feat: allow enabling GPU instancing directly from the material importer

Editor/Scripts/GLTFImporter.cs

@@ -98,6 +98,7 @@ private static void EnsureShadersAreLoaded()
         [SerializeField] internal bool _animationLoopTime = true;
         [SerializeField] internal bool _animationLoopPose = false;
         [SerializeField] internal bool _importMaterials = true;
+        [SerializeField] internal bool _enableGpuInstancing = false;
         [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;
         [Tooltip("Compress textures after import using the platform default settings. If you need more control, use a .gltf file instead.")]
@@ -482,6 +483,7 @@ string GetUniqueName(string desiredName)
 		                    }
 
 		                    mat.name = matName;
+		                    mat.enableInstancing = _enableGpuInstancing;
 		                    materials.Add(mat);
 	                    }
                     }

Editor/Scripts/GLTFImporterInspector.cs

@@ -163,7 +163,14 @@ private void MaterialInspectorGUI()
 			var t = target as GLTFImporter;
 			if (!t) return;
 
-			EditorGUILayout.PropertyField(serializedObject.FindProperty(nameof(GLTFImporter._importMaterials)));
+			var importMaterialsProp = serializedObject.FindProperty(nameof(GLTFImporter._importMaterials));
+			EditorGUILayout.PropertyField(importMaterialsProp);
+			if (importMaterialsProp.boolValue)
+			{
+				EditorGUI.indentLevel++;
+				EditorGUILayout.PropertyField(serializedObject.FindProperty(nameof(GLTFImporter._enableGpuInstancing)), new GUIContent("GPU Instancing"));
+				EditorGUI.indentLevel--;
+			}
 			var importedMaterials = serializedObject.FindProperty("m_Materials");
 			if (importedMaterials.arraySize > 0)
 			{