Added LineImpactProjectile.

OpenRA.Game/WPos.cs

@@ -40,6 +40,20 @@ namespace OpenRA
 		/// </summary>
 		public static WPos Lerp(WPos a, WPos b, int mul, int div) { return a + (b - a) * mul / div; }
 
+		/// <summary>
+		/// Returns the linear interpolation between points 'a' and 'b'
+		/// </summary>
+		public static WPos Lerp(WPos a, WPos b, long mul, long div)
+		{
+			// The intermediate variables may need more precision than
+			// an int can provide, so we can't use WPos.
+			var x = (int)(a.X + (b.X - a.X) * mul / div);
+			var y = (int)(a.Y + (b.Y - a.Y) * mul / div);
+			var z = (int)(a.Z + (b.Z - a.Z) * mul / div);
+
+			return new WPos(x, y, z);
+		}
+
 		public static WPos LerpQuadratic(WPos a, WPos b, WAngle pitch, int mul, int div)
 		{
 			// Start with a linear lerp between the points

OpenRA.Mods.Common/Effects/AreaBeam.cs

@@ -0,0 +1,217 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2015 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation. For more information,
+ * see COPYING.
+ */
+#endregion
+
+using System;
+using System.Collections.Generic;
+using System.Drawing;
+using System.Linq;
+using OpenRA.Effects;
+using OpenRA.GameRules;
+using OpenRA.Graphics;
+using OpenRA.Mods.Common.Graphics;
+using OpenRA.Mods.Common.Traits;
+using OpenRA.Traits;
+
+namespace OpenRA.Mods.Common.Effects
+{
+	public class AreaBeamInfo : IProjectileInfo
+	{
+		[Desc("Projectile speed in WDist / tick, two values indicate a randomly picked velocity per beam.")]
+		public readonly WDist[] Speed = { new WDist(128) };
+
+		[Desc("The maximum duration (in ticks) of each beam burst.")]
+		public readonly int Duration = 10;
+
+		[Desc("The number of ticks between the beam causing warhead impacts in its area of effect.")]
+		public readonly int DamageInterval = 3;
+
+		[Desc("The width of the beam.")]
+		public readonly WDist Width = new WDist(512);
+
+		[Desc("How far beyond the target the projectile keeps on travelling.")]
+		public readonly WDist BeyondTargetRange = new WDist(0);
+
+		[Desc("Damage modifier applied at each range step.")]
+		public readonly int[] Falloff = { 100, 100 };
+
+		[Desc("Ranges at which each Falloff step is defined.")]
+		public readonly WDist[] Range = { WDist.Zero, new WDist(int.MaxValue) };
+
+		[Desc("Maximum offset at the maximum range.")]
+		public readonly WDist Inaccuracy = WDist.Zero;
+
+		[Desc("Can this projectile be blocked when hitting actors with an IBlocksProjectiles trait.")]
+		public readonly bool Blockable = false;
+
+		[Desc("Extra search radius beyond beam width. Required to ensure affecting actors with large health radius.")]
+		public readonly WDist TargetExtraSearchRadius = new WDist(2048);
+
+		[Desc("Should the beam be visuall rendered? False = Beam is invisible.")]
+		public readonly bool RenderBeam = true;
+
+		[Desc("Color of the beam.")]
+		public readonly Color Color = Color.Red;
+
+		[Desc("Beam color is the player's color.")]
+		public readonly bool UsePlayerColor = false;
+
+		public IEffect Create(ProjectileArgs args)
+		{
+			var c = UsePlayerColor ? args.SourceActor.Owner.Color.RGB : Color;
+			return new AreaBeam(this, args, c);
+		}
+	}
+
+	public class AreaBeam : IEffect, ISync
+	{
+		readonly AreaBeamInfo info;
+		readonly ProjectileArgs args;
+		readonly AttackBase actorAttackBase;
+		readonly Color color;
+		readonly WDist speed;
+
+		[Sync] WPos headPos;
+		[Sync] WPos tailPos;
+		[Sync] WPos target;
+		int length;
+		int towardsTargetFacing;
+		int headTicks;
+		int tailTicks;
+		bool isHeadTravelling = true;
+		bool isTailTravelling;
+
+		bool IsBeamComplete { get { return !isHeadTravelling && headTicks >= length &&
+			!isTailTravelling && tailTicks >= length; } }
+
+		public AreaBeam(AreaBeamInfo info, ProjectileArgs args, Color color)
+		{
+			this.info = info;
+			this.args = args;
+			this.color = color;
+			actorAttackBase = args.SourceActor.Trait<AttackBase>();
+
+			var world = args.SourceActor.World;
+			if (info.Speed.Length > 1)
+				speed = new WDist(world.SharedRandom.Next(info.Speed[0].Length, info.Speed[1].Length));
+			else
+				speed = info.Speed[0];
+
+			// Both the head and tail start at the source actor, but initially only the head is travelling.
+			headPos = args.Source;
+			tailPos = headPos;
+
+			target = args.PassiveTarget;
+			if (info.Inaccuracy.Length > 0)
+			{
+				var inaccuracy = OpenRA.Traits.Util.ApplyPercentageModifiers(info.Inaccuracy.Length, args.InaccuracyModifiers);
+				var maxOffset = inaccuracy * (target - headPos).Length / args.Weapon.Range.Length;
+				target += WVec.FromPDF(world.SharedRandom, 2) * maxOffset / 1024;
+			}
+
+			towardsTargetFacing = OpenRA.Traits.Util.GetFacing(target - headPos, 0);
+
+			// Update the target position with the range we shoot beyond the target by
+			// I.e. we can deliberately overshoot, so aim for that position
+			var dir = new WVec(0, -1024, 0).Rotate(WRot.FromFacing(towardsTargetFacing));
+			target += dir * info.BeyondTargetRange.Length / 1024;
+
+			length = Math.Max((target - headPos).Length / speed.Length, 1);
+		}
+
+		public void Tick(World world)
+		{
+			if (++headTicks >= length)
+			{
+				headPos = target;
+				isHeadTravelling = false;
+			}
+			else if (isHeadTravelling)
+				headPos = WPos.LerpQuadratic(args.Source, target, WAngle.Zero, headTicks, length);
+
+			if (tailTicks <= 0 && args.SourceActor.IsInWorld && !args.SourceActor.IsDead)
+			{
+				args.Source = args.CurrentSource();
+				tailPos = args.Source;
+			}
+
+			// Allow for 1 cell (1024) leniency to avoid edge case stuttering (start firing and immediately stop again).
+			var outOfWeaponRange = args.Weapon.Range.Length + 1024 < (args.PassiveTarget - args.Source).Length;
+
+			// While the head is travelling, the tail must start to follow Duration ticks later.
+			// Alternatively, also stop emitting the beam if source actor dies or is ordered to stop.
+			if ((headTicks >= info.Duration && !isTailTravelling) || args.SourceActor.IsDead ||
+				!actorAttackBase.IsAttacking || outOfWeaponRange)
+				isTailTravelling = true;
+
+			if (isTailTravelling)
+			{
+				if (++tailTicks >= length)
+				{
+					tailPos = target;
+					isTailTravelling = false;
+				}
+				else
+					tailPos = WPos.LerpQuadratic(args.Source, target, WAngle.Zero, tailTicks, length);
+			}
+
+			// Check for blocking actors
+			WPos blockedPos;
+			if (info.Blockable && BlocksProjectiles.AnyBlockingActorsBetween(world, tailPos, headPos,
+				info.Width, info.TargetExtraSearchRadius, out blockedPos))
+			{
+				headPos = blockedPos;
+				target = headPos;
+				length = Math.Min(headTicks, length);
+			}
+
+			// Damage is applied to intersected actors every DamageInterval ticks
+			if (headTicks % info.DamageInterval == 0)
+			{
+				var actors = world.FindActorsOnLine(tailPos, headPos, info.Width, info.TargetExtraSearchRadius);
+				foreach (var a in actors)
+				{
+					var adjustedModifiers = args.DamageModifiers.Append(GetFalloff((args.Source - a.CenterPosition).Length));
+					args.Weapon.Impact(Target.FromActor(a), args.SourceActor, adjustedModifiers);
+				}
+			}
+
+			if (IsBeamComplete)
+				world.AddFrameEndTask(w => w.Remove(this));
+		}
+
+		public IEnumerable<IRenderable> Render(WorldRenderer wr)
+		{
+			if (!IsBeamComplete && info.RenderBeam && !(wr.World.FogObscures(tailPos) && wr.World.FogObscures(headPos)))
+			{
+				float width, y, z;
+				wr.ScreenVectorComponents(new WVec(info.Width, WDist.Zero, WDist.Zero), out width, out y, out z);
+				var beamRender = new BeamRenderable(headPos, 0, tailPos - headPos, width, color);
+				return new[] { (IRenderable)beamRender };
+			}
+
+			return SpriteRenderable.None;
+		}
+
+		int GetFalloff(int distance)
+		{
+			var inner = info.Range[0].Length;
+			for (var i = 1; i < info.Range.Length; i++)
+			{
+				var outer = info.Range[i].Length;
+				if (outer > distance)
+					return int2.Lerp(info.Falloff[i - 1], info.Falloff[i], distance - inner, outer - inner);
+
+				inner = outer;
+			}
+
+			return 0;
+		}
+	}
+}

OpenRA.Mods.Common/OpenRA.Mods.Common.csproj

@@ -157,6 +157,7 @@
     <Compile Include="Effects\FloatingText.cs" />
     <Compile Include="Effects\GravityBomb.cs" />
     <Compile Include="Effects\LaserZap.cs" />
+    <Compile Include="Effects\AreaBeam.cs" />
     <Compile Include="Effects\Missile.cs" />
     <Compile Include="Effects\NukeLaunch.cs" />
     <Compile Include="Effects\PowerdownIndicator.cs" />
@@ -533,6 +534,7 @@
     <Compile Include="UtilityCommands\ExtractLanguageStringsCommand.cs" />
     <Compile Include="UtilityCommands\ExtractLuaDocsCommand.cs" />
     <Compile Include="UtilityCommands\ExtractTraitDocsCommand.cs" />
+    <Compile Include="WorldExtensions.cs" />
     <Compile Include="UtilityCommands\GenerateMinimapCommand.cs" />
     <Compile Include="UtilityCommands\GetMapHashCommand.cs" />
     <Compile Include="UtilityCommands\Glob.cs" />

OpenRA.Mods.Common/WorldExtensions.cs

@@ -0,0 +1,99 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2015 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation. For more information,
+ * see COPYING.
+ */
+#endregion
+
+using System;
+using System.Collections.Generic;
+using OpenRA.Mods.Common.Traits;
+
+namespace OpenRA.Mods.Common
+{
+	public static class WorldExtensions
+	{
+		/// <summary>
+		/// Finds all the actors of which their health radius is intersected by a line (with a definable width) between two points.
+		/// </summary>
+		/// <param name="world">The engine world the line intersection is to be done in.</param>
+		/// <param name="lineStart">The position the line should start at</param>
+		/// <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, WDist targetExtraSearchRadius)
+		{
+			// 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.
+			// For actors without a health radius, we simply check their center point.
+			// The square in which we select all actors must be large enough to encompass the entire line's width.
+			var xDir = Math.Sign(lineEnd.X - lineStart.X);
+			var yDir = Math.Sign(lineEnd.Y - lineStart.Y);
+
+			var dir = new WVec(xDir, yDir, 0);
+			var overselect = dir * (1024 + lineWidth.Length + targetExtraSearchRadius.Length);
+			var finalTarget = lineEnd + overselect;
+			var finalSource = lineStart - overselect;
+
+			var actorsInSquare = world.ActorMap.ActorsInBox(finalTarget, finalSource);
+			var intersectedActors = new List<Actor>();
+
+			foreach (var currActor in actorsInSquare)
+			{
+				var actorWidth = 0;
+				var healthInfo = currActor.Info.TraitInfoOrDefault<HealthInfo>();
+				if (healthInfo != null)
+					actorWidth = healthInfo.Radius.Length;
+
+				var projection = MinimumPointLineProjection(lineStart, lineEnd, currActor.CenterPosition);
+				var distance = (currActor.CenterPosition - projection).HorizontalLength;
+				var maxReach = actorWidth + lineWidth.Length;
+
+				if (distance <= maxReach)
+					intersectedActors.Add(currActor);
+			}
+
+			return intersectedActors;
+		}
+
+		/// <summary>
+		/// Find the point (D) on a line (A-B) that is closest to the target point (C).
+		/// </summary>
+		/// <param name="lineStart">The source point (tail) of the line</param>
+		/// <param name="lineEnd">The target point (head) of the line</param>
+		/// <param name="point">The target point that the minimum distance should be found to</param>
+		/// <returns>The WPos that is the point on the line that is closest to the target point</returns>
+		public static WPos MinimumPointLineProjection(WPos lineStart, WPos lineEnd, WPos point)
+		{
+			var squaredLength = (lineEnd - lineStart).HorizontalLengthSquared;
+
+			// Line has zero length, so just use the lineEnd position as the closest position.
+			if (squaredLength == 0)
+				return lineEnd;
+
+			// Consider the line extending the segment, parameterized as target + t (source - target).
+			// We find projection of point onto the line.
+			// It falls where t = [(point - target) . (source - target)] / |source - target|^2
+			// The normal DotProduct math would be (xDiff + yDiff) / dist, where dist = (target - source).LengthSquared;
+			// But in order to avoid floating points, we do not divide here, but rather work with the large numbers as far as possible.
+			// We then later divide by dist, only AFTER we have multiplied by the dotproduct.
+			var xDiff = ((long)point.X - lineEnd.X) * (lineStart.X - lineEnd.X);
+			var yDiff = ((long)point.Y - lineEnd.Y) * (lineStart.Y - lineEnd.Y);
+			var t = xDiff + yDiff;
+
+			// Beyond the 'target' end of the segment
+			if (t < 0)
+				return lineEnd;
+
+			// Beyond the 'source' end of the segment
+			if (t > squaredLength)
+				return lineStart;
+
+			// Projection falls on the segment
+			return WPos.Lerp(lineEnd, lineStart, t, squaredLength);
+		}
+	}
+}