Fix weather particle physics.

The trait documentation specified that the speed
and offset values are px/tick, but they have actually
always been treated as px/render.

Fix the update logic and rescale the map definitions
to account for the fixed behaviour.

OpenRA.Mods.Common/Traits/World/WeatherOverlay.cs

@@ -27,10 +27,10 @@ namespace OpenRA.Mods.Common.Traits
 		public readonly bool ChangingWindLevel = true;
 
 		[Desc("The levels of wind intensity (particles x-axis movement in px/tick).")]
-		public readonly int[] WindLevels = { -5, -3, -2, 0, 2, 3, 5 };
+		public readonly int[] WindLevels = { -12, -7, -5, 0, 5, 7, 12 };
 
 		[Desc("Works only if ChangingWindLevel is enabled. Min. and max. ticks needed to change the WindLevel.")]
-		public readonly int[] WindTick = { 150, 750 };
+		public readonly int[] WindTick = { 150, 550 };
 
 		[Desc("Hard or soft fading between the WindLevels.")]
 		public readonly bool InstantWindChanges = false;
@@ -45,13 +45,13 @@ namespace OpenRA.Mods.Common.Traits
 		public readonly int[] ScatterDirection = { -1, 1 };
 
 		[Desc("Min. and max. speed at which particles fall in px/tick.")]
-		public readonly float[] Gravity = { 1.00f, 2.00f };
+		public readonly float[] Gravity = { 2.5f, 5f };
 
 		[Desc("The current offset value for the swing movement. SwingOffset min. and max. value in px/tick.")]
-		public readonly float[] SwingOffset = { 1.0f, 1.5f };
+		public readonly float[] SwingOffset = { 2.5f, 3.5f };
 
 		[Desc("The value that particles swing to the side each update. SwingSpeed min. and max. value in px/tick.")]
-		public readonly float[] SwingSpeed = { 0.001f, 0.025f };
+		public readonly float[] SwingSpeed = { 0.0025f, 0.06f };
 
 		[Desc("The value range that can be swung to the left or right. SwingAmplitude min. and max. value in px/tick.")]
 		public readonly float[] SwingAmplitude = { 1.0f, 1.5f };
@@ -140,6 +140,7 @@ namespace OpenRA.Mods.Common.Traits
 		long windUpdateCountdown;
 		Particle[] particles;
 		Size viewportSize;
+		long lastRender;
 
 		public WeatherOverlay(World world, WeatherOverlayInfo info)
 		{
@@ -197,6 +198,12 @@ namespace OpenRA.Mods.Common.Traits
 			var viewport = new Rectangle(center - new int2(viewportSize) / 2, viewportSize);
 			var wcr = Game.Renderer.WorldRgbaColorRenderer;
 
+			// SwingSpeed is defined in px/tick so we must account for the fraction of a tick that elapsed since the last render.
+			// The scale is capped at 1 tick to avoid unexpected behaviour at game start, if RunTime overflows, or if the game stalls.
+			var runtime = Game.RunTime;
+			var tickFraction = Math.Min((runtime - lastRender) * 1f / world.Timestep, 1);
+			lastRender = runtime;
+
 			for (var i = 0; i < particles.Length; i++)
 			{
 				// Simulate wind and gravity effects on the particle
@@ -208,7 +215,7 @@ namespace OpenRA.Mods.Common.Traits
 						swingDirection *= -1;
 
 					var swingOffset = p.SwingOffset + p.SwingDirection * p.SwingSpeed;
-					var pos = p.Pos + new float2(p.DirectionScatterX + p.SwingOffset + windStrength, p.Gravity);
+					var pos = p.Pos + tickFraction * new float2(p.DirectionScatterX + p.SwingOffset + windStrength, p.Gravity);
 					particles[i] = p = new Particle(p, pos, swingDirection, swingOffset);
 				}
 

mods/cnc/maps/gdi06/rules.yaml

@@ -6,12 +6,10 @@ World:
 		StartingMusic: rain
 	WeatherOverlay:
 		ChangingWindLevel: true
-		WindLevels: -5, -3, -2, 0, 2, 3, 5
-		WindTick: 150, 550
 		InstantWindChanges: false
 		UseSquares: false
 		ScatterDirection: 0, 0
-		Gravity: 8.00, 12.00
+		Gravity: 15, 25
 		SwingOffset: 0, 0
 		SwingSpeed: 0, 0
 		SwingAmplitude: 0, 0

mods/ra/maps/a-nuclear-winter/rules.yaml

@@ -1,16 +1,10 @@
 World:
 	WeatherOverlay:
 		ChangingWindLevel: true
-		WindLevels: -5, -3, -2, 0, 2, 3, 5, 6
-		WindTick: 150, 550
 		InstantWindChanges: false
 		UseSquares: true
 		ParticleSize: 2, 3
 		ScatterDirection: -1, 1
-		Gravity: 1.00, 2.00
-		SwingOffset: 1.0, 1.5
-		SwingSpeed: 0.001, 0.025
-		SwingAmplitude: 1.0, 1.5
 		ParticleColors: ECECEC, E4E4E4, D0D0D0, BCBCBC
 		LineTailAlphaValue: 0
 	GlobalLightingPaletteEffect:

mods/ra/maps/fort-lonestar/rules.yaml

@@ -10,7 +10,7 @@ World:
 		WindTick: 150, 550
 		UseSquares: false
 		ScatterDirection: 0, 0
-		Gravity: 8.00, 12.00
+		Gravity: 15, 25
 		SwingOffset: 0, 0
 		SwingSpeed: 0, 0
 		SwingAmplitude: 0, 0

mods/ra/maps/shattered-mountain/rules.yaml

@@ -1,17 +1,10 @@
 World:
 	WeatherOverlay:
 		ChangingWindLevel: true
-		WindLevels: -5, -3, -2, 0, 2, 3, 5, 6
-		WindTick: 150, 550
 		InstantWindChanges: false
 		UseSquares: true
 		ParticleSize: 2, 3
 		ParticleDensityFactor: 8
-		ScatterDirection: -1, 1
-		Gravity: 1.00, 2.00
-		SwingOffset: 1.0, 1.5
-		SwingSpeed: 0.001, 0.025
-		SwingAmplitude: 1.0, 1.5
 		ParticleColors: ECECEC, E4E4E4, D0D0D0, BCBCBC
 		LineTailAlphaValue: 0
 	GlobalLightingPaletteEffect:

mods/ra/maps/snow-town/rules.yaml

@@ -1,16 +1,8 @@
 World:
 	WeatherOverlay:
 		ChangingWindLevel: true
-		WindLevels: -5, -3, -2, 0, 2, 3, 5
-		WindTick: 150, 550
 		InstantWindChanges: false
 		UseSquares: true
-		ParticleSize: 1, 3
-		ScatterDirection: -1, 1
-		Gravity: 1.00, 2.00
-		SwingOffset: 1.0, 1.5
-		SwingSpeed: 0.001, 0.025
-		SwingAmplitude: 1.0, 1.5
 		ParticleColors: ECECEC, E4E4E4, D0D0D0, BCBCBC
 		LineTailAlphaValue: 0
 	GlobalLightingPaletteEffect: