Fix overlapping tracks when vehicle rotates.

Also optimize the function slightly.

OpenRA.Mods.Common/Traits/Render/LeavesTrails.cs

@@ -10,6 +10,7 @@
 #endregion
 
 using System.Collections.Generic;
+using System.Linq;
 using OpenRA.Mods.Common.Effects;
 using OpenRA.Traits;
 
@@ -93,6 +94,10 @@ namespace OpenRA.Mods.Common.Traits.Render
 		bool wasStationary;
 		bool isMoving;
 
+		bool previouslySpawned;
+		CPos previousSpawnCell;
+		WAngle previousSpawnFacing;
+
 		void ITick.Tick(Actor self)
 		{
 			if (IsTraitDisabled)
@@ -120,18 +125,26 @@ namespace OpenRA.Mods.Common.Traits.Render
 				if (++offset >= Info.Offsets.Length)
 					offset = 0;
 
+				if (!Info.TerrainTypes.Any() || Info.TerrainTypes.Contains(type))
+				{
+					var spawnFacing = Info.SpawnAtLastPosition ? cachedFacing : facing?.Facing ?? WAngle.Zero;
+
+					if (previouslySpawned && previousSpawnCell == spawnCell)
+						spawnFacing = previousSpawnFacing;
+
 					var offsetRotation = Info.Offsets[offset].Rotate(body.QuantizeOrientation(self, self.Orientation));
 					var spawnPosition = Info.SpawnAtLastPosition ? cachedPosition : self.CenterPosition;
-
 					var pos = Info.Type == TrailType.CenterPosition ? spawnPosition + body.LocalToWorld(offsetRotation) :
 						self.World.Map.CenterOfCell(spawnCell);
 
-				var spawnFacing = Info.SpawnAtLastPosition ? cachedFacing : facing?.Facing ?? WAngle.Zero;
-
-				if (Info.TerrainTypes.Count == 0 || Info.TerrainTypes.Contains(type))
 					self.World.AddFrameEndTask(w => w.Add(new SpriteEffect(pos, spawnFacing, self.World, Info.Image,
 						Info.Sequences.Random(Game.CosmeticRandom), Info.Palette, Info.VisibleThroughFog)));
 
+					previouslySpawned = true;
+					previousSpawnCell = spawnCell;
+					previousSpawnFacing = spawnFacing;
+				}
+
 				cachedPosition = self.CenterPosition;
 				cachedFacing = facing?.Facing ?? WAngle.Zero;
 				ticks = 0;