Add VTOL landing exhaust animation.

OpenRA.Mods.Common/Activities/Air/Land.cs

@@ -226,6 +226,9 @@ namespace OpenRA.Mods.Common.Activities
 				if (aircraft.Info.LandingSounds.Length > 0)
 					Game.Sound.Play(SoundType.World, aircraft.Info.LandingSounds, self.World, aircraft.CenterPosition);
 
+				foreach (var notify in self.TraitsImplementing<INotifyLanding>())
+					notify.Landing(self);
+
 				aircraft.AddInfluence(landingCell);
 				aircraft.EnteringCell(self);
 				landingInitiated = true;

OpenRA.Mods.Common/Activities/Air/TakeOff.cs

@@ -36,6 +36,9 @@ namespace OpenRA.Mods.Common.Activities
 
 			if (aircraft.Info.TakeoffSounds.Length > 0)
 				Game.Sound.Play(SoundType.World, aircraft.Info.TakeoffSounds, self.World, aircraft.CenterPosition);
+
+			foreach (var notify in self.TraitsImplementing<INotifyTakeOff>())
+				notify.TakeOff(self);
 		}
 
 		public override bool Tick(Actor self)

OpenRA.Mods.Common/Traits/Render/WithAircraftLandingEffect.cs

@@ -0,0 +1,82 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2022 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, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System.Collections.Generic;
+using OpenRA.Graphics;
+using OpenRA.Mods.Common.Effects;
+using OpenRA.Traits;
+
+namespace OpenRA.Mods.Common.Traits.Render
+{
+	[Desc("Plays an animation on the ground position when the actor lands.")]
+	public class WithAircraftLandingEffectInfo : ConditionalTraitInfo
+	{
+		[FieldLoader.Require]
+		public readonly string Image = null;
+
+		[SequenceReference(nameof(Image))]
+		public readonly string[] Sequences = { "idle" };
+
+		[PaletteReference]
+		public readonly string Palette = "effect";
+
+		[Desc("Should the sprite effect be visible through fog.")]
+		public readonly bool VisibleThroughFog = false;
+
+		[Desc("Height at which to play the animation when descending.")]
+		public readonly WDist DistanceAboveTerrain = new WDist(756);
+
+		[Desc("Only play on these terrain types.")]
+		public readonly HashSet<string> TerrainTypes = new HashSet<string>();
+
+		public override object Create(ActorInitializer init) { return new WithAircraftLandingEffect(this); }
+	}
+
+	public class WithAircraftLandingEffect : ConditionalTrait<WithAircraftLandingEffectInfo>, INotifyLanding, ITick
+	{
+		bool shouldAddEffect;
+
+		public WithAircraftLandingEffect(WithAircraftLandingEffectInfo info)
+			: base(info) { }
+
+		void AddEffect(Actor self)
+		{
+			var position = self.CenterPosition - new WVec(WDist.Zero, WDist.Zero, self.World.Map.DistanceAboveTerrain(self.CenterPosition));
+			self.World.AddFrameEndTask(w => w.Add(new SpriteEffect(position, self.World, Info.Image,
+				Info.Sequences.Random(Game.CosmeticRandom), Info.Palette, Info.VisibleThroughFog)));
+		}
+
+		bool ShouldAddEffect(Map map, CPos cell)
+		{
+			if (Info.TerrainTypes.Count == 0)
+				return true;
+
+			return map.Contains(cell) && Info.TerrainTypes.Contains(map.GetTerrainInfo(cell).Type);
+		}
+
+		void INotifyLanding.Landing(Actor self)
+		{
+			shouldAddEffect = ShouldAddEffect(self.World.Map, self.Location);
+		}
+
+		void ITick.Tick(Actor self)
+		{
+			if (!shouldAddEffect)
+				return;
+
+			if (self.World.Map.DistanceAboveTerrain(self.CenterPosition) > Info.DistanceAboveTerrain)
+				return;
+
+			AddEffect(self);
+			shouldAddEffect = false;
+		}
+	}
+}

OpenRA.Mods.Common/TraitsInterfaces.cs

@@ -147,6 +147,11 @@ namespace OpenRA.Mods.Common.Traits
 		void StoppingResupply(Actor self, Actor host);
 	}
 
+	[RequireExplicitImplementation]
+	public interface INotifyTakeOff { void TakeOff(Actor self); }
+	[RequireExplicitImplementation]
+	public interface INotifyLanding { void Landing(Actor self); }
+
 	[RequireExplicitImplementation]
 	public interface INotifyPowerLevelChanged { void PowerLevelChanged(Actor self); }
 	public interface INotifySupportPower { void Charged(Actor self); void Activated(Actor self); }