expose material instance

Source/Engine/UI/GUI/Special/RadialMenu.cs

@@ -129,6 +129,12 @@ namespace FlaxEngine.GUI
             }
         }
 
+        /// <summary>
+        /// The material instance of <paramref name="Material"/> used to draw the menu.
+        /// </summary>
+        [HideInEditor]
+        public MaterialInstance MaterialInstance => _materialInstance;
+
         /// <summary>
         /// The selected callback.
         /// </summary>