mapgen build mesh priority update

OpenKh.Command.MapGen/Models/MaterialDef.cs

@@ -118,6 +118,12 @@ public class MaterialDef
         /// </summary>
         public bool normal { get; set; } = false;
 
+        /// <summary>
+        /// Explicit build priority. Lower number = built first.
+        /// Meshes with no priority set are appended after all prioritized meshes in their original order.
+        /// </summary>
+        public int? priority { get; set; }
+
         public static MaterialDef CreateFallbackFor(string name) =>
             new MaterialDef
             {

OpenKh.Command.MapGen/Utils/MapBuilder.cs

@@ -36,6 +36,17 @@ public MapBuilder(string modelFile, MapGenConfig config, Func<MaterialDef, Imgd>
 
             var singleFaces = ConvertModelIntoFaces(modelFile, config);
 
+            // Apply explicit material priority ordering from mapdef.yml.
+            // Faces whose material has a priority set come first (ascending),
+            // followed by unprioritized faces in their original order.
+            singleFaces = singleFaces
+                .Select((face, originalIndex) => (face, originalIndex))
+                .OrderBy(x => x.face.matDef.priority.HasValue ? 0 : 1)
+                .ThenBy(x => x.face.matDef.priority ?? 0)
+                .ThenBy(x => x.originalIndex)
+                .Select(x => x.face)
+                .ToList();
+
             logger.Debug($"Loading process has done.");
 
             logger.Debug($"Starting MapBuilding.");