fix local offset -> screen space transform to work as advertised

OpenRA.Mods.RA/AttackBase.cs

@@ -195,12 +195,6 @@ namespace OpenRA.Mods.RA
 			if (!w.IsValidAgainst(target)) return false;
 
 			var barrel = w.Barrels[w.Burst % w.Barrels.Length];
-		
-			var fireOffset = new[] { 
-				w.Turret.UnitSpacePosition.X + barrel.Position.X,
-				w.Turret.UnitSpacePosition.Y + barrel.Position.Y,
-				w.Turret.ScreenSpacePosition.X,
-				w.Turret.ScreenSpacePosition.Y };		// todo: retardage.
 
 			var destUnit = target.IsActor ? target.Actor.traits.GetOrDefault<Unit>() : null;
 
@@ -211,7 +205,9 @@ namespace OpenRA.Mods.RA
 				firedBy = self,
 				target = this.target,
 
-				src = self.CenterLocation.ToInt2() + Combat.GetTurretPosition(self, unit, new Turret(fireOffset)).ToInt2(),
+				src = (self.CenterLocation
+					+ Combat.GetTurretPosition(self, unit, w.Turret)
+					+ Combat.GetBarrelPosition(self, unit, w.Turret, barrel)).ToInt2(),
 				srcAltitude = unit != null ? unit.Altitude : 0,
 				dest = target.CenterLocation.ToInt2(),
 				destAltitude = destUnit != null ? destUnit.Altitude : 0,

OpenRA.Mods.RA/Combat.cs

@@ -199,8 +199,22 @@ namespace OpenRA.Mods.RA
 			var bodyFacing = unit.Facing;
 			var quantizedFacing = Util.QuantizeFacing(bodyFacing, numDirs) * (256 / numDirs);
 
-			return (Util.RotateVectorByFacing(turret.UnitSpacePosition, quantizedFacing, .7f) + GetRecoil(self, turret.Recoil))
+			return (Util.RotateVectorByFacing(turret.UnitSpacePosition, quantizedFacing, .7f) 
+				+ GetRecoil(self, turret.Recoil))
 				+ turret.ScreenSpacePosition;
 		}
+
+		// gets the screen-space position of a barrel.
+		public static float2 GetBarrelPosition(Actor self, Unit unit, Turret turret, Barrel barrel)
+		{
+			var turreted = self.traits.GetOrDefault<Turreted>();
+			
+			if (turreted == null && unit == null)
+				return float2.Zero;
+
+			var turretFacing = turreted != null  ? turreted.turretFacing : unit.Facing;
+
+			return Util.RotateVectorByFacing(barrel.Position, turretFacing, .7f);
+		}
 	}
 }