homing weapons more or less work now

OpenRa.Game/Combat.cs

@@ -0,0 +1,54 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using OpenRa.Game.GameRules;
+using OpenRa.Game.Effects;
+
+namespace OpenRa.Game
+{
+	static class Combat			/* some utility bits that are shared between various things */
+	{
+		public static void DoImpact(int2 loc, int2 visualLoc,
+			WeaponInfo weapon, ProjectileInfo projectile, WarheadInfo warhead, Actor firedBy)
+		{
+			var targetTile = ((1f / Game.CellSize) * loc.ToFloat2()).ToInt2();
+
+			var isWater = Game.IsWater(targetTile);
+			var hitWater = Game.IsCellBuildable(targetTile, UnitMovementType.Float);
+
+			if (warhead.Explosion != 0)
+				Game.world.AddFrameEndTask(
+					w => w.Add(new Explosion(visualLoc, warhead.Explosion, hitWater)));
+
+			var impactSound = warhead.ImpactSound;
+			if (hitWater && warhead.WaterImpactSound != null)
+				impactSound = warhead.WaterImpactSound;
+			if (impactSound != null) Sound.Play(impactSound + ".aud");
+
+			if (!isWater) Smudge.AddSmudge(targetTile, warhead);
+			if (warhead.Ore) Ore.Destroy(targetTile.X, targetTile.Y);
+
+			var maxSpread = GetMaximumSpread(weapon, warhead);
+			var hitActors = Game.FindUnitsInCircle(loc, maxSpread);
+
+			foreach (var victim in hitActors)
+				victim.InflictDamage(firedBy, (int)GetDamageToInflict(victim, loc, weapon, warhead));
+		}
+
+		static float GetMaximumSpread(WeaponInfo weapon, WarheadInfo warhead)
+		{
+			return (int)(warhead.Spread * Math.Log(weapon.Damage, 2));
+		}
+
+		static float GetDamageToInflict(Actor target, int2 loc, WeaponInfo weapon, WarheadInfo warhead)
+		{
+			/* todo: some things can't be damaged AT ALL by certain weapons! */
+			var distance = (target.CenterLocation - loc).Length;
+			var rawDamage = weapon.Damage * (float)Math.Exp(-distance / warhead.Spread);
+			var multiplier = warhead.EffectivenessAgainst(target.Info.Armor);
+
+			return rawDamage * multiplier;
+		}
+	}
+}