Tweak helicopter movement / attack

OpenRA.Mods.RA/Activities/HeliFly.cs

@@ -21,6 +21,7 @@
 using System;
 using OpenRA.GameRules;
 using OpenRA.Traits;
+using System.Linq;
 
 namespace OpenRA.Mods.RA.Activities
 {
@@ -48,8 +49,16 @@ namespace OpenRA.Mods.RA.Activities
 				unit.Altitude += Math.Sign(info.CruiseAltitude - unit.Altitude);
 				return this;
 			}
-
-			var dist = Dest - self.CenterLocation;
+			
+			// Prevent multiple units from stacking together
+			var otherHelis = self.World.FindUnitsInCircle(self.CenterLocation, info.IdealSeparation)
+				.Where(a => a.traits.Contains<Helicopter>());
+			
+			var f = otherHelis
+				.Select(h => GetRepulseForce(self, h))
+				.Aggregate(float2.Zero, (a, b) => a + b);
+			
+			var dist = Dest - self.CenterLocation + f;
 			if (float2.WithinEpsilon(float2.Zero, dist, 2))
 			{
 				self.CenterLocation = Dest;
@@ -67,6 +76,19 @@ namespace OpenRA.Mods.RA.Activities
 
 			return this;
 		}
+		
+		// Todo: Duplicated from HeliAttack
+		const float Epsilon = .5f;
+		float2 GetRepulseForce(Actor self, Actor h)
+		{
+			if (self == h)
+				return float2.Zero;
+			var d = self.CenterLocation - h.CenterLocation;
+			if (d.LengthSquared < Epsilon)
+				return float2.FromAngle((float)self.World.SharedRandom.NextDouble() * 3.14f);
+
+			return (2 / d.LengthSquared) * d;
+		}
 
 		public void Cancel(Actor self) { isCanceled = true; NextActivity = null; }
 	}