From 32c73fa72fccddb7e9397e1d12e898078df80903 Mon Sep 17 00:00:00 2001
From: Chris Forbes <chrisf@ijw.co.nz>
Date: Sun, 2 May 2010 13:18:13 +1200
Subject: [PATCH] heli separation

---
 OpenRA.Game/Traits/Activities/HeliAttack.cs | 36 +++++++++++++++++----
 1 file changed, 29 insertions(+), 7 deletions(-)

diff --git a/OpenRA.Game/Traits/Activities/HeliAttack.cs b/OpenRA.Game/Traits/Activities/HeliAttack.cs
index da2f24a891..6b3360cbc3 100644
--- a/OpenRA.Game/Traits/Activities/HeliAttack.cs
+++ b/OpenRA.Game/Traits/Activities/HeliAttack.cs
@@ -19,6 +19,7 @@
 #endregion
 
 using System;
+using System.Linq;
 using OpenRA.GameRules;
 
 namespace OpenRA.Traits.Activities
@@ -27,6 +28,7 @@ namespace OpenRA.Traits.Activities
 	{
 		Actor target;
 		const int CruiseAltitude = 20;
+		const int AvoidDist = 80;
 		public HeliAttack( Actor target ) { this.target = target; }
 
 		public IActivity NextActivity { get; set; }
@@ -54,17 +56,37 @@ namespace OpenRA.Traits.Activities
 			var desiredFacing = Util.GetFacing(dist, unit.Facing);
 			Util.TickFacing(ref unit.Facing, desiredFacing, self.Info.Traits.Get<UnitInfo>().ROT);
 
-			if (!float2.WithinEpsilon(float2.Zero, dist, range * Game.CellSize))
-			{
-				var rawSpeed = .2f * Util.GetEffectiveSpeed(self, UnitMovementType.Fly);
-				self.CenterLocation += (rawSpeed / dist.Length) * dist;
-				self.Location = ((1 / 24f) * self.CenterLocation).ToInt2();
-			}
+			var rawSpeed = .2f * Util.GetEffectiveSpeed(self, UnitMovementType.Fly);
+
+			if (!float2.WithinEpsilon(float2.Zero, dist, range * Game.CellSize))
+				self.CenterLocation += (rawSpeed / dist.Length) * dist;
+
+			var otherHelis = self.World.FindUnitsInCircle(self.CenterLocation, AvoidDist)
+				.Where(a => a.traits.Contains<Helicopter>());
+
+			var f = otherHelis
+				.Select(h => GetRepulseForce(self, h))
+				.Aggregate(float2.Zero, (a, b) => a + b);
+
+			self.CenterLocation += rawSpeed * f;
+
+			self.Location = ((1 / 24f) * self.CenterLocation).ToInt2();
 
-			/* todo: maintain seperation wrt other helis */
 			return this;
 		}
 
+		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) { target = null; NextActivity = null; }
 	}
 }