diff --git a/OpenRA.Game/Traits/CreatesShroud.cs b/OpenRA.Game/Traits/CreatesShroud.cs
index 8d087251c4..c5729fad33 100644
--- a/OpenRA.Game/Traits/CreatesShroud.cs
+++ b/OpenRA.Game/Traits/CreatesShroud.cs
@@ -32,6 +32,13 @@ namespace OpenRA.Traits
 			lobbyShroudFogDisabled = !self.World.LobbyInfo.GlobalSettings.Shroud && !self.World.LobbyInfo.GlobalSettings.Fog;
 		}
 
+		CPos[] ShroudedTiles(Actor self)
+		{
+			return Shroud.GetVisOrigins(self)
+				.SelectMany(o => Shroud.FindVisibleTiles(self.World, o, Range))
+				.Distinct().ToArray();
+		}
+
 		public void Tick(Actor self)
 		{
 			if (lobbyShroudFogDisabled)
@@ -43,20 +50,20 @@ namespace OpenRA.Traits
 				cachedLocation = self.Location;
 				cachedDisabled = disabled;
 
-				CPos[] shrouded = null;
+				var shrouded = ShroudedTiles(self);
 				foreach (var p in self.World.Players)
 				{
 					p.Shroud.RemoveShroudGeneration(self);
-					p.Shroud.AddShroudGeneration(self, ref shrouded);
+					p.Shroud.AddShroudGeneration(self, shrouded);
 				}
 			}
 		}
 
 		public void AddedToWorld(Actor self)
 		{
-			CPos[] shrouded = null;
+			var shrouded = ShroudedTiles(self);
 			foreach (var p in self.World.Players)
-				p.Shroud.AddShroudGeneration(self, ref shrouded);
+				p.Shroud.AddShroudGeneration(self, shrouded);
 		}
 
 		public void RemovedFromWorld(Actor self)
diff --git a/OpenRA.Game/Traits/RevealsShroud.cs b/OpenRA.Game/Traits/RevealsShroud.cs
index adb1dc459f..f10bbedb10 100644
--- a/OpenRA.Game/Traits/RevealsShroud.cs
+++ b/OpenRA.Game/Traits/RevealsShroud.cs
@@ -31,6 +31,13 @@ namespace OpenRA.Traits
 			lobbyShroudFogDisabled = !self.World.LobbyInfo.GlobalSettings.Shroud && !self.World.LobbyInfo.GlobalSettings.Fog;
 		}
 
+		CPos[] VisibleTiles(Actor self)
+		{
+			return Shroud.GetVisOrigins(self)
+				.SelectMany(o => Shroud.FindVisibleTiles(self.World, o, Range))
+				.Distinct().ToArray();
+		}
+
 		public void Tick(Actor self)
 		{
 			if (lobbyShroudFogDisabled)
@@ -40,20 +47,20 @@ namespace OpenRA.Traits
 			{
 				cachedLocation = self.Location;
 
-				CPos[] visible = null;
+				var visible = VisibleTiles(self);
 				foreach (var p in self.World.Players)
 				{
 					p.Shroud.RemoveVisibility(self);
-					p.Shroud.AddVisibility(self, ref visible);
+					p.Shroud.AddVisibility(self, visible);
 				}
 			}
 		}
 
 		public void AddedToWorld(Actor self)
 		{
-			CPos[] visible = null;
+			var visible = VisibleTiles(self);
 			foreach (var p in self.World.Players)
-				p.Shroud.AddVisibility(self, ref visible);
+				p.Shroud.AddVisibility(self, visible);
 		}
 
 		public void RemovedFromWorld(Actor self)
diff --git a/OpenRA.Game/Traits/World/Shroud.cs b/OpenRA.Game/Traits/World/Shroud.cs
index 462f8d39fa..4ced59c1ca 100644
--- a/OpenRA.Game/Traits/World/Shroud.cs
+++ b/OpenRA.Game/Traits/World/Shroud.cs
@@ -77,7 +77,7 @@ namespace OpenRA.Traits
 			return GetVisOrigins(actor).SelectMany(o => FindVisibleTiles(actor.World, o, range)).Distinct().ToArray();
 		}
 
-		static IEnumerable<CPos> FindVisibleTiles(World world, CPos position, WRange radius)
+		public static IEnumerable<CPos> FindVisibleTiles(World world, CPos position, WRange radius)
 		{
 			var map = world.Map;
 			var r = (radius.Range + 1023) / 1024;
@@ -89,15 +89,11 @@ namespace OpenRA.Traits
 					yield return cell;
 		}
 
-		public void AddVisibility(Actor a, ref CPos[] visible)
+		public void AddVisibility(Actor a, CPos[] visible)
 		{
-			var rs = a.TraitOrDefault<RevealsShroud>();
-			if (rs == null || !a.Owner.IsAlliedWith(self.Owner) || rs.Range == WRange.Zero)
+			if (!a.Owner.IsAlliedWith(self.Owner))
 				return;
 
-			// Lazily generate the visible tiles, allowing the caller to re-use them if desired.
-			visible = visible ?? FindVisibleTiles(a, rs.Range);
-
 			foreach (var c in visible)
 			{
 				var uv = c.ToMPos(map);
@@ -134,15 +130,11 @@ namespace OpenRA.Traits
 			Invalidate(visible);
 		}
 
-		public void AddShroudGeneration(Actor a, ref CPos[] shrouded)
+		public void AddShroudGeneration(Actor a, CPos[] shrouded)
 		{
-			var cs = a.TraitOrDefault<CreatesShroud>();
-			if (cs == null || a.Owner.IsAlliedWith(self.Owner) || cs.Range == WRange.Zero)
+			if (a.Owner.IsAlliedWith(self.Owner))
 				return;
 
-			// Lazily generate the shrouded tiles, allowing the caller to re-use them if desired.
-			shrouded = shrouded ?? FindVisibleTiles(a, cs.Range);
-
 			foreach (var c in shrouded)
 				generatedShroudCount[c]++;
 
@@ -177,10 +169,17 @@ namespace OpenRA.Traits
 				CPos[] shrouded = null;
 				foreach (var p in self.World.Players)
 				{
-					p.Shroud.RemoveVisibility(self);
-					p.Shroud.AddVisibility(self, ref visible);
-					p.Shroud.RemoveShroudGeneration(self);
-					p.Shroud.AddShroudGeneration(self, ref shrouded);
+					if (p.Shroud.visibility.TryGetValue(self, out visible))
+					{
+						p.Shroud.RemoveVisibility(self);
+						p.Shroud.AddVisibility(self, visible);
+					}
+
+					if (p.Shroud.generation.TryGetValue(self, out shrouded))
+					{
+						p.Shroud.RemoveShroudGeneration(self);
+						p.Shroud.AddShroudGeneration(self, shrouded);
+					}
 				}
 			}
 		}