better system for texture terrain.

LandblockExtraction/AtlasMaker/TerrainInfo/Terrain.cs

@@ -11,12 +11,12 @@ public class Terrain {
         subTerrains.Add(sousTerrain);
     }
 
-    public int DetermineSubTerrain(float pitch) {
+    public SubTerrain DetermineSubTerrain(float pitch) {
         foreach (var terrain in subTerrains) {
             if (terrain.MatchesPitch(pitch)) {
-                return terrain.terrainIndex;
+                return terrain;
             }
         }
-        return terrainIndex;
+        return subTerrains.First();
     }
 }