GUIContent ExportHeightmaps = EditorGUIUtility.TrTextContent("Export Heightmaps");
            public static readonly GUIContent TerrainEdit = EditorGUIUtility.TrTextContent("Terrain Edit");
            public static readonly GUIContent DuplicateTerrain = EditorGUIUtility.TrTextContent("Duplicate");
            public static readonly GUIContent RemoveTerrain = EditorGUIUtility.TrTextContent("Clean Remove");
            public static readonly GUIContent SplitTerrain = EditorGUIUtility.TrTextContent("Split");

            public static readonly GUIContent DuplicateTerrainBtn = EditorGUIUtility.TrTextContent("Duplicate", "Start duplicating selected terrain(s) and create new terrain data.");
            public static readonly GUIContent RemoveTerrainBtn = EditorGUIUtility.TrTextContent("Remove", "Start removing selected terrain(s) and delete terrain data asset files.");

            public static readonly GUIContent PalettePreset = EditorGUIUtility.TrTextContent("Layer Palette Profile", "Select or make a Terrain Layer palette profile asset.");
            public static readonly GUIContent SavePalette = EditorGUIUtility.TrTextContent("Save", "Save the current palette asset file on disk.");
            public static readonly GUIContent SaveAsPalette = EditorGUIUtility.TrTextContent("Save As", "Save the current palette asset as a new file on disk.");
            public static readonly GUIContent RefreshPalette = EditorGUIUtility.TrTextContent("Refresh", "Load selected palette and apply to list of layers.");
            public static readonly GUIContent ApplyToAllTerrains = EditorGUIUtility.TrTextContent("All Terrains in Scene", "When unchecked only apply layer changes to selected terrain(s).");
            public static readonly GUIContent ImportTerrainLayersBtn = EditorGUIUtility.TrTextContent("Import From Terrain", "Import layers from the selected terrain.");
            public static readonly GUIContent AddLayersBtn = EditorGUIUtility.TrTextContent("Add Layers", "Add layers to the selected terrain(s) that aren't already in the palette.");
            public static readonly GUIContent ReplacesLayersBtn = EditorGUIUtility.TrTextContent("Replace Layers", "Replace layers assigned to selected terrain(s). Removed layers will not alter the splatmap data.");
            public static readonly GUIContent RemoveLayersBtn = EditorGUIUtility.TrTextContent("Remove All Layers", "Remove all layers from selected terrain(s)");

            public static readonly GUIContent TerrainToReplaceSplatmap = EditorGUIUtility.TrTextContent("Terrain", "Select a terrain to replace splatmaps on.");
            public static readonly GUIContent SplatmapResolution = EditorGUIUtility.TrTextContent("Splatmap Resolution: ", "The control texture resolution setting of selected terrain.");
            public static readonly GUIContent SplatAlpha0 = EditorGUIUtility.TrTextContent("Old SplatAlpha0", "The SplatAlpha 0 texture from selected terrain.");
            public static readonly GUIContent SplatAlpha1 = EditorGUIUtility.TrTextContent("Old SplatAlpha1", "The SplatAlpha 1 texture from selected terrain.");
            public static readonly GUIContent SplatAlpha0New = EditorGUIUtility.TrTextContent("New SplatAlpha0", "Select a texture to replace the SplatAlpha 0 texture on selected terrain.");
            public static readonly GUIContent SplatAlpha1New = EditorGUIUtility.TrTextContent("New SplatAlpha1", "Select a texture to replace the SplatAlpha 1 texture on selected terrain.");
            public static readonly GUIContent ImportFromSplatmapBtn = EditorGUIUtility.TrTextContent("Import from Selected Terrain", "Import splatmaps from the selected terrain.");
            public static readonly GUIContent ReplaceSplatmapsBtn = EditorGUIUtility.TrTextContent("Replace Splatmaps", "Replace splatmaps with new splatmaps on selected terrain.");
            public static readonly GUIContent ResetSplatmapsBtn = EditorGUIUtility.TrTextContent("Reset Splatmaps", "Clear splatmap textures on selected terrain(s).");
            public static readonly GUIContent ExportToTerrSplatmapBtn = EditorGUIUtility.TrTextContent("Apply to Terrain", "Export splatmaps to selected terrains.");
            public static readonly GUIContent PreviewSplatMapTogg = EditorGUIUtility.TrTextContent("Preview Splatmap", "Preview a splatmap on selected terrains.");
            public static readonly GUIContent RotateSplatmapLabel = EditorGUIUtility.TrTextContent("Rotate Adjustment", "Select whether to rotate clockwise or counterclockwise.");
            public static readonly GUIContent FlipSplatmapLabel = EditorGUIUtility.TrTextContent("Flip Adjustment", "Select whether to flip horizontally or vertically.");
            public static readonly GUIContent RotateSplatmapBtn = EditorGUIUtility.TrTextContent("Rotate", "Rotate splatmap in the selected direction.");
            public static readonly GUIContent FlipSplatmapBtn = EditorGUIUtility.TrTextContent("Flip", "Flip splatmaps in the selected direction.");
            public static readonly GUIContent MultiAdjustTogg = EditorGUIUtility.TrTextContent("Adjust All Splatmaps", "Make changes to all splatmaps.");
            public static readonly GUIContent ExportSplatmapFolderPath = EditorGUIUtility.TrTextContent("Export Folder Path", "Select or input a folder path where splatmap textures will be saved.");
            public static readonly GUIContent ExportSplatmapFormat = EditorGUIUtility.TrTextContent("Splatmap Format", "Texture format of exported splatmap(s).");
            public static readonly GUIContent ExportSplatmapsBtn = EditorGUIUtility.TrTextContent("Export Splatmaps", "Start exporting splatmaps into textures as selected format from selected terrain(s).");

            public static readonly GUIContent OriginalTerrain = EditorGUIUtility.TrTextContent("Original Terrain", "Select a terrain to split into smaller tiles.");
            public static readonly GUIContent TileSplit = EditorGUIUtility.TrTextContent("Split Tiles", "The number of tiles along the X and Z axes after splitting.");
            public static readonly GUIContent AutoUpdateSetting = EditorGUIUtility.TrTextContent("Auto Update Terrain Settings", "Automatically copy terrain settings to new tiles from original tiles upon create.");
            public static readonly GUIContent KeepOldTerrains = EditorGUIUtility.TrTextContent("Keep Original Terrain", "Keep original terrain while splitting.");
            public static readonly GUIContent SplitTerrainBtn = EditorGUIUtility.TrTextContent("Split", "Start splitting original terrain into small tiles.");

            public static readonly GUIContent ExportHeightmapsBtn = EditorGUIUtility.TrTextContent("Export Heightmaps", "Start exporting raw heightmaps for selected terrain(s).");
            public static readonly GUIContent HeightmapSelectedFormat = EditorGUIUtility.TrTextContent("Heightmap Format", "Select the image format for exported heightmaps.");
            public static readonly GUIContent ExportHeightmapFolderPath = EditorGUIUtility.TrTextContent("Export Folder Path", "Select or input a folder path where heightmaps will be saved.");
            public static readonly GUIContent HeightmapBitDepth = EditorGUIUtility.TrTextContent("Heightmap Depth", "Select heightmap depth option from 8 bit or 16 bit.");
            public static readonly GUIContent HeightmapByteOrder = EditorGUIUtility.TrTextContent("Heightmap Byte Order", "Select heightmap byte order from Windows or Mac.");
            public static readonly GUIContent HeightmapRemap = EditorGUIUtility.TrTextContent("Levels Correction", "Remap the height range before export.");
            public static readonly GUIContent HeightmapRemapMin = EditorGUIUtility.TrTextContent("Min", "Minimum input height");
            public static readonly GUIContent HeightmapRemapMax = EditorGUIUtility.TrTextContent("Max", "Maximum input height");
            public static readonly GUIContent FlipVertically = EditorGUIUtility.TrTextContent("Flip Vertically", "Flip heights vertically when export. Enable this if using heightmap in external program like World Machine. Or use the Flip Y Axis option in World Machine instead.");

            public static readonly GUIContent RemapHeightMaps = EditorGUIUtility.TrTextContent("Remap Height Maps", "Remap height values while preserving the visual appearance");
            public static readonly GUIContent RemapLabel  = EditorGUIUtility.TrTextContent("Remap Terrain Height Range");
            public static readonly GUIContent OptimizeLabel  = EditorGUIUtility.TrTextContent("Optimize Height Range Usage");
            public static readonly GUIContent RemapButtonLabel  = EditorGUIUtility.TrTextContent("Remap", "Remap heightmap between supplied height values, preserving the existing position");
            public static readonly GUIContent OptimizeButtonLabel  = EditorGUIUtility.TrTextContent("Optimize", "Remap the heightmap so that it fills the height values efficiently");

            public static readonly GUIStyle ToggleButtonStyle = "LargeButton";
            
            // for the large buttons 
            public static int ButtonWidth = 140; 
            public static int ButtonHeight = 25; 
        }

        public static void DrawSeperatorLine()
        {
            Rect rect = EditorGUILayout.GetControlRect(GUILayout.Height(12));
            rect.height = 1;
            rect.y = rect.y + 5;
            rect.x = 2;
            rect.width += 6;
            EditorGUI.DrawRect(rect, new Color(0.35f, 0.35f, 0.35f));
        }

        public void OnLoad()
        {
            if (m_Settings.PalettePath != string.Empty && File.Exists(m_Settings.PalettePath))
            {
                LoadPalette();
            }
        }

        public void OnGUI()
        {
            // scroll view of settings
            EditorGUIUtility.hierarchyMode = true;
            DrawSeperatorLine();

            // Terrain Edit			
            m_Settings.ShowTerrainEdit = TerrainToolGUIHelper.DrawHeaderFoldout(Styles.TerrainEdit, m_Settings.ShowTerrainEdit);
            ++EditorGUI.indentLevel;
            if (m_Settings.ShowTerrainEdit)
            {
                ShowTerrainEditGUI();
            }
            --EditorGUI.indentLevel;
            DrawSeperatorLine();

            // Terrain Layers
            m_Settings.ShowTerrainLayers = TerrainToolGUIHelper.DrawHeaderFoldout(Styles.TerrainLayers, m_Settings.ShowTerrainLayers);
            ++EditorGUI.indentLevel;
            if (m_Settings.ShowTerrainLayers)
            {
                ShowTerrainLayerGUI();
            }
            --EditorGUI.indentLevel;
            DrawSeperatorLine();

            // Terrain Splatmaps
            m_Settings.ShowReplaceSplatmaps = TerrainToolGUIHelper.DrawHeaderFoldout(Styles.ImportSplatmaps, m_Settings.ShowReplaceSplatmaps);
            ++EditorGUI.indentLevel;
            if (m_Settings.ShowReplaceSplatmaps)
            {
                ShowSplatmapImportGUI();
            }
            --EditorGUI.indentLevel;
            DrawSeperatorLine();
            
            // Terrain Heightmaps
            m_Settings.ShowRemapHeightmaps =
                TerrainToolGUIHelper.DrawHeaderFoldout(Styles.RemapHeightMaps, m_Settings.ShowRemapHeightmaps);
            ++EditorGUI.indentLevel;
            if (m_Settings.ShowRemapHeightmaps)
            {
                ShowHeightRemapGUI();
            }
            --EditorGUI.indentLevel;
            DrawSeperatorLine();

            // Export Spaltmaps
            m_Settings.ShowExportSplatmaps = TerrainToolGUIHelper.DrawHeaderFoldout(Styles.ExportSplatmaps, m_Settings.ShowExportSplatmaps);
            ++EditorGUI.indentLevel;
            if (m_Settings.ShowExportSplatmaps)
            {
                ShowExportSplatmapGUI();
            }
            --EditorGUI.indentLevel;
            DrawSeperatorLine();

            // Export Heightmaps
            m_Settings.ShowExportHeightmaps = TerrainToolGUIHelper.DrawHeaderFoldout(Styles.ExportHeightmaps, m_Settings.ShowExportHeightmaps);
            ++EditorGUI.indentLevel;
            if (m_Settings.ShowExportHeightmaps)
            {
                ShowExportHeightmapGUI();
            }
            --EditorGUI.indentLevel;

            EditorGUILayout.Space();
        }

        void ShowTerrainEditGUI()
        {
            // style for labels 
            GUIStyle labelStyle = new GUIStyle(EditorStyles.label); 
            labelStyle.wordWrap = true; 
            
            // Duplicate Terrain
            EditorGUILayout.LabelField(Styles.DuplicateTerrain, EditorStyles.boldLabel);
            ++EditorGUI.indentLevel;
            EditorGUILayout.BeginHorizontal();
            EditorGUILayout.LabelField("Select terrain(s) to make a copy from with new terrain data assets: ", labelStyle);
            if (GUILayout.Button(Styles.DuplicateTerrainBtn, GUILayout.Height(Styles.ButtonHeight), GUILayout.Width(Styles.ButtonWidth)))
            {
                DuplicateTerrains();
            }
            EditorGUILayout.EndHorizontal();

            // Clean Delete
            --EditorGUI.indentLevel;
            EditorGUILayout.LabelField(Styles.RemoveTerrain, EditorStyles.boldLabel);
            ++EditorGUI.indentLevel;
            EditorGUILayout.BeginHorizontal();
            EditorGUILayout.LabelField("Select terrain components to remove and delete associated terrain data assets: ", labelStyle);
            if (GUILayout.Button(Styles.RemoveTerrainBtn, GUILayout.Height(Styles.ButtonHeight), GUILayout.Width(Styles.ButtonWidth)))
            {
                RemoveTerrains();
            }
            EditorGUILayout.EndHorizontal();

            // Split Terrain
            --EditorGUI.indentLevel;
            EditorGUILayout.LabelField(Styles.SplitTerrain, EditorStyles.boldLabel);
            ++EditorGUI.indentLevel;
            EditorGUILayout.LabelField("Select terrain(s) to split: ");
            m_Settings.TileSplit = EditorGUILayout.IntField(Styles.TileSplit, m_Settings.TileSplit);
            m_Settings.AutoUpdateSettings = EditorGUILayout.Toggle(Styles.AutoUpdateSetting, m_Settings.AutoUpdateSettings);
            EditorGUILayout.BeginHorizontal();
            EditorGUILayout.Space();
            if (GUILayout.Button(Styles.SplitTerrainBtn, GUILayout.Height(Styles.ButtonHeight), GUILayout.Width(Styles.ButtonWidth)))
            {
                SplitTerrains();
            }
            EditorGUILayout.EndHorizontal();
            --EditorGUI.indentLevel;
        }

        void ShowTerrainLayerGUI()
        {
            // Layer Palette preset
            EditorGUILayout.LabelField(Styles.PalettePreset);
            EditorGUI.BeginChangeCheck();
            m_SelectedLayerPalette = (TerrainPalette)EditorGUILayout.ObjectField(m_SelectedLayerPalette, typeof(TerrainPalette), false);
            if (EditorGUI.EndChangeCheck() && m_SelectedLayerPalette != null)
            {
                if (EditorUtility.DisplayDialog("Confirm", "Load palette from selected?", "OK", "Cancel"))
                {
                    LoadPalette();
                }
            }
            EditorGUILayout.BeginHorizontal();
            if (GUILayout.Button(Styles.SavePalette))
            {
                if (GetPalette())
                {
                    m_SelectedLayerPalette.PaletteLayers.Clear();
                    foreach (var layer in m_PaletteLayers)
                    {
                        m_SelectedLayerPalette.PaletteLayers.Add(layer.AssignedLayer);
                    }
                    AssetDatabase.SaveAssets();
                }
            }
            if (GUILayout.Button(Styles.SaveAsPalette))
            {
                CreateNewPalette();
            }
            if (GUILayout.Button(Styles.RefreshPalette))
            {
                if (GetPalette())
                {
                    LoadPalette();
                }
            }
            EditorGUILayout.EndHorizontal();

            // layer reorderable list
            ShowLayerListGUI();

            // Apply button			
            m_Settings.ApplyAllTerrains = EditorGUILayout.Toggle(Styles.ApplyToAllTerrains, m_Settings.ApplyAllTerrains);
            if (m_LayersAlreadyAdded)
            {
                EditorGUILayout.HelpBox("One or more of the layers are already in your terrain palette.", MessageType.Info);
            }
            EditorGUILayout.BeginHorizontal();
            EditorGUILayout.Space();
            if (GUILayout.Button(Styles.AddLayersBtn, GUILayout.Height(Styles.ButtonHeight), GUILayout.MaxWidth(Styles.ButtonWidth)))
            {
                AddLayersToSelectedTerrains(false);
            }
            if (GUILayout.Button(Styles.ReplacesLayersBtn, GUILayout.Height(Styles.ButtonHeight), GUILayout.MaxWidth(Styles.ButtonWidth)))
            {
                AddLayersToSelectedTerrains(true);
            }
            // Clear button
            if (GUILayout.Button(Styles.RemoveLayersBtn, GUILayout.Height(Styles.ButtonHeight), GUILayout.MaxWidth(Styles.ButtonWidth)))
            {
                RemoveLayersFromSelectedTerrains();
            }
            EditorGUILayout.EndHorizontal();
        }

        // layer list view
        const int kElementHeight = 70;
        const int kElementObjectFieldHeight = 16;
        const int kElementPadding = 2;
        const int kElementObjectFieldWidth = 240;
        const int kElementToggleWidth = 20;
        const int kElementImageWidth = 64;
        const int kElementImageHeight = 64;

        void ShowLayerListGUI()
        {
            EditorGUILayout.BeginVertical("Box");
            if (GUILayout.Button(Styles.ImportTerrainLayersBtn, GUILayout.Width(Styles.ButtonWidth)))
            {
                ImportLayersFromTerrain();
            }
            // List View
            if (m_LayerList == null)
            {
                m_LayerList = new ReorderableList(m_PaletteLayers, typeof(Layer), true, true, true, true);
            }

            m_LayerList.elementHeight = kElementHeight;
            m_LayerList.drawHeaderCallback = (Rect rect) => EditorGUI.LabelField(rect, "Layer Palette");
            m_LayerList.drawElementCallback = DrawLayerElement;
            m_LayerList.onAddCallback = OnAddLayerElement;
            m_LayerList.onRemoveCallback = OnRemoveLayerElement;
            m_LayerList.onCanAddCallback = OnCanAddLayerElement;
            m_LayerList.DoLayoutList();
            LayerCreation(); 
            EditorGUILayout.EndVertical();
        }

        void DrawLayerElement(Rect rect, int index, bool selected, bool focused)
        {
            rect.y = rect.y + kElementPadding;
            var rectImage = new Rect((rect.x + kElementPadding), rect.y, kElementImageWidth, kElementImageHeight);
            var rectObject = new Rect((rectImage.x + kElementImageWidth), rect.y, kElementObjectFieldWidth, kElementObjectFieldHeight);

            if (m_PaletteLayers.Count > 0 && m_PaletteLayers[index] != null)
            {
                EditorGUI.BeginChangeCheck();
                EditorGUILayout.BeginHorizontal();
                List<TerrainLayer> existLayers = m_PaletteLayers.Select(l => l.AssignedLayer).ToList();
                TerrainLayer oldLayer = m_PaletteLayers[index].AssignedLayer;
                Texture2D icon = null;
                if (m_PaletteLayers[index].AssignedLayer != null)
                {
                    icon = AssetPreview.GetAssetPreview(m_PaletteLayers[index].AssignedLayer.diffuseTexture);
                }
                GUI.Box(rectImage, icon);
                m_PaletteLayers[index].AssignedLayer = EditorGUI.ObjectField(rectObject, m_PaletteLayers[index].AssignedLayer, typeof(TerrainLayer), false) as TerrainLayer;
                EditorGUILayout.EndHorizontal();
                if (EditorGUI.EndChangeCheck())
                {
                    if (existLayers.Contains(m_PaletteLayers[index].AssignedLayer) && m_PaletteLayers[index].AssignedLayer != oldLayer)
                    {
                        EditorUtility.DisplayDialog("Error", "Layer exists. Please select a different layer.", "OK");
                        m_PaletteLayers[index].AssignedLayer = oldLayer;
                    }
                }
            }
        }

        bool OnCanAddLayerElement(ReorderableList list)
        {
            return list.count < m_MaxLayerCount;
        }

        // adding layers 
        int m_LayerPickerWindowID = -1;
        int m_ObjPickerWindowID = -1;
        string m_LayerName = "NewLayer";
        TerrainLayer m_PickedLayer;
        Texture2D m_LayerTexture;
        void OnAddLayerElement(ReorderableList list)
        {
            m_LayerPickerWindowID = EditorGUIUtility.GetControlID(FocusType.Passive) + 200; // had to bump this to make it unique
            EditorGUIUtility.ShowObjectPicker<TerrainLayer>(null, false, "", m_LayerPickerWindowID);
        }

        void LayerCreation()
        {
            // this code grabs the layer from the ObjectSelector, and creates a new layer with the texture and adds
            // it to the list 
            if (Event.current.commandName == "ObjectSelectorClosed" &&
                EditorGUIUtility.GetObjectPickerControlID() == m_LayerPickerWindowID)
            {
                m_PickedLayer = (TerrainLayer)EditorGUIUtility.GetObjectPickerObject();
            }

            if (m_PickedLayer != null && Event.current.type == EventType.Repaint)
            {
                TerrainLayer tempLayer = m_PickedLayer;
                m_PickedLayer = null;
                AddLayerElement(tempLayer);
            }

            if (Event.current.commandName == "ObjectSelectorClosed" &&
                EditorGUIUtility.GetObjectPickerControlID() == m_ObjPickerWindowID)
            {
                m_LayerTexture = (Texture2D)EditorGUIUtility.GetObjectPickerObject();
            }

            if (m_LayerTexture != null && Event.current.type == EventType.Repaint)
            {
                Texture2D tempTexture = m_LayerTexture;
                m_LayerTexture = null;
                CreateNewLayerWithTexture(tempTexture);
            }
            
            RemoveEmptyLayers(); 
        }
        
        void AddLayerElement(TerrainLayer layer)
        {
            if (LayerExists(layer))
            {
                return;
            }
            Layer newLayer = new Layer();
            newLayer.AssignedLayer = layer;
            newLayer.IsSelected = true;
            m_PaletteLayers.Add(newLayer);
            m_LayerList.index = m_PaletteLayers.Count - 1;
        }
        
        bool LayerExists(TerrainLayer layer)
        {
            List<TerrainLayer> existingLayers = m_PaletteLayers.Select(l => l.AssignedLayer).ToList();

            if(existingLayers.Count > 0 && existingLayers.Contains(layer))
            {
                m_LayerList.index = existingLayers.IndexOf(layer);
                return true;
            }
            
            return false;
        }

        void RemoveEmptyLayers()
        {
            m_PaletteLayers.RemoveAll(layer => layer.AssignedLayer == null);
        }
        
        void CreateNewLayerWithTexture(Texture2D texture)
        {
            Layer newLayer = new Layer();
            newLayer.AssignedLayer = new TerrainLayer();
            newLayer.AssignedLayer.diffuseTexture = texture;
            m_PaletteLayers.Add(newLayer);
            m_LayerList.index = m_PaletteLayers.Count - 1;

            string path = "Assets";
            foreach (UnityEngine.Object obj in Selection.GetFiltered(typeof(UnityEngine.Object), SelectionMode.Assets))
            {
                path = AssetDatabase.GetAssetPath(obj);
                if (!string.IsNullOrEmpty(path) && File.Exists(path))
                {
                    path = Path.GetDirectoryName(path);
                    break;
                }
            }
            newLayer.AssignedLayer.name = m_LayerName;
            AssetDatabase.CreateAsset(newLayer.AssignedLayer, AssetDatabase.GenerateUniqueAssetPath($"{path}/{m_LayerName}.terrainlayer"));
        }

        void OnRemoveLayerElement(ReorderableList list)
        {
            m_PaletteLayers.RemoveAt(list.index);
            list.index = list.index - 1;
        }

        void ShowSplatmapImportGUI()
        {
            EditorGUILayout.BeginVertical("Box");
            if (GUILayout.Button(Styles.ImportFromSplatmapBtn, GUILayout.Width(Styles.ButtonWidth + 35)))
            {
                ImportSplatmapsFromTerrain();
            }
            if (m_SplatmapList == null)
            {
                m_SplatmapList = new ReorderableList(m_Splatmaps, typeof(Texture2D), true, false, true, true);
            }
            m_SplatmapList.elementHeight = 70;
            m_SplatmapList.drawHeaderCallback = (Rect rect) => EditorGUI.LabelField(rect, "Splatmaps");
            m_SplatmapList.drawElementCallback = DrawSplatmapElement;
            m_SplatmapList.onAddCallback = OnAddSplatmapElement;
            m_SplatmapList.onRemoveCallback = OnRemoveSplatmapElement;
            m_SplatmapList.onCanAddCallback = OnCanAddSplatmapElement;
            m_SplatmapList.onSelectCallback = OnSelectSplatmapElement;

            EditorGUI.BeginChangeCheck();
            m_SplatmapList.DoLayoutList();
            if (EditorGUI.EndChangeCheck())
            {
                // check to see if any of the splatmaps in the list need to be copied
                for (int i = 0; i < m_Splatmaps.Count; i++)
                {
                    var splatmap = m_Splatmaps[i];
                    if (splatmap != null && !m_SplatmapHasCopy.Contains(splatmap))
                    {
                        var textureCopy = ToolboxHelper.GetTextureCopy(splatmap);
                        m_Splatmaps[i] = textureCopy;
                        m_SplatmapHasCopy.Add(textureCopy);
                    }
                }
                // clean up the hashset
                m_SplatmapHasCopy.Clear();
                foreach (var splatmap in m_Splatmaps)
                {
                    if (splatmap != null)
                    {
                        m_SplatmapHasCopy.Add(splatmap);
                    }
                }
            }

            //Splatmap Preview and Adjustment
            EditorStyles.label.fontStyle = FontStyle.Bold;
            EditorGUI.BeginChangeCheck();
            m_ShowSplatmapPreview = EditorGUILayout.Toggle(Styles.PreviewSplatMapTogg, m_ShowSplatmapPreview);
            if (EditorGUI.EndChangeCheck())
            {
                m_PreviewIsDirty = true;
                if (m_ShowSplatmapPreview)
                {
                    GetAndSetActiveRenderPipelineSettings();
                }
            }
            EditorStyles.label.fontStyle = FontStyle.Normal;

            ++EditorGUI.indentLevel;
            m_Settings.AdjustAllSplats = EditorGUILayout.Toggle(Styles.MultiAdjustTogg, m_Settings.AdjustAllSplats);

            EditorGUILayout.BeginHorizontal();
            m_Settings.RotationAdjust = (UtilitySettings.RotationAdjustment)EditorGUILayout.EnumPopup(Styles.RotateSplatmapLabel, m_Settings.RotationAdjust);
            if (GUILayout.Button(Styles.RotateSplatmapBtn, GUILayout.Width(150)))
            {
                RotateSplatmap();
            }
            EditorGUILayout.EndHorizontal();

            EditorGUILayout.BeginHorizontal();
            m_Settings.FlipAdjust = (UtilitySettings.FlipAdjustment)EditorGUILayout.EnumPopup(Styles.FlipSplatmapLabel, m_Settings.FlipAdjust);
            if (GUILayout.Button(Styles.FlipSplatmapBtn, GUILayout.Width(150)))
            {
                FlipSplatmap();
            }
            EditorGUILayout.EndHorizontal();

            --EditorGUI.indentLevel;
            EditorGUILayout.EndVertical();

            EditorGUILayout.BeginHorizontal();
            EditorGUILayout.Space();

            if (GUILayout.Button(Styles.ExportToTerrSplatmapBtn, GUILayout.Height(Styles.ButtonHeight), GUILayout.Width(Styles.ButtonWidth)))
            {
                ExportSplatmapsToTerrain();
            }
            if (GUILayout.Button(Styles.ResetSplatmapsBtn, GUILayout.Height(Styles.ButtonHeight), GUILayout.Width(Styles.ButtonWidth)))
            {
                ResetSplatmaps();
            }

            EditorGUILayout.EndHorizontal();

            if (m_PreviewIsDirty)
            {
                if (!m_ShowSplatmapPreview)
                {
                    RevertPreviewMaterial();
                }
                else if (ValidatePreviewTexture())
                {
                    m_PreviewMaterial.DisableKeyword("_HEATMAP");
                    m_PreviewMaterial.EnableKeyword("_SPLATMAP_PREVIEW");
                    UpdateAdjustedSplatmaps();
                }
                m_PreviewIsDirty = false;
            }
        }

        bool OnCanAddSplatmapElement(ReorderableList list)
        {
            return list.count < m_MaxSplatmapCount;
        }

        void OnAddSplatmapElement(ReorderableList list)
        {
            Texture2D newSplatmap = null;
            m_Splatmaps.Add(newSplatmap);
            m_SplatmapList.index = m_Splatmaps.Count - 1;
        }

        void OnRemoveSplatmapElement(ReorderableList list)
        {
            m_Splatmaps.RemoveAt(list.index);
            list.index = 0;
            m_SelectedSplatMap = 0;
            if (list.count == 0)
            {
                RevertPreviewMaterial();
            }
        }

        void OnSelectSplatmapElement(ReorderableList list)
        {
            m_SelectedSplatMap = list.index;
            m_PreviewIsDirty = true;
        }

        const int kSplatmapElementHeight = 64;
        const int kSplatmapLabelWidth = 100;
        const int kSplatmapFieldWidth = 75;
        void DrawSplatmapElement(Rect rect, int index, bool selected, bool focused)
        {
            rect.height = rect.height + kElementPadding;
            var rectLabel = new Rect(rect.x, rect.y, kSplatmapLabelWidth, kSplatmapElementHeight);
            var rectObject = new Rect((rectLabel.x + kSplatmapLabelWidth), rect.y + kElementPadding, kSplatmapFieldWidth, kSplatmapElementHeight);
            if (m_Splatmaps.Count > 0)
            {
                // label is the built-in splatmap name that gets auto assigned
                string label = "SplatAlpha " + index;
                EditorGUI.LabelField(rectLabel, label);
                m_Splatmaps[index] = EditorGUI.ObjectField(rectObject, m_Splatmaps[index], typeof(Texture2D), false) as Texture2D;
            }
        }

        void ShowReplaceSplatmapGUI()
        {
            // Replace Splatmap
            EditorGUI.BeginChangeCheck();
            m_Settings.SplatmapTerrain = EditorGUILayout.ObjectField(Styles.TerrainToReplaceSplatmap, m_Settings.SplatmapTerrain, typeof(Terrain), true) as Terrain;
            if (EditorGUI.EndChangeCheck())
            {
                if (m_Settings.SplatmapTerrain != null)
                {
                    TerrainData terrainData = m_Settings.SplatmapTerrain.terrainData;
                    if (terrainData.alphamapTextureCount == 1)
                    {
                        m_Settings.SplatmapOld0 = terrainData.alphamapTextures[0];
                        m_Settings.SplatmapOld1 = null;
                    }
                    if (terrainData.alphamapTextureCount == 2)
                    {
                        m_Settings.SplatmapOld0 = terrainData.alphamapTextures[0];
                        m_Settings.SplatmapOld1 = terrainData.alphamapTextures[1];
                    }
                    m_SplatmapResolution = terrainData.alphamapResolution;
                }
                else
                {
                    m_Settings.SplatmapOld0 = null;
                    m_Settings.SplatmapOld1 = null;
                    m_SplatmapResolution = 0;
                }
            }
            EditorGUILayout.Separator();
            EditorGUILayout.BeginHorizontal();
            EditorGUILayout.LabelField(Styles.SplatmapResolution.text + m_SplatmapResolution.ToString());
            EditorGUILayout.EndHorizontal();
            EditorGUILayout.BeginHorizontal();
            m_Settings.SplatmapOld0 = EditorGUILayout.ObjectField(Styles.SplatAlpha0, m_Settings.SplatmapOld0, typeof(Texture2D), false) as Texture2D;
            m_Settings.SplatmapNew0 = EditorGUILayout.ObjectField(Styles.SplatAlpha0New, m_Settings.SplatmapNew0, typeof(Texture2D), false) as Texture2D;
            EditorGUILayout.EndHorizontal();
            EditorGUILayout.BeginHorizontal();
            m_Settings.SplatmapOld1 = EditorGUILayout.ObjectField(Styles.SplatAlpha1, m_Settings.SplatmapOld1, typeof(Texture2D), false) as Texture2D;
            m_Settings.SplatmapNew1 = EditorGUILayout.ObjectField(Styles.SplatAlpha1New, m_Settings.SplatmapNew1, typeof(Texture2D), false) as Texture2D;
            EditorGUILayout.EndHorizontal();
            EditorGUILayout.BeginHorizontal();
            EditorGUILayout.Space();
            if (GUILayout.Button(Styles.ReplaceSplatmapsBtn, GUILayout.Height(Styles.ButtonHeight), GUILayout.Width(Styles.ButtonWidth)))
            {
                ReplaceSplatmaps();
            }
            if (GUILayout.Button(Styles.ResetSplatmapsBtn, GUILayout.Height(Styles.ButtonHeight), GUILayout.Width(Styles.ButtonWidth)))
            {
                ResetSplatmaps();
            }
            EditorGUILayout.EndHorizontal();
        }

        void ShowExportSplatmapGUI()
        {
            // Export Splatmaps
            EditorGUILayout.BeginHorizontal();
            m_Settings.SplatFolderPath = EditorGUILayout.TextField(Styles.ExportSplatmapFolderPath, m_Settings.SplatFolderPath);
            if (GUILayout.Button("...", GUILayout.Width(25)))
            {
                // clear the keyboard focus so we can update the value
                GUIUtility.keyboardControl = -1;

                var newSplatmapPath = EditorUtility.OpenFolderPanel("Select a folder...", m_Settings.SplatFolderPath, "");
                // confirm that the user didn't cancel
                if (newSplatmapPath != "")
                {
                    m_Settings.SplatFolderPath = newSplatmapPath;
                }
            }
            EditorGUILayout.EndHorizontal();

            if (m_Settings.SplatFolderPath == "")
            {
                EditorGUILayout.HelpBox("Empty folder path. Be sure to assign a folder path before exporting.", MessageType.Warning);
            }

            m_Settings.SelectedFormat = (UtilitySettings.ImageFormat)EditorGUILayout.EnumPopup(Styles.ExportSplatmapFormat, m_Settings.SelectedFormat);
            EditorGUILayout.BeginHorizontal();
            EditorGUILayout.Space();
            if (GUILayout.Button(Styles.ExportSplatmapsBtn, GUILayout.Height(Styles.ButtonHeight), GUILayout.Width(Styles.ButtonWidth)))
            {
                var selectedTerrains = Selection.GetFiltered(typeof(Terrain), SelectionMode.Unfiltered);
                ExportSplatmaps(selectedTerrains);
            }
            EditorGUILayout.EndHorizontal();
        }

        void ShowExportHeightmapGUI()
        {
            EditorGUILayout.BeginHorizontal();
            m_Settings.HeightmapFolderPath = EditorGUILayout.TextField(Styles.ExportHeightmapFolderPath, m_Settings.HeightmapFolderPath);
            if (GUILayout.Button("...", GUILayout.Width(25)))
            {
                // clear the keyboard focus so we can update the value
                GUIUtility.keyboardControl = -1;

                var newHeightmapPath = EditorUtility.OpenFolderPanel("Select a folder...", m_Settings.HeightmapFolderPath, "");
                // handle if the user pressed cancel
                if (newHeightmapPath != "")
                {
                    m_Settings.HeightmapFolderPath = newHeightmapPath;
                }

            }
            EditorGUILayout.EndHorizontal();

            if (m_Settings.HeightmapFolderPath == "")
            {
                EditorGUILayout.HelpBox("Empty folder path. Be sure to assign a folder path before exporting.", MessageType.Warning);
            }

            //EditorGUILayout.LabelField("Heightmap Format: .raw");
            //EditorGUILayout.BeginHorizontal();
            //m_SelectedDepth = EditorGUILayout.Popup(Styles.HeightmapBitDepth, m_SelectedDepth, m_DepthOptions.Keys.ToArray());
            //EditorGUILayout.EndHorizontal();
            //EditorGUILayout.BeginHorizontal();
            //m_Settings.HeightmapByteOrder = (ToolboxHelper.ByteOrder)EditorGUILayout.EnumPopup(Styles.HeightmapByteOrder, m_Settings.HeightmapByteOrder);
            //EditorGUILayout.EndHorizontal();

            //Future to support PNG and TGA. 
            m_Settings.HeightFormat = (Heightmap.Format)EditorGUILayout.EnumPopup(Styles.HeightmapSelectedFormat, m_Settings.HeightFormat);
            if (m_Settings.HeightFormat == Heightmap.Format.RAW)
            {
                EditorGUILayout.BeginHorizontal();
                m_Settings.HeightmapDepth = (Heightmap.Depth)EditorGUILayout.EnumPopup(Styles.HeightmapBitDepth, m_Settings.HeightmapDepth);
                EditorGUILayout.EndHorizontal();
                EditorGUILayout.BeginHorizontal();
                m_Settings.HeightmapByteOrder = (ToolboxHelper.ByteOrder)EditorGUILayout.EnumPopup(Styles.HeightmapByteOrder, m_Settings.HeightmapByteOrder);
                EditorGUILayout.EndHorizontal();
            }
            EditorGUILayout.BeginHorizontal();
            EditorGUILayout.MinMaxSlider(Styles.HeightmapRemap, ref m_Settings.ExportHeightRemapMin, ref m_Settings.ExportHeightRemapMax, 0f, 1.0f);
            EditorGUILayout.LabelField(Styles.HeightmapRemapMin, GUILayout.Width(40.0f));
            m_Settings.ExportHeightRemapMin = EditorGUILayout.FloatField(m_Settings.ExportHeightRemapMin, GUILayout.Width(75.0f));
            EditorGUILayout.LabelField(Styles.HeightmapRemapMax, GUILayout.Width(40.0f));
            m_Settings.ExportHeightRemapMax = EditorGUILayout.FloatField(m_Settings.ExportHeightRemapMax, GUILayout.Width(75.0f));
            EditorGUILayout.EndHorizontal();
            m_Settings.FlipVertically = EditorGUILayout.Toggle(Styles.FlipVertically, m_Settings.FlipVertically);
            EditorGUILayout.BeginHorizontal();
            EditorGUILayout.Space();
            if (GUILayout.Button(Styles.ExportHeightmapsBtn, GUILayout.Height(Styles.ButtonHeight), GUILayout.Width(Styles.ButtonWidth)))
            {
                var selectedTerrains = Selection.GetFiltered(typeof(Terrain), SelectionMode.Unfiltered);
                ExportHeightmaps(selectedTerrains);
            }
            EditorGUILayout.EndHorizontal();
            EditorGUILayout.Separator();
        }

        void ShowHeightRemapGUI()
        {
            EditorGUILayout.LabelField(Styles.RemapLabel, EditorStyles.boldLabel);

            // ---- remap section 
            ++EditorGUI.indentLevel;
            EditorGUILayout.BeginHorizontal();

            // min-max fields 
            EditorGUILayout.BeginVertical(GUILayout.ExpandWidth(true));
            EditorGUILayout.BeginHorizontal();
            EditorGUILayout.LabelField("Heightmap lower boundary");
            m_Settings.LowerBound = EditorGUILayout.IntField(m_Settings.LowerBound);
            EditorGUILayout.EndHorizontal();

            EditorGUILayout.BeginHorizontal();
            EditorGUILayout.LabelField("Heightmap upper boundary");
            m_Settings.UpperBound = EditorGUILayout.IntField(m_Settings.UpperBound);
            EditorGUILayout.EndHorizontal();
            EditorGUILayout.EndVertical();
            // end min-max fields

            // button line
            EditorGUILayout.BeginHorizontal();
            EditorGUILayout.Space();
            if (GUILayout.Button(Styles.RemapButtonLabel, GUILayout.Width(Styles.ButtonWidth), GUILayout.Height(36)))
            {
                OptimizeHeightRange.RemapSelectedTerrains(m_Settings.LowerBound, m_Settings.UpperBound);
            }

            EditorGUILayout.EndHorizontal();
            // end button line

            EditorGUILayout.EndHorizontal();
            --EditorGUI.indentLevel;
            // ----  end remap section 

            EditorGUILayout.Separator();
            EditorGUILayout.Separator();

            // ---- optimize section
            EditorGUILayout.LabelField(Styles.OptimizeLabel, EditorStyles.boldLabel);
            ++EditorGUI.indentLevel;
            EditorGUILayout.BeginHorizontal();

            // padding fields
            EditorGUILayout.BeginVertical();
            EditorGUILayout.BeginHorizontal();
            EditorGUILayout.LabelField("Lower boundary padding");
            m_Settings.BottomPad = Mathf.Clamp(EditorGUILayout.FloatField(m_Settings.BottomPad), 0, 1f);
            EditorGUILayout.EndHorizontal();

            EditorGUILayout.BeginHorizontal();
            EditorGUILayout.LabelField("Upper boundary padding");
            m_Settings.TopPad = Mathf.Clamp(EditorGUILayout.FloatField(m_Settings.TopPad), 0, 1f);
            EditorGUILayout.EndHorizontal();
            EditorGUILayout.EndVertical();
            // end padding fields

            EditorGUILayout.Space();
            if (GUILayout.Button(Styles.OptimizeButtonLabel, GUILayout.Width(Styles.ButtonWidth), GUILayout.Height(36)))
            {
                OptimizeHeightRange.OptimizeSelectedTerrains(m_Settings.BottomPad, m_Settings.TopPad);
            }

            EditorGUILayout.EndHorizontal();
            --EditorGUI.indentLevel;
            // ---- end optimize section

            EditorGUILayout.Separator();
        }

        void UpdateAdjustedSplatmaps()
        {
            List<Terrain> terrains = m_Terrains.ToList();
            if (terrains.Count == 0)
            {
                EditorUtility.DisplayDialog("Error", "Select a terrain before previewing the splatmap.", "OK");
                RevertPreviewMaterial();
                return;
            }

            List<Terrain> sortedTerrains = terrains.OrderBy(t => t.gameObject.transform.position.x).ThenBy(t => t.gameObject.transform.position.z).ToList();

            Texture2D splatMap = m_Splatmaps[m_SelectedSplatMap];
            Vector2Int tileOffset = Vector2Int.zero;
            int tilesX = terrains.Select(t => t.gameObject.transform.position.x).Distinct().Count();
            int tilesZ = terrains.Select(t => t.gameObject.transform.position.z).Distinct().Count();
            int expectedCount = tilesX * tilesZ;
            int tilesCount = terrains.Count;
            int index = 0;

            Vector2Int resolution = new Vector2Int(splatMap.width / tilesX, splatMap.height / tilesZ);
            Texture2D texture = new Texture2D(resolution.x, resolution.y);

            if (!ValidateSplatmap(terrains, resolution, expectedCount, tilesCount))
            {
                RevertPreviewMaterial();
                return;
            }

            for (int x = 0; x < tilesX; x++, tileOffset.x += resolution.x)
            {
                tileOffset.y = 0;
                for (int y = 0; y < tilesZ; y++, tileOffset.y += resolution.y)
                {
                    texture = new Texture2D(resolution.x, resolution.y);
                    var newPixels = splatMap.GetPixels(tileOffset.x, tileOffset.y, resolution.x, resolution.y);
#if UNITY_2019_2_OR_NEWER
#else
                    sortedTerrains[index].materialType = Terrain.MaterialType.Custom;
#endif
                    sortedTerrains[index].materialTemplate = m_PreviewMaterial;
                    texture.SetPixels(newPixels);
                    texture.Apply();

                    m_PreviewMaterialPropBlock.Clear();
                    m_PreviewMaterialPropBlock.SetTexture("_SplatmapTex", texture);
                    sortedTerrains[index].SetSplatMaterialPropertyBlock(m_PreviewMaterialPropBlock);
                    index++;
                }
            }

        }

        void DrawLayerIcon(Texture icon, int index)
        {
            if (icon == null)
                return;

            int width = icon.width;
            Rect position = new Rect(0, width * index, width, width);
            int size = Mathf.Min((int)position.width, (int)position.height);
            if (size >= icon.width * 2)
                size = icon.width * 2;

            FilterMode filterMode = icon.filterMode;
            icon.filterMode = FilterMode.Point;
            EditorGUILayout.BeginVertical("Box", GUILayout.Width(140));
            GUILayout.Label(icon);

            if (m_PaletteLayers[index] != null && m_PaletteLayers[index].AssignedLayer != null)
            {
                GUILayout.BeginHorizontal();
                GUILayout.Label(m_PaletteLayers[index].AssignedLayer.name, GUILayout.Width(90));
                GUILayout.EndHorizontal();
            }

            EditorGUILayout.EndVertical();
            icon.filterMode = filterMode;
        }

        public void AddLayersToSelectedTerrains(bool clearExistingLayers)
        {
            Terrain[] terrains;
            if (m_Settings.ApplyAllTerrains)
            {
                terrains = ToolboxHelper.GetAllTerrainsInScene();
            }
            else
            {
                terrains = ToolboxHelper.GetSelectedTerrainsInScene();
            }

            if (terrains == null || terrains.Length == 0)
            {
                EditorUtility.DisplayDialog("Warning", "No selected terrain found. Please select to continue.", "OK");
                return;
            }

            int index = 0;
            if (terrains.Length > 0 && m_PaletteLayers.Count > 0)
            {
                foreach (var terrain in terrains)
                {
                    if (!terrain || !terrain.terrainData)
                    {
                        continue;
                    }

                    EditorUtility.DisplayProgressBar("Applying terrain layers", string.Format("Updating terrain tile ({0})", terrain.name), ((float)index / (terrains.Count())));
                    m_LayersAlreadyAdded = TerrainToolboxLayer.AddLayersToTerrain(terrain.terrainData, m_PaletteLayers.Select(l => l.AssignedLayer).ToList(), clearExistingLayers);

                    index++;
                }

                AssetDatabase.SaveAssets();
                EditorUtility.ClearProgressBar();
            }
            else
            {
                m_LayersAlreadyAdded = false;
            }
        }

        void RemoveLayersFromSelectedTerrains()
        {
            Terrain[] terrains;
            if (m_Settings.ApplyAllTerrains)
            {
                terrains = ToolboxHelper.GetAllTerrainsInScene();
            }
            else
            {
                terrains = ToolboxHelper.GetSelectedTerrainsInScene();
            }

            if (terrains == null || terrains.Length == 0)
            {
                EditorUtility.DisplayDialog("Warning", "No selected terrain found. Please select to continue.", "OK");
                return;
            }

            if (EditorUtility.DisplayDialog("Confirm", "Are you sure you want to remove all existing layers from terrain(s)?", "Continue", "Cancel"))
            {
                int index = 0;
                if (terrains.Length > 0)
                {
                    foreach (var terrain in terrains)
                    {
                        EditorUtility.DisplayProgressBar("Removing terrain layers", string.Format("Updating terrain tile ({0})", terrain.name), ((float)index / (terrains.Count())));
                        if (!terrain || !terrain.terrainData)
                        {
                            continue;
                        }

                        var layers = terrain.terrainData.terrainLayers;
                        if (layers == null || layers.Length == 0)
                        {
                            continue;
                        }

                        TerrainToolboxLayer.RemoveAllLayers(terrain.terrainData);
                        index++;
                    }

                    AssetDatabase.SaveAssets();
                    EditorUtility.ClearProgressBar();
                }
            }
        }


        public void ImportLayersFromTerrain()
        {
            m_Terrains = ToolboxHelper.GetSelectedTerrainsInScene();
            if (m_Terrains.Length != 1)
            {
                EditorUtility.DisplayDialog("Warning", "Layers can only be imported from 1 terrain.", "OK");
            }
            else
            {
                Terrain terrain = m_Terrains[0];
                m_PaletteLayers.Clear();
                m_CopiedLayers.Clear();
                foreach (TerrainLayer layer in terrain.terrainData.terrainLayers)
                {
                    Layer paletteLayer = new Layer();
                    paletteLayer.AssignedLayer = layer;
                    m_PaletteLayers.Add(paletteLayer);
                }
                m_CopiedLayers.AddRange(terrain.terrainData.terrainLayers);
            }
        }

        internal void ImportSplatmapsFromTerrain(bool bypassDisplays = false)
        {
            m_Terrains = ToolboxHelper.GetSelectedTerrainsInScene();
            if (m_Terrains.Length != 1)
            {
                if (!bypassDisplays)
                    EditorUtility.DisplayDialog("Warning", "Splatmaps can only be imported from 1 terrain.", "OK");
            }
            else
            {
                Terrain terrain = m_Terrains[0];
                m_Splatmaps.Clear();
                foreach (Texture2D alphamap in terrain.terrainData.alphamapTextures)
                {
                    var textureCopy = ToolboxHelper.GetTextureCopy(alphamap);
                    m_SplatmapHasCopy.Add(textureCopy);
                    m_Splatmaps.Add(textureCopy);
                }

                UpdateCachedTerrainMaterials();
            }
        }

        void DuplicateTerrains()
        {
            m_Terrains = ToolboxHelper.GetSelectedTerrainsInScene(SelectionMode.TopLevel);

            if (m_Terrains == null || m_Terrains.Length == 0)
            {
                EditorUtility.DisplayDialog("Error", "No terrain(s) selected. Please select and try again.", "OK");
                return;
            }

            foreach (var rootTerrain in m_Terrains)
            {
                // Duplicate the root terrain object, which will also duplicate any child objects.
                GameObject newGO = UnityEngine.Object.Instantiate(rootTerrain.gameObject);

                // Make sure the clone matches Unity Editor naming preferences for duplicates.
                newGO.name = rootTerrain.gameObject.name;
                GameObjectUtility.EnsureUniqueNameForSibling(newGO);

                // Find every child with a terrain and duplicate the terrain data.
                foreach(var terrain in newGO.GetComponentsInChildren<Terrain>())
                {
                    var dataPath = AssetDatabase.GetAssetPath(terrain.terrainData);
                    var dataPathNew = AssetDatabase.GenerateUniqueAssetPath(dataPath);
                    AssetDatabase.CopyAsset(dataPath, dataPathNew);
                    TerrainData terrainData = AssetDatabase.LoadAssetAtPath<TerrainData>(dataPathNew);
                    terrain.GetComponent<Terrain>().terrainData = terrainData;

                    // Update terrain data reference in terrain collider.
                    TerrainCollider collider = terrain.gameObject.GetComponent<TerrainCollider>();
                    collider.terrainData = terrainData;
                }
                Undo.RegisterCreatedObjectUndo(newGO, "Duplicate terrain");
            }
            AssetDatabase.SaveAssets();
            AssetDatabase.Refresh();
        }

        internal void RemoveTerrains(bool isTest = false)
        {
            m_Terrains = ToolboxHelper.GetSelectedTerrainsInScene();

            if (!isTest && m_Terrains == null || m_Terrains.Length == 0)
            {
                EditorUtility.DisplayDialog("Error", "No terrain components selected. Please select and try again.", "OK");
                return;
            }

            if (isTest || EditorUtility.DisplayDialog("Confirm", $"Are you sure you want to delete the selected terrain components and their data assets? This process cannot be undone.", "Continue", "Cancel"))
            {
                foreach (var terrain in m_Terrains)
                {
                    if (terrain.terrainData)
                    {
                        var path = AssetDatabase.GetAssetPath(terrain.terrainData);
                        AssetDatabase.MoveAssetToTrash(path);
                    }

                    // If the gameobject only has terrain components and no children, delete the whole thing.
                    // Otherwise, only delete the terrain components.
                    int numComponents = terrain.gameObject.GetComponents<Component>().Select(x => x.GetType())
                        .Count(x => x != typeof(Terrain) && x != typeof(TerrainCollider) && x != typeof(Transform));
                    if (numComponents == 0 && terrain.transform.childCount == 0)
                    {
                        UnityEngine.Object.DestroyImmediate(terrain.gameObject);
                    }
                    else
                    {
                        var collider = terrain.GetComponent<TerrainCollider>();
                        UnityEngine.Object.DestroyImmediate(terrain);
                        if (collider != null)
                        {
                            UnityEngine.Object.DestroyImmediate(collider);
                        }
                    }
                }

                AssetDatabase.Refresh();
            }
        }

        bool MultipleIDExist(List<Terrain> terrains)
        {
            int[] ids = terrains.Select(t => t.groupingID).ToArray();
            if (ids.Distinct().ToArray().Length > 1)
            {
                return true;
            }
            else
            {
                return false;
            }
        }

        internal void SplitTerrains(bool isTest = false)
        {
            var terrainsFrom = ToolboxHelper.GetSelectedTerrainsInScene();

            if (terrainsFrom == null || terrainsFrom.Length == 0)
            {
                EditorUtility.DisplayDialog("Error", "No terrain(s) selected. Please select and try again.", "OK");
                return;
            }

            // check if multiple grouping ids selected
            if (MultipleIDExist(terrainsFrom.ToList()))
            {
                EditorUtility.DisplayDialog("Error", "The terrains selected have inconsistent Grouping IDs.", "OK");
                return;
            }

            int new_id = GetGroupIDForSplittedNewTerrain(terrainsFrom);

            try
            {
                foreach (var terrain in terrainsFrom)
                {
                    SplitTerrain(terrain, new_id, isTest);
                }
            }
            finally
            {
                AssetDatabase.SaveAssets();
                AssetDatabase.Refresh();
                EditorUtility.ClearProgressBar();
            }
        }

        internal void SplitTerrain(Terrain terrain, int new_id, bool isTest = false)
        {
            if (m_Settings.TileSplit <= 1)
            {
                m_Settings.TileSplit = 2;
                if (!isTest)
                {
                    EditorUtility.DisplayDialog("Warning", "Invalid split value. Resetting to 2.", "OK");
                    return;
                }
            }

            TerrainData terrainData = terrain.terrainData;
            Vector3 startPosition = terrain.transform.position;
            float tileWidth = terrainData.size.x / m_Settings.TileSplit;
            float tileLength = terrainData.size.z / m_Settings.TileSplit;
            float tileHeight = terrainData.size.y;
            Vector2Int heightOffset = Vector2Int.zero;
            Vector2Int detailOffset = Vector2Int.zero;
            Vector2Int controlOffset = Vector2Int.zero;
            Vector3 tilePosition = terrain.transform.position;

            // get parent gameobject (the original terrain if it's not under a terrain group, otherwise the terrain group)
            GameObject parentGO = terrain.gameObject;
            if (terrain.transform.parent != null && terrain.transform.parent.gameObject != null)
            {
                var parent = terrain.transform.parent.gameObject;
                var groupComp = parent.GetComponent<TerrainGroup>();
                if (parent != null && groupComp != null)
                {
                    parentGO = parent;
                }
            }

            int originalHeightmapRes = terrainData.heightmapResolution;
            int newHeightmapRes = (originalHeightmapRes - 1) / m_Settings.TileSplit;
            int newDetailmapRes = terrainData.detailResolution / m_Settings.TileSplit;

            if (!ToolboxHelper.IsPowerOfTwo(newHeightmapRes))
            {
                EditorUtility.DisplayDialog("Error", "Heightmap resolution of new tiles is not power of 2 with current settings.", "OK");
                return;
            }

            if (newHeightmapRes < k_MinHeightmapRes)
            {
                if (!isTest && !EditorUtility.DisplayDialog("Warning",
                    $"The heightmap resolution of the newly split tiles is {newHeightmapRes + 1}; " +
                    $"this is smaller than the minimum supported value of {k_MinHeightmapRes + 1}.\n\n" +
                    $"Would you like to split terrain into {m_Settings.TileSplit}x{m_Settings.TileSplit} " +
                    $"tiles of heightmap resolution {k_MinHeightmapRes + 1}?",
                    "OK",
                    "Cancel"))
                {
                    return;
                }

                ToolboxHelper.ResizeHeightmap(terrainData, k_MinHeightmapRes * m_Settings.TileSplit);
                newHeightmapRes = k_MinHeightmapRes;
            }

            // control map resolution
            int newControlRes = terrainData.alphamapResolution / m_Settings.TileSplit;
            if (!ToolboxHelper.IsPowerOfTwo(newControlRes))
            {
                EditorUtility.DisplayDialog("Error", "Splat control map resolution of new tiles is not power of 2 with current settings.", "OK");
                return;
            }

            int tileIndex = 0;
            int tileCount = m_Settings.TileSplit * m_Settings.TileSplit;
            Terrain[] terrainsNew = new Terrain[tileCount];
#if UNITY_2019_3_OR_NEWER

            // holes render texture
            RenderTexture rt = RenderTexture.GetTemporary(terrainData.holesTexture.width, terrainData.holesTexture.height);
            Graphics.Blit(terrainData.holesTexture, rt);
            rt.filterMode = FilterMode.Point;
#endif

            for (int x = 0; x < m_Settings.TileSplit; x++, heightOffset.x += newHeightmapRes, detailOffset.x += newDetailmapRes, controlOffset.x += newControlRes, tilePosition.x += tileWidth)
            {
                heightOffset.y = 0;
                detailOffset.y = 0;
                controlOffset.y = 0;
                tilePosition.z = startPosition.z;

                for (int y = 0; y < m_Settings.TileSplit; y++, heightOffset.y += newHeightmapRes, detailOffset.y += newDetailmapRes, controlOffset.y += newControlRes, tilePosition.z += tileLength)
                {
                    EditorUtility.DisplayProgressBar("Creating terrains", string.Format("Updating terrain tile ({0}, {1})", x, y), ((float)tileIndex / tileCount));

                    TerrainData terrainDataNew = new TerrainData();
                    GameObject newGO = Terrain.CreateTerrainGameObject(terrainDataNew);
                    Terrain newTerrain = newGO.GetComponent<Terrain>();

                    Guid newGuid = Guid.NewGuid();
                    string terrainName = $"Terrain_{x}_{y}_{newGuid}";
                    newGO.name = terrainName;
                    newTerrain.transform.position = tilePosition;
                    newTerrain.groupingID = new_id;
                    newTerrain.allowAutoConnect = true;
                    newTerrain.drawInstanced = terrain.drawInstanced;
                    newTerrain.transform.SetParent(parentGO.transform);

                    // get and set heights
                    terrainDataNew.heightmapResolution = newHeightmapRes + 1;
                    var heightData = terrainData.GetHeights(heightOffset.x, heightOffset.y, (newHeightmapRes + 1), (newHeightmapRes + 1));
                    terrainDataNew.SetHeights(0, 0, heightData);
                    terrainDataNew.size = new Vector3(tileWidth, tileHeight, tileLength);

                    string assetPath = $"{m_Settings.TerrainAssetDir}/{terrainName}.asset";
                    if (!Directory.Exists(m_Settings.TerrainAssetDir))
                    {
                        Directory.CreateDirectory(m_Settings.TerrainAssetDir);
                    }

                    AssetDatabase.CreateAsset(terrainDataNew, assetPath);

                    // note that add layers and alphamap operations need to happen after terrain data asset being created, so cached splat 0 and 1 data gets cleared to avoid bumping to splat 2 map.
                    // get and set terrain layers
                    TerrainToolboxLayer.AddLayersToTerrain(terrainDataNew, terrainData.terrainLayers.ToList(), true);

                    // get and set alphamaps
                    float[,,] alphamap = terrainData.GetAlphamaps(controlOffset.x, controlOffset.y, newControlRes, newControlRes);
                    terrainDataNew.alphamapResolution = newControlRes;
                    terrainDataNew.SetAlphamaps(0, 0, alphamap);

                    // get and set detailmap
                    int newDetailPatch = Mathf.Max(k_MinDetailResPerPatch, terrainData.detailResolutionPerPatch / m_Settings.TileSplit);
                    terrainDataNew.SetDetailResolution(newDetailmapRes, newDetailPatch);
                    terrainDataNew.detailPrototypes = terrainData.detailPrototypes;

                    for (int i = 0; i < terrainDataNew.detailPrototypes.Length; i++)
                    {
                        int[,] detailLayer = terrainData.GetDetailLayer(detailOffset.x, detailOffset.y, newDetailmapRes, newDetailmapRes, i);
                        terrainDataNew.SetDetailLayer(0, 0, i, detailLayer);
                    }

                    // get and set treemap
                    float treeOffsetXMin = x / (float)m_Settings.TileSplit;
                    float treeOffsetZMin = y / (float)m_Settings.TileSplit;
                    float treeOffsetXMAX = treeOffsetXMin + (1 / (float)m_Settings.TileSplit);
                    float treeOffsetZMAX = treeOffsetZMin + (1 / (float)m_Settings.TileSplit);
                    terrainDataNew.treePrototypes = terrainData.treePrototypes;
                    List<TreeInstance> treeInstances = new List<TreeInstance>();
                    TreeInstance[] treeData = terrainData.treeInstances;
                    for (int i = 0; i < treeData.Length; i++)
                    {
                        TreeInstance tree = treeData[i];
                        if (treeOffsetXMin <= tree.position.x && tree.position.x <= treeOffsetXMAX &&
                          treeOffsetZMin <= tree.position.z && tree.position.z <= treeOffsetZMAX)
                        {
                            tree.position.x = (tree.position.x - treeOffsetXMin) * m_Settings.TileSplit;
                            tree.position.z = (tree.position.z - treeOffsetZMin) * m_Settings.TileSplit;
                            treeInstances.Add(tree);
                        }
                    }
                    terrainDataNew.SetTreeInstances(treeInstances.ToArray(), true);

#if UNITY_2019_3_OR_NEWER
                    // get and set holes, however there's currently a bug in GetHoles() so using render texture blit instead
                    //var holes = terrainData.GetHoles(heightOffset.x, heightOffset.y, newHeightmapRes, newHeightmapRes);
                    //terrainDataNew.SetHoles(0, 0, holes);							
                    float divX = 1f / m_Settings.TileSplit;
                    float divZ = 1f / m_Settings.TileSplit;
                    Vector2 scale = new Vector2(divX, divZ);
                    Vector2 offset = new Vector2(divX * x, divZ * y);
                    Graphics.Blit(rt, (RenderTexture)terrainDataNew.holesTexture, scale, offset);
                    terrainDataNew.DirtyTextureRegion(TerrainData.HolesTextureName, new RectInt(0, 0, terrainDataNew.holesTexture.width, terrainDataNew.holesTexture.height), false);
#endif
                    // update other terrain settings
                    if (m_Settings.AutoUpdateSettings)
                    {
                        ApplySettingsFromSourceToTargetTerrain(terrain, newTerrain);
                    }

                    terrainsNew[tileIndex] = newTerrain;
                    tileIndex++;

                    Undo.RegisterCreatedObjectUndo(newGO, "Split terrain");
                }
            }

            m_SplitTerrains = terrainsNew;
            ToolboxHelper.CalculateAdjacencies(m_SplitTerrains, m_Settings.TileSplit, m_Settings.TileSplit);
#if UNITY_2019_3_OR_NEWER
            RenderTexture.ReleaseTemporary(rt);
#endif
            if (terrainData.heightmapResolution != originalHeightmapRes)
            {
                ToolboxHelper.ResizeHeightmap(terrainData, originalHeightmapRes);
            }
            
            // Remove terrain components from the root gameobject.
            var terrainCollider = terrain.GetComponent<TerrainCollider>();
            if (terrainCollider != null)
            {
                Undo.DestroyObjectImmediate(terrainCollider);
            }
            Undo.DestroyObjectImmediate(terrain);
        }

        int GetGroupIDForSplittedNewTerrain(Terrain[] exclude_terrains)
        {
            // check all other terrains in scene to see if group ID exists
            Terrain[] all_terrains = ToolboxHelper.GetAllTerrainsInScene();
            Terrain[] remaining_terrains = all_terrains.Except(exclude_terrains).ToArray();
            List<int> ids = new List<int>();
            int original_id = exclude_terrains[0].groupingID;
            ids.Add(original_id);
            bool exist = false;
            foreach (var terrain in remaining_terrains)
            {
                if (terrain.groupingID == original_id)
                {
                    exist = true;
                }

                ids.Add(terrain.groupingID);
            }
            List<int> unique_ids = ids.Distinct().ToList();
            int max_id = unique_ids.Max();

            // if found id exist in scene, give a new id with largest id + 1, otherwise use original terrain's id
            if (exist)
            {
                return max_id + 1;
            }
            else
            {
                return original_id;
            }
        }

        void ApplySettingsFromSourceToTargetTerrain(Terrain sourceTerrain, Terrain targetTerrain)
        {
            targetTerrain.allowAutoConnect = sourceTerrain.allowAutoConnect;
            targetTerrain.drawHeightmap = sourceTerrain.drawHeightmap;
            targetTerrain.drawInstanced = sourceTerrain.drawInstanced;
            targetTerrain.heightmapPixelError = sourceTerrain.heightmapPixelError;
            targetTerrain.basemapDistance = sourceTerrain.basemapDistance;
            targetTerrain.shadowCastingMode = sourceTerrain.shadowCastingMode;
            targetTerrain.materialTemplate = sourceTerrain.materialTemplate;
            targetTerrain.reflectionProbeUsage = sourceTerrain.reflectionProbeUsage;
#if UNITY_2019_2_OR_NEWER
#else
            targetTerrain.materialType = sourceTerrain.materialType;			
            targetTerrain.legacySpecular = sourceTerrain.legacySpecular;
            targetTerrain.legacyShininess = sourceTerrain.legacyShininess;
#endif
            targetTerrain.terrainData.baseMapResolution = sourceTerrain.terrainData.baseMapResolution;

            targetTerrain.drawTreesAndFoliage = sourceTerrain.drawTreesAndFoliage;
            targetTerrain.bakeLightProbesForTrees = sourceTerrain.bakeLightProbesForTrees;
            targetTerrain.deringLightProbesForTrees = sourceTerrain.deringLightProbesForTrees;
            targetTerrain.preserveTreePrototypeLayers = sourceTerrain.preserveTreePrototypeLayers;
            targetTerrain.detailObjectDistance = sourceTerrain.detailObjectDistance;
            targetTerrain.collectDetailPatches = sourceTerrain.collectDetailPatches;
            targetTerrain.detailObjectDensity = sourceTerrain.detailObjectDistance;
            targetTerrain.treeDistance = sourceTerrain.treeDistance;
            targetTerrain.treeBillboardDistance = sourceTerrain.treeBillboardDistance;
            targetTerrain.treeCrossFadeLength = sourceTerrain.treeCrossFadeLength;
            targetTerrain.treeMaximumFullLODCount = sourceTerrain.treeMaximumFullLODCount;

            targetTerrain.terrainData.wavingGrassStrength = sourceTerrain.terrainData.wavingGrassStrength;
            targetTerrain.terrainData.wavingGrassSpeed = sourceTerrain.terrainData.wavingGrassSpeed;
            targetTerrain.terrainData.wavingGrassAmount = sourceTerrain.terrainData.wavingGrassAmount;
            targetTerrain.terrainData.wavingGrassTint = sourceTerrain.terrainData.wavingGrassTint;

            targetTerrain.lightmapIndex = sourceTerrain.lightmapIndex;
            targetTerrain.renderingLayerMask = sourceTerrain.renderingLayerMask;
            targetTerrain.lightmapScaleOffset = sourceTerrain.lightmapScaleOffset;
            targetTerrain.realtimeLightmapIndex = sourceTerrain.realtimeLightmapIndex;
            targetTerrain.realtimeLightmapScaleOffset = sourceTerrain.realtimeLightmapScaleOffset;
            targetTerrain.editorRenderFlags = sourceTerrain.editorRenderFlags;
        }

        void ReplaceSplatmaps()
        {
            if (m_Settings.SplatmapNew0 == null && m_Settings.SplatmapNew1 == null)
            {
                if (EditorUtility.DisplayDialog("Confirm", "You don't have new splatmaps assigned. Would you like to reset splatmaps to defaults on selected terrain?", "OK", "Cancel"))
                {
                    // reset splatmaps
                    ResetSplatmapsOnTerrain(m_Settings.SplatmapTerrain);
                    return;
                }
                return;
            }

            if (m_Settings.SplatmapOld0 != null && m_Settings.SplatmapNew0 != null)
            {
                ReplaceSplatmapTexture(m_Settings.SplatmapOld0, m_Settings.SplatmapNew0);
            }

            if (m_Settings.SplatmapOld1 != null && m_Settings.SplatmapNew1 != null)
            {
                ReplaceSplatmapTexture(m_Settings.SplatmapOld1, m_Settings.SplatmapNew1);
            }

            AssetDatabase.SaveAssets();
        }

        void ReplaceSplatmapTexture(Texture2D oldTexture, Texture2D newTexture)
        {
            if (newTexture.width != newTexture.height)
            {
                EditorUtility.DisplayDialog("Error", "Could not replace splatmap. Non-square sized splatmap found.", "OK");
                return;
            }

            var undoObjects = new List<UnityEngine.Object>();
            undoObjects.Add(m_Settings.SplatmapTerrain.terrainData);
            undoObjects.AddRange(m_Settings.SplatmapTerrain.terrainData.alphamapTextures);
            Undo.RegisterCompleteObjectUndo(undoObjects.ToArray(), "Replace splatmaps");

            // set new texture to be readable through Import Settings, so we can use GetPixels() later
            if (!newTexture.isReadable)
            {
                var newPath = AssetDatabase.GetAssetPath(newTexture);
                var newImporter = AssetImporter.GetAtPath(newPath) as TextureImporter;
                if (newImporter != null)
                {
                    newImporter.isReadable = true;
                    AssetDatabase.ImportAsset(newPath);
                    AssetDatabase.Refresh();
                }
            }

            if (newTexture.width != oldTexture.width)
            {
                if (EditorUtility.DisplayDialog("Confirm", "Mismatched splatmap resolution found.", "Use New Resolution", "Use Old Resolution"))
                {
                    // resize to new texture size
                    oldTexture.Reinitialize(newTexture.width, newTexture.height, oldTexture.format, true);
                    // update splatmap resolution on terrain settings as well
                    m_Settings.SplatmapTerrain.terrainData.alphamapResolution = newTexture.width;
                    m_SplatmapResolution = newTexture.width;
                }
                else
                {
                    // resize to old texture size
                    newTexture.Reinitialize(oldTexture.width, oldTexture.height, newTexture.format, true);
                }
            }

            var pixelsNew = newTexture.GetPixels();
            oldTexture.SetPixels(pixelsNew);
            oldTexture.Apply();
        }

        internal void ExportSplatmapsToTerrain(bool bypassDisplays = false)
        {
            // validate settings
            // all splatmaps same resolution
            // terrains same control map resolution

            // get selected tiles and sort by position along X and Z
            List<Terrain> terrains = ToolboxHelper.GetSelectedTerrainsInScene().ToList();
            List<Terrain> sortedTerrains = terrains.OrderBy(t => t.gameObject.transform.position.x).ThenBy(t => t.gameObject.transform.position.z).ToList();

            var undoObjects = new List<UnityEngine.Object>();
            foreach (var terrain in terrains)
            {
                undoObjects.Add(terrain.terrainData);
                undoObjects.AddRange(terrain.terrainData.alphamapTextures);
            }
            Undo.RegisterCompleteObjectUndo(undoObjects.ToArray(), "Reset terrains");

            int tilesX = terrains.Select(t => t.gameObject.transform.position.x).Distinct().Count();
            int tilesZ = terrains.Select(t => t.gameObject.transform.position.z).Distinct().Count();
            int expectedCount = tilesX * tilesZ;
            if (expectedCount == 0)
            {
                if (!bypassDisplays)
                {
                    EditorUtility.DisplayDialog("Error", "No terrain(s) selected. Please select terrain tile(s) to continue.", "OK");
                }
                return;
            }

            int tilesCount = terrains.Count;
            Vector2Int tileOffset = Vector2Int.zero;
            int index = 0;

            try
            {
                for (int z = 0; z < m_Splatmaps.Count; z++)
                {
                    index = 0;
                    tileOffset = Vector2Int.zero;

                    if (m_Splatmaps[z] != null)
                    {
                        Vector2Int resolution = new Vector2Int(m_Splatmaps[z].width / tilesX, m_Splatmaps[z].height / tilesZ);
                        if (ValidateSplatmap(terrains, resolution, expectedCount, tilesCount))
                        {
                            RenderTexture oldRT = RenderTexture.active;
                            RenderTexture[] rts = new RenderTexture[m_Splatmaps.Count];
                            rts[z] = RenderTexture.GetTemporary(resolution.x, resolution.x, 0, SystemInfo.GetGraphicsFormat(UnityEngine.Experimental.Rendering.DefaultFormat.HDR));
                            Graphics.Blit(m_Splatmaps[z], rts[z]);
                            RenderTexture.active = rts[z];

                            for (int x = 0; x < tilesX; x++, tileOffset.x += resolution.x)
                            {
                                tileOffset.y = 0;
                                for (int y = 0; y < tilesZ; y++, tileOffset.y += resolution.y)
                                {
                                    if (!bypassDisplays)
                                    {
                                        EditorUtility.DisplayProgressBar("Applying splatmaps", string.Format("Updating terrain tile {0}", sortedTerrains[index].name), ((float)index / tilesCount));
                                    }

                                    ToolboxHelper.ResizeControlTexture(sortedTerrains[index].terrainData, resolution.x);
                                    if (sortedTerrains[index].terrainData.alphamapTextures[z] != null)
                                    {
                                        ToolboxHelper.CopyActiveRenderTextureToTexture(sortedTerrains[index].terrainData.alphamapTextures[z], new RectInt(tileOffset.x, tileOffset.y, resolution.x, resolution.x), Vector2Int.zero, false);
                                    }

                                    index++;
                                }
                            }

                            RenderTexture.active = oldRT;
                            for (int i = 0; i < m_Splatmaps.Count; i++)
                            {
                                RenderTexture.ReleaseTemporary(rts[i]);
                            }
                        }
                    }
                }
            }
            finally
            {
                AssetDatabase.SaveAssets();
                AssetDatabase.Refresh();
                EditorUtility.ClearProgressBar();
            }
        }

        bool ValidateSplatmap(List<Terrain> terrains, Vector2Int resolution, int expectedCount, int tilesCount)
        {
            foreach (Terrain terrain in terrains)
            {
                if (terrain.terrainData.alphamapTextures.Length < m_SplatmapList.count)
                {
                    EditorUtility.DisplayDialog("Error", "You've selected more splatmaps to import than each terrain can hold. Either select less splatmaps or add more to your terrain.", "OK"); //string.Format("The selected amount of {0} splatmap textures, dosen't match that of the average splatmaps of {1:0.##} per terrain ", m_SplatmapList.count, averageSplatmaps)
                    return false;
                }
            }

            if (!ToolboxHelper.IsPowerOfTwo(resolution.x))
            {
                EditorUtility.DisplayDialog("Error", "The selected splatmap resolutions aren't a power of two.", "OK");
                return false;
            }
            else if (resolution.x != resolution.y)
            {
                EditorUtility.DisplayDialog("Error", "The selected splatmaps resolution isn't square.", "OK");
                return false;
            }
            else if (expectedCount > tilesCount)
            {
                EditorUtility.DisplayDialog("Error", "The terrains selected aren't square.", "OK");
                return false;
            }
            return true;
        }

        bool ValidatePreviewTexture()
        {
            if (m_Splatmaps.Count == 0)
            {
                EditorUtility.DisplayDialog("Error", "Add and select a splatmap before previewing the splatmap.", "OK");
                RevertPreviewMaterial();
                return false;
            }
            else if (m_Splatmaps[m_SelectedSplatMap] == null)
            {
                EditorUtility.DisplayDialog("Error", "Select a splatmap before previewing the splatmap.", "OK");

                if (m_Splatmaps[0] == null)
                {
                    RevertPreviewMaterial();
                    return false;
                }
                m_SelectedSplatMap = 0;
            }

            Texture2D texture = m_Splatmaps[m_SelectedSplatMap];
            TextureFormat format = texture.format;
            if ((format != TextureFormat.RGBA32 && format != TextureFormat.ARGB32 && format != TextureFormat.RGB24) || !texture.isReadable)
            {
                EditorUtility.DisplayDialog("Error", "The Texture format isn't compatable. Please change it to either RGBA32, ARGB32, or RGB24 and enable Read/Write.", "OK");
                RevertPreviewMaterial();
                return false;
            }

            return true;
        }

        void ResetSplatmaps()
        {
            var terrains = ToolboxHelper.GetSelectedTerrainsInScene();
            int index = 0;
            foreach (var terrain in terrains)
            {
                EditorUtility.DisplayProgressBar("Resetting Splatmaps", string.Format("Resetting splatmaps on terrain {0}", terrain.name), (index / (terrains.Count())));
                ResetSplatmapsOnTerrain(terrain);
                index++;
            }
            EditorUtility.ClearProgressBar();
        }

        void ResetSplatmapsOnTerrain(Terrain terrain)
        {
            TerrainData terrainData = terrain.terrainData;
            if (terrainData.alphamapTextureCount < 1)
                return;

            var undoObjects = new List<UnityEngine.Object>();
            undoObjects.Add(terrainData);
            undoObjects.AddRange(terrainData.alphamapTextures);
            Undo.RegisterCompleteObjectUndo(undoObjects.ToArray(), "Reset splatmaps");

            Color splatDefault = new Color(1, 0, 0, 0); // red
            Color splatZero = new Color(0, 0, 0, 0);

            var pixelsFirst = terrainData.alphamapTextures[0].GetPixels();
            for (int p = 0; p < pixelsFirst.Length; p++)
            {
                pixelsFirst[p] = splatDefault;
            }
            terrainData.alphamapTextures[0].SetPixels(pixelsFirst);
            terrainData.alphamapTextures[0].Apply();

            for (int i = 1; i < terrainData.alphamapTextureCount; i++)
            {
                var pixels = terrainData.alphamapTextures[i].GetPixels();
                for (int j = 0; j < pixels.Length; j++)
                {
                    pixels[j] = splatZero;
                }
                terrainData.alphamapTextures[i].SetPixels(pixels);
                terrainData.alphamapTextures[i].Apply();
            }

            AssetDatabase.SaveAssets();
            AssetDatabase.Refresh();
        }

        void ExportSplatmaps(UnityEngine.Object[] terrains)
        {
            if (terrains == null || terrains.Length == 0)
            {
                EditorUtility.DisplayDialog("Error", "No terrain(s) selected. Please select terrain tile(s) to continue.", "OK");
                return;
            }

            if (m_Settings.SplatFolderPath == "")
            {
                EditorUtility.DisplayDialog("Error", "Empty export folder path. Please assign a path and try again.", "OK");
                return;
            }

            if (!Directory.Exists(m_Settings.SplatFolderPath))
            {
                Directory.CreateDirectory(m_Settings.SplatFolderPath);
            }

            var fileExtension = m_Settings.SelectedFormat == UtilitySettings.ImageFormat.TGA ? ".tga" : ".png";
            int index = 0;

            foreach (var t in terrains)
            {
                var terrain = t as Terrain;
                EditorUtility.DisplayProgressBar("Exporting Splatmaps", string.Format("Exporting splatmaps on terrain {0}", terrain.name), (index / (terrains.Count())));
                TerrainData data = terrain.terrainData;
                for (var i = 0; i < data.alphamapTextureCount; i++)
                {
                    Texture2D tex = data.alphamapTextures[i];
                    byte[] bytes;
                    if (m_Settings.SelectedFormat == UtilitySettings.ImageFormat.TGA)
                    {
                        bytes = tex.EncodeToTGA();
                    }
                    else
                    {
                        bytes = tex.EncodeToPNG();
                    }
                    string filename = terrain.name + "_splatmap_" + i + fileExtension;
                    File.WriteAllBytes($"{m_Settings.SplatFolderPath}/{filename}", bytes);
                }

                index++;
            }

            AssetDatabase.SaveAssets();
            AssetDatabase.Refresh();
            EditorUtility.ClearProgressBar();
        }

        internal void ExportHeightmaps(UnityEngine.Object[] terrains)
        {
            if (terrains == null || terrains.Length == 0)
            {
                EditorUtility.DisplayDialog("Error", "No terrain(s) selected. Please select terrain tile(s) to continue.", "OK");
                return;
            }

            if (m_Settings.HeightmapFolderPath == "")
            {
                EditorUtility.DisplayDialog("Error", "Empty export folder path. Please assign a path and try again.", "OK");
                return;
            }

            if (!Directory.Exists(m_Settings.HeightmapFolderPath))
            {
                Directory.CreateDirectory(m_Settings.HeightmapFolderPath);
            }

            int index = 0;

            foreach (var t in terrains)
            {
                var terrain = t as Terrain;
                EditorUtility.DisplayProgressBar("Exporting Heightmaps", string.Format("Exporting heightmap on terrain {0}", terrain.name), (index / (terrains.Count())));
                TerrainData terrainData = terrain.terrainData;
                string fileName = terrain.name + "_heightmap";
                string path = Path.Combine(m_Settings.HeightmapFolderPath, fileName);

                switch (m_Settings.HeightFormat)
                {
                    case Heightmap.Format.RAW:
                        ToolboxHelper.ExportTerrainHeightsToRawFile(terrainData, path, m_Settings.HeightmapDepth, m_Settings.FlipVertically, m_Settings.HeightmapByteOrder, new Vector2(m_Settings.ExportHeightRemapMin, m_Settings.ExportHeightRemapMax));
                        break;
                    default:
                        ToolboxHelper.ExportTerrainHeightsToTexture(terrainData, m_Settings.HeightFormat, path, m_Settings.FlipVertically, new Vector2(m_Settings.ExportHeightRemapMin, m_Settings.ExportHeightRemapMax));
                        break;
                }

                index++;
            }

            AssetDatabase.SaveAssets();
            AssetDatabase.Refresh();
            EditorUtility.ClearProgressBar();
        }

        internal void RotateSplatmap()
        {
            if (!ValidatePreviewTexture())
                return;

            if (m_Settings.AdjustAllSplats)
            {
                for (int i = 0; i < m_SplatmapList.count; i++)
                {
                    RotateTexture(m_Splatmaps[i]);
                }
            }
            else
            {
                RotateTexture(m_Splatmaps[m_SelectedSplatMap]);
            }

            if (m_ShowSplatmapPreview)
                m_PreviewIsDirty = true;
        }

        void RotateTexture(Texture2D texture)
        {
            Undo.RegisterCompleteObjectUndo(texture, "Rotate Texture");
            Color32[] originalPixels;
            Color32[] rotatedPixels;
            originalPixels = texture.GetPixels32();
            rotatedPixels = new Color32[originalPixels.Length];
            //bool clockwise = m_Settings.RotationAdjust == UtilitySettings.RotationAdjustment.Clockwise ? true : false;

            int width = texture.width;
            int height = texture.height;
            int rotatedIndex, originalIndex;
            for (int row = 0; row < height; row++)
            {
                for (int col = 0; col < width; col++)
                {
                    rotatedIndex = (col + 1) * height - row - 1;
                    if (m_Settings.RotationAdjust == UtilitySettings.RotationAdjustment.Clockwise)
                    {
                        originalIndex = originalPixels.Length - 1 - (row * width + col);
                    }
                    else
                    {
                        originalIndex = row * width + col;
                    }
                    //originalIndex = clockwise ? originalPixels.Length - 1 - (row * width + col) : row * width + col;

                    rotatedPixels[rotatedIndex] = originalPixels[originalIndex];
                }
            }
            texture.SetPixels32(rotatedPixels);
            texture.Apply();
        }

        internal void FlipSplatmap()
        {
            if (!ValidatePreviewTexture())
                return;

            bool horizontal = m_Settings.FlipAdjust == UtilitySettings.FlipAdjustment.Horizontal ? true : false;

            if (m_Settings.AdjustAllSplats)
            {
                for (int i = 0; i < m_SplatmapList.count; i++)
                {
                    ToolboxHelper.FlipTexture(m_Splatmaps[i], horizontal);
                }
            }
            else
            {
                ToolboxHelper.FlipTexture(m_Splatmaps[m_SelectedSplatMap], horizontal);
            }

            if (m_ShowSplatmapPreview)
                m_PreviewIsDirty = true;
        }

        void FlipTexture(Texture2D texture)
        {
            Undo.RegisterCompleteObjectUndo(texture, "Flip Texture");
            Color32[] originalPixels;
            Color32[] flippedPixels;
            bool horizontal = m_Settings.FlipAdjust == UtilitySettings.FlipAdjustment.Horizontal ? true : false;
            int difference;
            int width;
            int height;

            int flippedIndex, originalIndex;

            originalPixels = texture.GetPixels32();
            flippedPixels = new Color32[originalPixels.Length];
            width = texture.width;
            height = texture.height;
            difference = width - height;
            for (int row = 0; row < height; row++)
            {
                for (int col = 0; col < width; col++)
                {
                    flippedIndex = horizontal ? (((width - 1) - row) * height + col) - difference : (height - 1) + (row * width) - col - difference;
                    originalIndex = row * width + col;
                    if (flippedIndex < 0)
                        continue;
                    flippedPixels[flippedIndex] = originalPixels[originalIndex];
                }
            }
            texture.SetPixels32(flippedPixels);
            texture.Apply();
        }

        internal void RevertPreviewMaterial()
        {
            if (m_PreviewMaterial == null)
            {
                GetAndSetActiveRenderPipelineSettings();
            }
            m_PreviewMaterial.DisableKeyword("_SPLATMAP_PREVIEW");
            for (int i = 0; i < m_Terrains.Length; i++)
            {
                if (m_Terrains[i] != null)
                {
#if UNITY_2019_2_OR_NEWER
                    m_Terrains[i].materialTemplate = m_TerrainMaterials[i];
#else
                    m_Terrains[i].materialType = m_TerrainMaterialType;
                    if (m_TerrainMaterialType == Terrain.MaterialType.Custom)
                    {
                        m_Terrains[i].materialTemplate = m_TerrainMaterials[i];
                    }
                    else if (m_TerrainMaterialType == Terrain.MaterialType.BuiltInLegacySpecular)
                    {
                        m_Terrains[i].legacyShininess = m_TerrainLegacyShininess;
                        m_Terrains[i].legacySpecular = m_TerrainLegacySpecular;
                        m_Terrains[i].materialTemplate = null;
                    }
                    else
                    {
                        m_Terrains[i].materialTemplate = null;
                    }
#endif
                }
            }
            m_ShowSplatmapPreview = false;
        }

        void GetAndSetActiveRenderPipelineSettings()
        {
            m_Terrains = ToolboxHelper.GetSelectedTerrainsInScene();
            UpdateCachedTerrainMaterials();

            ToolboxHelper.RenderPipeline currentPipeline = ToolboxHelper.GetRenderPipeline();
            if (m_ActiveRenderPipeline == currentPipeline)
                return;

            m_ActiveRenderPipeline = currentPipeline;
            Shader vizShader = Shader.Find("Hidden/Builtin_TerrainVisualization");
            switch (m_ActiveRenderPipeline)
            {
                case ToolboxHelper.RenderPipeline.HD:
                    m_MaxLayerCount = k_MaxLayerHD;
                    m_MaxSplatmapCount = k_MaxSplatmapHD;
                    vizShader = Shader.Find("Hidden/HDRP_TerrainVisualization");
                    break;
                case ToolboxHelper.RenderPipeline.LW:
                    // this is a temp setting, in LW if height based blending or opacity as density enabled, 
                    // we only support 4 layers and 1 splatmap
                    // this will get checked when applying changes to each terrain
                    // To-do: update max allowance check once LW terrain checked in
                    m_MaxLayerCount = k_MaxNoLimit;
                    m_MaxSplatmapCount = k_MaxNoLimit;
                    vizShader = Shader.Find("Hidden/LWRP_TerrainVisualization");
                    break;
                case ToolboxHelper.RenderPipeline.Universal:
                    m_MaxLayerCount = k_MaxNoLimit;
                    m_MaxSplatmapCount = k_MaxNoLimit;
                    vizShader = Shader.Find("Hidden/Universal_TerrainVisualization");
                    break;
                default:
                    m_MaxLayerCount = k_MaxNoLimit;
                    m_MaxSplatmapCount = k_MaxNoLimit;
                    if (m_Terrains == null || m_Terrains.Length == 0)
                    {
                        break;
                    }
#if UNITY_2019_2_OR_NEWER
#else
                    m_TerrainMaterialType = m_Terrains[0].materialType;
                    if (m_TerrainMaterialType == Terrain.MaterialType.BuiltInLegacySpecular)
                    {
                        m_TerrainLegacyShininess = m_Terrains[0].legacyShininess;
                        m_TerrainLegacySpecular = m_Terrains[0].legacySpecular;
                    }
#endif
                    break;
            }
            m_PreviewMaterial = TerrainToolboxVisualization.GetVizMaterial(vizShader);
        }

        /// <summary>
        /// Updates an array of materials used to revert the selected terrain material from
        /// the preview material back to its original Terrain material.
        /// </summary>
        void UpdateCachedTerrainMaterials()
        {
            m_TerrainMaterials.Clear();

            foreach (Terrain terrain in m_Terrains)
            {
                m_TerrainMaterials.Add(terrain.materialTemplate);
            }
        }

        void CreateNewPalette()
        {
            string filePath = EditorUtility.SaveFilePanelInProject("Create New Palette", "New Layer Palette.asset", "asset", "");
            if (string.IsNullOrEmpty(filePath))
            {
                return;
            }
            m_SelectedLayerPalette = null;
            var newPalette = ScriptableObject.CreateInstance<TerrainPalette>();
            foreach (var layer in m_PaletteLayers)
            {
                newPalette.PaletteLayers.Add(layer.AssignedLayer);
            }
            AssetDatabase.CreateAsset(newPalette, filePath);
            m_SelectedLayerPalette = newPalette;

            AssetDatabase.SaveAssets();
            AssetDatabase.Refresh();
        }

        void LoadPalette()
        {
            if (!GetPalette())
                return;

            m_PaletteLayers.Clear();
            foreach (var layer in m_SelectedLayerPalette.PaletteLayers)
            {
                Layer newLayer = new Layer();
                newLayer.AssignedLayer = layer;
                newLayer.IsSelected = true;
                m_PaletteLayers.Add(newLayer);
            }
        }

        bool GetPalette()
        {
            if (m_SelectedLayerPalette == null)
            {
                if (EditorUtility.DisplayDialog("Error", "No layer palette found, create a new one?", "OK", "Cancel"))
                {
                    CreateNewPalette();
                    return true;
                }
                else
                {
                    return false;
                }
            }

            return true;
        }

        public void SaveSettings()
        {
            if (m_SelectedLayerPalette != null)
            {
                m_Settings.PalettePath = AssetDatabase.GetAssetPath(m_SelectedLayerPalette);
            }
            else
            {
                m_Settings.PalettePath = string.Empty;
            }

            string filePath = ToolboxHelper.GetPrefFilePath(ToolboxHelper.ToolboxPrefsUtility);
            string utilitySettings = JsonUtility.ToJson(m_Settings);
            File.WriteAllText(filePath, utilitySettings);
            RevertPreviewMaterial();
            SceneView.RepaintAll();
        }

        public void LoadSettings()
        {
            string filePath = ToolboxHelper.GetPrefFilePath(ToolboxHelper.ToolboxPrefsUtility);
            if (File.Exists(filePath))
            {
                string utilitySettingsData = File.ReadAllText(filePath);
                JsonUtility.FromJsonOverwrite(utilitySettingsData, m_Settings);
            }

            if (m_Settings.PalettePath == string.Empty)
            {
                m_SelectedLayerPalette = null;
            }
            else
            {
                m_SelectedLayerPalette = AssetDatabase.LoadAssetAtPath(m_Settings.PalettePath, typeof(TerrainPalette)) as TerrainPalette;
            }

            GetAndSetActiveRenderPipelineSettings();
            EditorSceneManager.sceneSaving += OnSceneSaving;
            EditorSceneManager.sceneOpened += OnSceneOpened;
            EditorApplication.playModeStateChanged += OnPlayModeChanged;
        }

        public void OnLostFocus()
        {
            if (!m_ShowSplatmapPreview)
                return;

            string mouseOverWindow;
            try
            {
                mouseOverWindow = EditorWindow.mouseOverWindow.ToString();
            }
            catch
            {
                mouseOverWindow = null;
            }

            if (mouseOverWindow == null
                || mouseOverWindow != " (UnityEditor.TerrainTools.TerrainToolboxWindow)"
                && mouseOverWindow != " (UnityEditor.SceneView)")
            {
                RevertPreviewMaterial();
            }
        }

        void OnSceneSaving(UnityEngine.SceneManagement.Scene scene, string path)
        {
            if (m_ShowSplatmapPreview)
            {
                RevertPreviewMaterial();
            }
        }

        void OnSceneOpened(UnityEngine.SceneManagement.Scene scene, OpenSceneMode open)
        {
            m_PaletteLayers.Clear();
        }

        void OnPlayModeChanged(PlayModeStateChange state)
        {
            RevertPreviewMaterial();
        }
    }
}