Rewrite TS minimap rendering:

* Rename LeftColor and RightColor to MinColor and MaxColor
  These are mapped from LowRadarColor and HighRadarColor in
  the original inis, and appear to be used to set the bounding
  values for selecting a random colour, NOT for left/right
  pixels (which caused noticeably wrong banding).

* Adjust brightness based on terrain height.
  MinHeightColorBrightness and MaxHeightColorBrightness
  were chosen by trial/error to match the original
  map preview rendering.

OpenRA.Game/Map/Map.cs

@@ -702,6 +702,11 @@ namespace OpenRA
 				var pxStride = 4;
 				var minimapData = new byte[stride * height];
 				Color leftColor, rightColor;
+
+				var useHeightModifiers = tileset.MinHeightColorBrightness != 1.0f || tileset.MaxHeightColorBrightness != 1.0f;
+				var minHeightBrightness = tileset.MinHeightColorBrightness;
+				var maxHeightBrightness = tileset.MaxHeightColorBrightness;
+				var heightModifier = 1f / Grid.MaximumTerrainHeight;
 				for (var y = 0; y < height; y++)
 				{
 					for (var x = 0; x < width; x++)
@@ -716,8 +721,21 @@ namespace OpenRA
 						{
 							// Cell contains terrain
 							var type = tileset.GetTileInfo(Tiles[uv]);
-							leftColor = type != null ? type.LeftColor : Color.Black;
-							rightColor = type != null ? type.RightColor : Color.Black;
+							if (type != null)
+							{
+								if (useHeightModifiers)
+								{
+									var left = Exts.ColorLerp(Game.CosmeticRandom.NextFloat(), type.MinColor, type.MaxColor);
+									var right = Exts.ColorLerp(Game.CosmeticRandom.NextFloat(), type.MinColor, type.MaxColor);
+									var scale = float2.Lerp(minHeightBrightness, maxHeightBrightness, heightModifier * Height[uv]);
+									leftColor = Color.FromArgb((int)(scale * left.R).Clamp(0, 255), (int)(scale * left.G).Clamp(0, 255), (int)(scale * left.B).Clamp(0, 255));
+									rightColor = Color.FromArgb((int)(scale * right.R).Clamp(0, 255), (int)(scale * right.G).Clamp(0, 255), (int)(scale * right.B).Clamp(0, 255));
+								}
+								else
+									leftColor = rightColor = type.MinColor;
+							}
+							else
+								leftColor = rightColor = Color.Black;
 						}
 
 						if (isRectangularIsometric)

OpenRA.Game/Map/TileSet.cs

@@ -24,9 +24,8 @@ namespace OpenRA
 		public readonly byte TerrainType = byte.MaxValue;
 		public readonly byte Height;
 		public readonly byte RampType;
-		public readonly Color LeftColor;
-		public readonly Color RightColor;
-
+		public readonly Color MinColor;
+		public readonly Color MaxColor;
 		public readonly float ZOffset = 0.0f;
 		public readonly float ZRamp = 1.0f;
 	}
@@ -106,11 +105,11 @@ namespace OpenRA
 
 			// Fall back to the terrain-type color if necessary
 			var overrideColor = tileSet.TerrainInfo[tile.TerrainType].Color;
-			if (tile.LeftColor == default(Color))
-				tile.GetType().GetField("LeftColor").SetValue(tile, overrideColor);
+			if (tile.MinColor == default(Color))
+				tile.GetType().GetField("MinColor").SetValue(tile, overrideColor);
 
-			if (tile.RightColor == default(Color))
-				tile.GetType().GetField("RightColor").SetValue(tile, overrideColor);
+			if (tile.MaxColor == default(Color))
+				tile.GetType().GetField("MaxColor").SetValue(tile, overrideColor);
 
 			return tile;
 		}
@@ -139,6 +138,8 @@ namespace OpenRA
 		public readonly string[] EditorTemplateOrder;
 		public readonly bool IgnoreTileSpriteOffsets;
 		public readonly bool EnableDepth = false;
+		public readonly float MinHeightColorBrightness = 1.0f;
+		public readonly float MaxHeightColorBrightness = 1.0f;
 
 		[FieldLoader.Ignore]
 		public readonly IReadOnlyDictionary<ushort, TerrainTemplateInfo> Templates;

OpenRA.Mods.Cnc/UtilityCommands/LegacyTilesetImporter.cs

@@ -143,8 +143,8 @@ namespace OpenRA.Mods.Cnc.UtilityCommands
 								if (rampType != 0)
 									data.AppendLine("\t\t\t\tRampType: {0}".F(rampType));
 
-								data.AppendLine("\t\t\t\tLeftColor: {0:X2}{1:X2}{2:X2}".F(s.ReadUInt8(), s.ReadUInt8(), s.ReadUInt8()));
-								data.AppendLine("\t\t\t\tRightColor: {0:X2}{1:X2}{2:X2}".F(s.ReadUInt8(), s.ReadUInt8(), s.ReadUInt8()));
+								data.AppendLine("\t\t\t\tMinColor: {0:X2}{1:X2}{2:X2}".F(s.ReadUInt8(), s.ReadUInt8(), s.ReadUInt8()));
+								data.AppendLine("\t\t\t\tMaxColor: {0:X2}{1:X2}{2:X2}".F(s.ReadUInt8(), s.ReadUInt8(), s.ReadUInt8()));
 								data.AppendLine("\t\t\t\tZOffset: {0}".F(-tileSize.Height / 2.0f));
 								data.AppendLine("\t\t\t\tZRamp: 0");
 							}

OpenRA.Mods.Common/Traits/Player/PlayerRadarTerrain.cs

@@ -91,17 +91,31 @@ namespace OpenRA.Mods.Common.Traits
 		public static Pair<int, int> GetColor(Map map, MPos uv)
 		{
 			var custom = map.CustomTerrain[uv];
-			int leftColor, rightColor;
+			Color leftColor, rightColor;
 			if (custom == byte.MaxValue)
 			{
-				var type = map.Rules.TileSet.GetTileInfo(map.Tiles[uv]);
-				leftColor = type != null ? type.LeftColor.ToArgb() : Color.Black.ToArgb();
-				rightColor = type != null ? type.RightColor.ToArgb() : Color.Black.ToArgb();
+				var tileset = map.Rules.TileSet;
+				var type = tileset.GetTileInfo(map.Tiles[uv]);
+				if (type != null)
+				{
+					if (tileset.MinHeightColorBrightness != 1.0f || tileset.MaxHeightColorBrightness != 1.0f)
+					{
+						var left = Exts.ColorLerp(Game.CosmeticRandom.NextFloat(), type.MinColor, type.MaxColor);
+						var right = Exts.ColorLerp(Game.CosmeticRandom.NextFloat(), type.MinColor, type.MaxColor);
+						var scale = float2.Lerp(tileset.MinHeightColorBrightness, tileset.MaxHeightColorBrightness, map.Height[uv] * 1f / map.Grid.MaximumTerrainHeight);
+						leftColor = Color.FromArgb((int)(scale * left.R).Clamp(0, 255), (int)(scale * left.G).Clamp(0, 255), (int)(scale * left.B).Clamp(0, 255));
+						rightColor = Color.FromArgb((int)(scale * right.R).Clamp(0, 255), (int)(scale * right.G).Clamp(0, 255), (int)(scale * right.B).Clamp(0, 255));
 					}
 					else
-				leftColor = rightColor = map.Rules.TileSet[custom].Color.ToArgb();
+						leftColor = rightColor = type.MinColor;
+				}
+				else
+					leftColor = rightColor = Color.Black;
+			}
+			else
+				leftColor = rightColor = map.Rules.TileSet[custom].Color;
 
-			return Pair.New(leftColor, rightColor);
+			return Pair.New(leftColor.ToArgb(), rightColor.ToArgb());
 		}
 	}
 }

OpenRA.Mods.Common/UpdateRules/Rules/20200503/UpdateTilesetColors.cs

@@ -0,0 +1,50 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2020 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;
+using System.Collections.Generic;
+
+namespace OpenRA.Mods.Common.UpdateRules.Rules
+{
+	class UpdateTilesetColors : UpdateRule
+	{
+		public override string Name { get { return "Rename Tileset LeftColor and RightColor"; } }
+		public override string Description
+		{
+			get
+			{
+				return "The LeftColor and RightColor keys in tilesets have been renamed to MinColor and MaxColor to reflect their proper usage.";
+			}
+		}
+
+		public override IEnumerable<string> UpdateTilesetNode(ModData modData, MiniYamlNode tilesetNode)
+		{
+			if (tilesetNode.Key == "Templates")
+			{
+				foreach (var templateNode in tilesetNode.Value.Nodes)
+				{
+					foreach (var tilesNode in templateNode.ChildrenMatching("Tiles"))
+					{
+						foreach (var node in tilesNode.Value.Nodes)
+						{
+							foreach (var leftNode in node.ChildrenMatching("LeftColor"))
+								leftNode.RenameKey("MinColor");
+							foreach (var leftNode in node.ChildrenMatching("RightColor"))
+								leftNode.RenameKey("MaxColor");
+						}
+					}
+				}
+			}
+
+			yield break;
+		}
+	}
+}

OpenRA.Mods.Common/UpdateRules/UpdatePath.cs

@@ -65,6 +65,7 @@ namespace OpenRA.Mods.Common.UpdateRules
 				new SpawnActorPowerDefaultEffect(),
 				new RemoveConditionManager(),
 				new ConvertSupportPowerRangesToFootprint(),
+				new UpdateTilesetColors(),
 			})
 		};