fix units being visible under fog

OpenRA.Game/Traits/Render/HiddenUnderFog.cs

@@ -0,0 +1,30 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace OpenRA.Traits.Render
+{
+	class HiddenUnderFogInfo : ITraitInfo
+	{
+		public object Create(Actor self) { return new HiddenUnderFog(self); }
+	}
+
+	class HiddenUnderFog : IRenderModifier
+	{
+		Shroud shroud;
+
+		public HiddenUnderFog(Actor self)
+		{
+			shroud = self.World.WorldActor.traits.Get<Shroud>();
+		}
+
+		public IEnumerable<Renderable> ModifyRender(Actor self, IEnumerable<Renderable> r)
+		{
+			if (self.Owner == self.World.LocalPlayer || shroud.visibleCells[self.Location.X, self.Location.Y] > 0)
+				return r;
+
+			return new Renderable[] { };
+		}
+	}
+}