Refine map generator spawn placement rules

Spawn generation generally tries to place spawns:

- In spacious areas
- Away from the center (true center or mirror lines)
- Away from a symmetry-projected spawn
- Away from previously placed spawns

This commit introduces the following adjustments:

- The spacing between sequentially placed spawns is relaxed.
- Fix spawn mines contributing too much to the space reservation.
- Factor rotations into anti-center biasing calculation.
- Preserve spacing information in center space fallback decisions.
- Use a linear (instead of binary) falloff for anti-center biasing.
- Enforce that spawns have a minimum buildable area around them.
- Enforce that symmetry-projected spawns have as much separation as
  sequentially placed spawns would.
- Allow spawns on or near roads.

OpenRA.Mods.Common/MapGenerator/Symmetry.cs

@@ -278,26 +278,5 @@ namespace OpenRA.Mods.Common.MapGenerator
 					action(projections, original);
 				}
 		}
-
-		/// <summary>
-		/// Returns true iff xy is within reservationRadius of the center of a given CellLayer. If
-		/// a mirroring is specified, the radius is measured from the mirror line instead of the
-		/// center point.
-		/// </summary>
-		public static bool IsCPosNearCenter<T>(
-			CPos cpos,
-			CellLayer<T> cellLayer,
-			int reservationRadius,
-			Mirror mirror)
-		{
-			CPos[] testPoints;
-			if (mirror == Mirror.None)
-				testPoints = RotateAndMirrorCPos(cpos, cellLayer, 2, Mirror.None);
-			else
-				testPoints = RotateAndMirrorCPos(cpos, cellLayer, 1, mirror);
-
-			var separation = (testPoints[1] - testPoints[0]).LengthSquared;
-			return separation <= reservationRadius * reservationRadius * 4;
-		}
 	}
 }

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

@@ -139,6 +139,8 @@ namespace OpenRA.Mods.Common.Traits
 			[FieldLoader.Require]
 			public readonly int SpawnBuildSize = default;
 			[FieldLoader.Require]
+			public readonly int MinimumSpawnRadius = default;
+			[FieldLoader.Require]
 			public readonly int SpawnResourceSpawns = default;
 			[FieldLoader.Require]
 			public readonly int SpawnReservation = default;
@@ -204,6 +206,8 @@ namespace OpenRA.Mods.Common.Traits
 			[FieldLoader.Ignore]
 			public readonly IReadOnlySet<byte> DominantTerrain;
 			[FieldLoader.Ignore]
+			public readonly IReadOnlySet<byte> ZoneableTerrain;
+			[FieldLoader.Ignore]
 			public readonly IReadOnlySet<string> PartiallyPlayableCategories;
 			[FieldLoader.Ignore]
 			public readonly IReadOnlyList<string> ClearSegmentTypes;
@@ -290,6 +294,7 @@ namespace OpenRA.Mods.Common.Traits
 				PartiallyPlayableTerrain = ParseTerrainIndexes("PartiallyPlayableTerrain");
 				UnplayableTerrain = ParseTerrainIndexes("UnplayableTerrain");
 				DominantTerrain = ParseTerrainIndexes("DominantTerrain");
+				ZoneableTerrain = ParseTerrainIndexes("ZoneableTerrain");
 
 				PartiallyPlayableCategories = my.NodeWithKey("PartiallyPlayableCategories").Value.Value
 					.Split(',', StringSplitOptions.RemoveEmptyEntries)
@@ -394,6 +399,8 @@ namespace OpenRA.Mods.Common.Traits
 					throw new MapGenerationException("SpawnReservation must be >= 1");
 				if (SpawnBuildSize < 1)
 					throw new MapGenerationException("SpawnBuildSize must be >= 1");
+				if (MinimumSpawnRadius < 1)
+					throw new MapGenerationException("MinimumSpawnRadius must be >= 1");
 				if (SpawnResourceSpawns < 0)
 					throw new MapGenerationException("SpawnResourceSpawns must be >= 0");
 				if (ResourceSpawnReservation < 1)
@@ -1167,18 +1174,23 @@ namespace OpenRA.Mods.Common.Traits
 					(projections, cpos) =>
 						projectionSpacing[cpos] = Symmetry.ProjectionProximity(projections) / 2);
 
-				var spawnReservationRadius = minSpan * param.CentralSpawnReservationFraction / FractionMax;
-				var spawnReservation = new CellLayer<bool>(map);
+				// Spawn bias tries to move spawns away from the map center and their symmetry
+				// projections.
+				var spawnBiasRadius = Math.Max(1, minSpan * param.CentralSpawnReservationFraction / FractionMax);
+				var spawnBias = new CellLayer<int>(map);
+				spawnBias.Clear(spawnBiasRadius);
+				CellLayerUtils.OverCircle(
+					cellLayer: spawnBias,
+					wCenter: wMapCenter,
+					wRadius: 1024 * spawnBiasRadius,
+					outside: false,
+					action: (mpos, _, _, wrSq) => spawnBias[mpos] = (int)Exts.ISqrt(wrSq) / 1024);
 				foreach (var mpos in map.AllCells.MapCoords)
-					spawnReservation[mpos] = Symmetry.IsCPosNearCenter(
-						mpos.ToCPos(gridType),
-						spawnReservation,
-						spawnReservationRadius,
-						param.Mirror);
+					spawnBias[mpos] = Math.Min(spawnBias[mpos], projectionSpacing[mpos]);
 
 				var zoneable = new CellLayer<bool>(map);
 				foreach (var mpos in map.AllCells.MapCoords)
-					zoneable[mpos] = playableArea[mpos] && param.ClearTerrain.Contains(tileset.GetTerrainIndex(map.Tiles[mpos]));
+					zoneable[mpos] = playableArea[mpos] && param.ZoneableTerrain.Contains(tileset.GetTerrainIndex(map.Tiles[mpos]));
 
 				foreach (var actorPlan in actorPlans)
 					foreach (var cpos in actorPlan.Footprint().Keys)
@@ -1198,7 +1210,7 @@ namespace OpenRA.Mods.Common.Traits
 					zoneable = newZoneable;
 				}
 
-				if (param.Rotations > 1 || param.Mirror != 0)
+				if (param.Rotations > 1 || param.Mirror != Symmetry.Mirror.None)
 				{
 					// Reserve the center of the map - otherwise it will mess with rotations
 					CellLayerUtils.OverCircle(
@@ -1221,14 +1233,15 @@ namespace OpenRA.Mods.Common.Traits
 					var spawnPreference = new CellLayer<int>(map);
 					CellLayerUtils.ChebyshevRoom(spawnPreference, zoneable, false);
 					foreach (var mpos in map.AllCells.MapCoords)
-					{
-						var preference = Math.Min(spawnPreference[mpos], projectionSpacing[mpos]);
-						if (spawnReservation[mpos] && preference > 1)
-							preference = 1;
-						else if (preference > param.SpawnRegionSize)
-							preference = param.SpawnRegionSize;
-						spawnPreference[mpos] = preference;
-					}
+						if (spawnPreference[mpos] >= param.MinimumSpawnRadius &&
+							projectionSpacing[mpos] * 2 >= param.SpawnReservation + param.MinimumSpawnRadius)
+						{
+							spawnPreference[mpos] = spawnBias[mpos] * Math.Min(param.SpawnRegionSize, spawnPreference[mpos]);
+						}
+						else
+						{
+							spawnPreference[mpos] = 0;
+						}
 
 					var (chosenMPos, chosenValue) = CellLayerUtils.FindRandomBest(
 						spawnPreference,
@@ -1238,7 +1251,6 @@ namespace OpenRA.Mods.Common.Traits
 					if (chosenValue < 1)
 						throw new MapGenerationException("Not enough room for player spawns");
 
-					var room = chosenValue - 1;
 					var spawn = new ActorPlan(map, "mpspawn")
 					{
 						Location = chosenMPos.ToCPos(gridType),
@@ -1299,7 +1311,7 @@ namespace OpenRA.Mods.Common.Traits
 						CellLayerUtils.OverCircle(
 							cellLayer: zoneable,
 							wCenter: projectedResourceSpawn.WPosLocation,
-							wRadius: param.SpawnReservation * 1024,
+							wRadius: param.ResourceSpawnReservation * 1024,
 							outside: false,
 							action: (mpos, _, _, _) => zoneable[mpos] = false);
 				}

mods/cnc/rules/map-generators.yaml

@@ -34,8 +34,9 @@
 						ResourceSpawnReservation: 8
 						SpawnRegionSize: 12
 						SpawnBuildSize: 8
+						MinimumSpawnRadius: 5
 						SpawnResourceSpawns: 3
-						SpawnReservation: 20
+						SpawnReservation: 16
 						SpawnResourceBias: 1050
 						ResourcesPerPlayer: 50000
 						OreUniformity: 500
@@ -56,6 +57,7 @@
 						PartiallyPlayableTerrain: River,Tree,Water
 						UnplayableTerrain: Rock
 						DominantTerrain: River,Rock,Tree,Water
+						ZoneableTerrain: Clear,Road
 						PartiallyPlayableCategories: Beach,Road
 						ClearSegmentTypes: Clear
 						BeachSegmentTypes: Beach

mods/ra/rules/map-generators.yaml

@@ -34,8 +34,9 @@
 						ResourceSpawnReservation: 8
 						SpawnRegionSize: 12
 						SpawnBuildSize: 8
+						MinimumSpawnRadius: 5
 						SpawnResourceSpawns: 3
-						SpawnReservation: 20
+						SpawnReservation: 16
 						SpawnResourceBias: 1150
 						ResourcesPerPlayer: 50000
 						OreUniformity: 250
@@ -55,6 +56,7 @@
 						PartiallyPlayableTerrain: Tree
 						UnplayableTerrain: River,Rock
 						DominantTerrain: River,Rock,Tree,Water
+						ZoneableTerrain: Clear,Road
 						PartiallyPlayableCategories: Beach,Road
 						ClearSegmentTypes: Clear
 						BeachSegmentTypes: Beach
@@ -159,6 +161,7 @@
 					Settings:
 						Water: 800
 						Forests: 0
+						MinimumSpawnRadius: 4
 				Choice@LargeIslands:
 					Label: label-ra-map-generator-choice-terrain-type-large-islands
 					Settings:
@@ -181,6 +184,7 @@
 						TerrainFeatureSize: 5120
 						Forests: 0
 						SpawnBuildSize: 6
+						MinimumSpawnRadius: 4
 			Option@Rotations:
 				Label: label-ra-map-generator-option-rotations
 				SimpleChoice: Rotations