Only use largest blocker instead of largest actor for projectile blocker overscan

Before this, we unconditionally used the largest OuterRadius of all actors inside a mod for overscanning of blockable projectiles.
However, in many mods the only blockable actors are 1-cell walls, and even if there are gates like in TS, they usually aren't the largest actors in terms of hit-shape.

So this measure should save a bit of performance by reducing the overscan radius of blockable projectiles, especially in mods where walls are the only blocking actors.

OpenRA.Game/Traits/TraitsInterfaces.cs

@@ -259,6 +259,7 @@ namespace OpenRA.Traits
 		IEnumerable<Actor> ActorsInBox(WPos a, WPos b);
 
 		WDist LargestActorRadius { get; }
+		WDist LargestBlockingActorRadius { get; }
 	}
 
 	public interface IRenderModifier

OpenRA.Mods.Common/Traits/BlocksProjectiles.cs

@@ -41,7 +41,7 @@ namespace OpenRA.Mods.Common.Traits
 
 		public static bool AnyBlockingActorsBetween(World world, WPos start, WPos end, WDist width, out WPos hit)
 		{
-			var actors = world.FindActorsOnLine(start, end, width);
+			var actors = world.FindBlockingActorsOnLine(start, end, width);
 			var length = (end - start).Length;
 
 			foreach (var a in actors)

OpenRA.Mods.Common/Traits/World/ActorMap.cs

@@ -184,6 +184,7 @@ namespace OpenRA.Mods.Common.Traits
 		readonly Predicate<Actor> actorShouldBeRemoved;
 
 		public WDist LargestActorRadius { get; private set; }
+		public WDist LargestBlockingActorRadius { get; private set; }
 
 		public ActorMap(World world, ActorMapInfo info)
 		{
@@ -202,6 +203,8 @@ namespace OpenRA.Mods.Common.Traits
 			actorShouldBeRemoved = removeActorPosition.Contains;
 
 			LargestActorRadius = map.Rules.Actors.SelectMany(a => a.Value.TraitInfos<HitShapeInfo>()).Max(h => h.Type.OuterRadius);
+			var blockers = map.Rules.Actors.Where(a => a.Value.HasTraitInfo<IBlocksProjectilesInfo>());
+			LargestBlockingActorRadius = blockers.Any() ? blockers.SelectMany(a => a.Value.TraitInfos<HitShapeInfo>()).Max(h => h.Type.OuterRadius) : WDist.Zero;
 		}
 
 		void INotifyCreated.Created(Actor self)

OpenRA.Mods.Common/WorldExtensions.cs

@@ -26,7 +26,7 @@ namespace OpenRA.Mods.Common
 		/// <param name="lineEnd">The position the line should end at</param>
 		/// <param name="lineWidth">How close an actor's health radius needs to be to the line to be considered 'intersected' by the line</param>
 		/// <returns>A list of all the actors intersected by the line</returns>
-		public static IEnumerable<Actor> FindActorsOnLine(this World world, WPos lineStart, WPos lineEnd, WDist lineWidth)
+		public static IEnumerable<Actor> FindActorsOnLine(this World world, WPos lineStart, WPos lineEnd, WDist lineWidth, bool onlyBlockers = false)
 		{
 			// This line intersection check is done by first just finding all actors within a square that starts at the source, and ends at the target.
 			// Then we iterate over this list, and find all actors for which their health radius is at least within lineWidth of the line.
@@ -39,7 +39,8 @@ namespace OpenRA.Mods.Common
 			var yDir = yDiff < 0 ? -1 : 1;
 
 			var dir = new WVec(xDir, yDir, 0);
-			var overselect = dir * (1024 + lineWidth.Length + world.ActorMap.LargestActorRadius.Length);
+			var largestValidActorRadius = onlyBlockers ? world.ActorMap.LargestBlockingActorRadius.Length : world.ActorMap.LargestActorRadius.Length;
+			var overselect = dir * (1024 + lineWidth.Length + largestValidActorRadius);
 			var finalTarget = lineEnd + overselect;
 			var finalSource = lineStart - overselect;
 
@@ -64,6 +65,11 @@ namespace OpenRA.Mods.Common
 			return intersectedActors;
 		}
 
+		public static IEnumerable<Actor> FindBlockingActorsOnLine(this World world, WPos lineStart, WPos lineEnd, WDist lineWidth)
+		{
+			return world.FindActorsOnLine(lineStart, lineEnd, lineWidth, true);
+		}
+
 		/// <summary>
 		/// Finds all the actors of which their health radius is intersected by a specified circle.
 		/// </summary>