diff --git a/OpenRA.Game/Traits/World/BibLayer.cs b/OpenRA.Game/Traits/World/BibLayer.cs
index 3b5513af01..4feb47cfe4 100644
--- a/OpenRA.Game/Traits/World/BibLayer.cs
+++ b/OpenRA.Game/Traits/World/BibLayer.cs
@@ -12,7 +12,8 @@ using System;
 using System.Drawing;
 using System.Linq;
 using OpenRA.FileFormats;
-using OpenRA.Graphics;
+using OpenRA.Graphics;
+using System.Collections.Generic;
 
 namespace OpenRA.Traits
 {
@@ -26,9 +27,8 @@ namespace OpenRA.Traits
 	class BibLayer: IRenderOverlay, IWorldLoaded
 	{		
 		World world;
-		BibLayerInfo info;
-		
-		TileReference<byte,byte>[,] tiles;
+		BibLayerInfo info;
+		Dictionary<int2, TileReference<byte, byte>> tiles;
 		Sprite[][] bibSprites;
 		
 		public BibLayer(Actor self, BibLayerInfo info)
@@ -44,8 +44,8 @@ namespace OpenRA.Traits
 		
 		public void WorldLoaded(World w)
 		{
-			world = w;
-			tiles = new TileReference<byte,byte>[w.Map.MapSize.X,w.Map.MapSize.Y];
+			world = w;
+			tiles = new Dictionary<int2, TileReference<byte, byte>>();
 		}
 		
 		public void DoBib(Actor b, bool isAdd)
@@ -67,7 +67,7 @@ namespace OpenRA.Traits
 				byte type = (byte)((isAdd) ? bib+1 : 0);
 				byte index = (byte)i;
 				
-				tiles[p.X,p.Y] = new TileReference<byte,byte>(type,index);
+				tiles[p] = new TileReference<byte,byte>(type,index);
 			}
 		}
 
@@ -75,22 +75,17 @@ namespace OpenRA.Traits
 		{
 			var cliprect = Game.viewport.ShroudBounds().HasValue
 				? Rectangle.Intersect(Game.viewport.ShroudBounds().Value, world.Map.Bounds) : world.Map.Bounds;
-
-			var minx = cliprect.Left;
-			var maxx = cliprect.Right;
-
-			var miny = cliprect.Top;
-			var maxy = cliprect.Bottom;
-
-			for (int x = minx; x < maxx; x++)
-				for (int y = miny; y < maxy; y++)
-				{
-					var t = new int2(x, y);
-					if (world.LocalPlayer != null && !world.LocalPlayer.Shroud.IsExplored(t) || tiles[x,y].type == 0) continue;
-
-					Game.Renderer.SpriteRenderer.DrawSprite(bibSprites[tiles[x, y].type - 1][tiles[x, y].image],
-						Game.CellSize * t, "terrain");
-				}
+
+			foreach (var kv in tiles)
+			{
+				if (!cliprect.Contains(kv.Key.X, kv.Key.Y))
+					continue;
+				if (world.LocalPlayer != null && !world.LocalPlayer.Shroud.IsExplored(kv.Key))
+					continue;
+
+				Game.Renderer.SpriteRenderer.DrawSprite(bibSprites[kv.Value.type - 1][kv.Value.image],
+					Game.CellSize * kv.Key, "terrain");
+			}
 		}
 	}
 	
diff --git a/OpenRA.Game/Traits/World/SmudgeLayer.cs b/OpenRA.Game/Traits/World/SmudgeLayer.cs
index 00631a8e96..96a54e48a4 100644
--- a/OpenRA.Game/Traits/World/SmudgeLayer.cs
+++ b/OpenRA.Game/Traits/World/SmudgeLayer.cs
@@ -64,9 +64,12 @@ namespace OpenRA.Traits
 			
 			var tile = tiles[loc];
 			// Existing smudge; make it deeper
-			int depth = Info.Depths[tile.type-1];
-			if (tile.image < depth - 1)
-				tile.image++;
+			int depth = Info.Depths[tile.type-1];
+			if (tile.image < depth - 1)
+			{
+				tile.image++;
+				tiles[loc] = tile;	// struct semantics.
+			}
 		}
 		
 		public void Render()
@@ -81,7 +84,7 @@ namespace OpenRA.Traits
 				if (world.LocalPlayer != null && !world.LocalPlayer.Shroud.IsExplored(kv.Key))
 					continue;
 
-				Game.Renderer.SpriteRenderer.DrawSprite(smudgeSprites[tiles[kv.Key].type- 1][tiles[kv.Key].image],
+				Game.Renderer.SpriteRenderer.DrawSprite(smudgeSprites[kv.Value.type- 1][kv.Value.image],
 						Game.CellSize * kv.Key, "terrain");
 			}
 		}