feat: import material remapping

UnityGLTF/Assets/UnityGLTF/Editor/Scripts/GLTFImporter.cs

@@ -81,6 +81,9 @@ private static void EnsureShadersAreLoaded()
         [Tooltip("Enable this to get the same main asset identifiers as glTFast uses. This is recommended for new asset imports. Note that changing this for already imported assets will break their scene references and require manually re-adding the affected assets.")]
         [SerializeField] internal bool _useSceneNameIdentifier = false;
 
+        // material remapping
+        [SerializeField] private Material[] m_Materials = new Material[0];
+
         [Serializable]
         internal class ExtensionInfo
         {
@@ -264,6 +267,7 @@ string GetUniqueName(string desiredName)
                 if (_importMaterials)
                 {
                     // Get materials
+                    var map = GetExternalObjectMap();
                     var materialHash = new HashSet<UnityEngine.Material>();
                     var materials = renderers.SelectMany(r =>
                     {
@@ -283,6 +287,20 @@ string GetUniqueName(string desiredName)
                         });
                     }).Distinct().ToArray();
 
+                    // apply material remap
+                    foreach(var r in renderers)
+                    {
+	                    // remap materials to external objects
+	                    var m = r.sharedMaterials;
+	                    for (var i = 0; i < m.Length; i++)
+	                    {
+		                    var si = new SourceAssetIdentifier(m[i]);
+		                    if (map.ContainsKey(si))
+			                    m[i] = map[si] as Material;
+	                    }
+	                    r.sharedMaterials = m;
+                    };
+
                     // Get textures
                     var textureHash = new HashSet<Texture2D>();
                     var texMaterialMap = new Dictionary<Texture2D, List<TexMaterialMap>>();
@@ -356,10 +374,17 @@ string GetUniqueName(string desiredName)
                     {
                         foreach (var mat in materials)
                         {
-                            ctx.AddObjectToAsset(GetUniqueName(mat.name), mat);
+	                        // ensure materials that are overriden aren't shown in the hierarchy.
+	                        var si = new SourceAssetIdentifier(mat);
+	                        if (map.ContainsKey(si))
+		                        mat.hideFlags = HideFlags.HideInHierarchy | HideFlags.HideInInspector;
+
+	                        ctx.AddObjectToAsset(GetUniqueName(mat.name), mat);
                         }
                     }
 
+                    m_Materials = materials;
+
 #if !UNITY_2022_1_OR_NEWER
 			        AssetDatabase.SaveAssets();
 					AssetDatabase.Refresh();
@@ -521,6 +546,13 @@ public TexMaterialMap(UnityEngine.Material material, string property, bool isNor
                 IsNormalMap = isNormalMap;
             }
         }
+
+        public override bool SupportsRemappedAssetType(Type type)
+        {
+	        if (type == typeof(Material))
+		        return true;
+	        return base.SupportsRemappedAssetType(type);
+        }
     }
 }
 #endif

UnityGLTF/Assets/UnityGLTF/Editor/Scripts/GLTFImporterInspector.cs

@@ -1,10 +1,12 @@
 #if UNITY_2017_1_OR_NEWER
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using UnityEditor;
 
 using UnityEngine;
+using Object = UnityEngine.Object;
 #if UNITY_2020_2_OR_NEWER
 using UnityEditor.AssetImporters;
 #else
@@ -72,7 +74,96 @@ public override void OnInspectorGUI()
 			}
 			EditorGUILayout.Separator();
 			EditorGUILayout.LabelField("Materials", EditorStyles.boldLabel);
+			var mats = serializedObject.FindProperty("m_Materials");
 			EditorGUILayout.PropertyField(serializedObject.FindProperty(nameof(GLTFImporter._importMaterials)));
+
+			EditorGUILayout.Separator();
+			const string key = nameof(GLTFImporterInspector) + "_RemapMaterials";
+			var newVal = EditorGUILayout.BeginFoldoutHeaderGroup(SessionState.GetBool(key, false), "Remap Materials");
+			SessionState.SetBool(key, newVal);
+			// EditorGUILayout.LabelField("Remap Materials", EditorStyles.boldLabel);
+			// extract and remap materials
+			if (newVal)
+			{
+				EditorGUI.indentLevel++;
+				var externalObjectMap = t.GetExternalObjectMap();
+
+				void ExtractMaterial(Material subAsset)
+				{
+					if (!subAsset) return;
+					var destinationPath = Path.GetDirectoryName(t.assetPath) + "/" + subAsset.name + ".mat";
+					string assetPath = AssetDatabase.GetAssetPath(subAsset);
+
+					var clone = Instantiate(subAsset);
+					AssetDatabase.CreateAsset(clone, destinationPath);
+
+					var assetImporter = AssetImporter.GetAtPath(assetPath);
+					assetImporter.AddRemap(new AssetImporter.SourceAssetIdentifier(subAsset), clone);
+
+					AssetDatabase.WriteImportSettingsIfDirty(assetPath);
+					AssetDatabase.ImportAsset(assetPath, ImportAssetOptions.ForceUpdate);
+				}
+
+				for (var i = 0; i < mats.arraySize; i++)
+				{
+					var mat = mats.GetArrayElementAtIndex(i).objectReferenceValue as Material;
+					if (!mat) continue;
+					var id = new AssetImporter.SourceAssetIdentifier(mat);
+					externalObjectMap.TryGetValue(id, out var remap);
+					EditorGUILayout.BeginHorizontal();
+					// EditorGUILayout.ObjectField(/*mat.name,*/ mat, typeof(Material), false);
+					EditorGUI.BeginChangeCheck();
+					var newObj = EditorGUILayout.ObjectField(mat.name, remap, typeof(Material), false);
+					if (EditorGUI.EndChangeCheck())
+					{
+						if (newObj)
+							t.AddRemap(id, newObj);
+						else
+							t.RemoveRemap(id);
+					}
+
+					if (!remap)
+					{
+						if (GUILayout.Button("Extract", GUILayout.Width(60)))
+							ExtractMaterial(mat);
+					}
+					else
+					{
+						if (GUILayout.Button("Restore", GUILayout.Width(60))) {
+							t.RemoveRemap(id);
+							ApplyAndImport();
+						}
+					}
+
+					EditorGUILayout.EndHorizontal();
+				}
+
+				EditorGUILayout.BeginHorizontal();
+				EditorGUILayout.PrefixLabel(" ");
+				if (GUILayout.Button("Restore Materials"))
+				{
+					for (var i = 0; i < mats.arraySize; i++)
+					{
+						var mat = mats.GetArrayElementAtIndex(i).objectReferenceValue as Material;
+						if (!mat) continue;
+						t.RemoveRemap(new AssetImporter.SourceAssetIdentifier(mat));
+					}
+				}
+
+				if (GUILayout.Button("Extract Materials"))
+				{
+					for (var i = 0; i < mats.arraySize; i++)
+					{
+						ExtractMaterial(mats.GetArrayElementAtIndex(i).objectReferenceValue as Material);
+					}
+				}
+
+				EditorGUILayout.EndHorizontal();
+				EditorGUI.indentLevel--;
+			}
+
+			EditorGUILayout.EndFoldoutHeaderGroup();
+
 			EditorGUILayout.Separator();
 
 			var identifierProp = serializedObject.FindProperty(nameof(GLTFImporter._useSceneNameIdentifier));