Map Generation Fixes and Tweaks (#4069)

* * Renamed Continents to Two Continents
* Created Four Continents map size
It spawns a vertical and a horizontal ocean to split the map in 4 major continents. Works properly on all sizes and with world wrap

* Fixed Pangea extending to boundaries in rectangular maps
* Unified Pangea for rectangular and hexagonal maps

* Fixed Default map type bias on Rectangular maps. Also removed "pangea effect" on Default: land can spawn with the same probability in the whole map.

* New map type: 4 Corners
* Reverted name change Two Continents to Continents
* Renamed Four Continents to Four Corners (to reflect original name in Civ5)
* Added translation strings

* New map type: 4 Corners
* Reverted name change Two Continents to Continents
* Renamed Four Continents to Four Corners (to reflect original name in Civ5)
* Added translation strings

android/assets/jsons/translations/template.properties

@@ -212,6 +212,7 @@ Default =
 Pangaea = 
 Perlin = 
 Continents = 
+Four Corners = 
 Archipelago = 
 Number of City-States = 
 One City Challenge = 

core/src/com/unciv/logic/map/MapParameters.kt

@@ -102,6 +102,7 @@ object MapShape {
 object MapType {
     const val pangaea = "Pangaea"
     const val continents = "Continents"
+    const val fourCorners = "Four Corners"
     const val perlin = "Perlin"
     const val archipelago = "Archipelago"
 

core/src/com/unciv/logic/map/mapgenerator/MapLandmassGenerator.kt

@@ -1,6 +1,5 @@
 package com.unciv.logic.map.mapgenerator
 
-import com.badlogic.gdx.math.Vector2
 import com.unciv.Constants
 import com.unciv.logic.HexMath
 import com.unciv.logic.map.*
@@ -23,6 +22,7 @@ class MapLandmassGenerator(val randomness: MapGenerationRandomness) {
         when (tileMap.mapParameters.type) {
             MapType.pangaea -> createPangea(tileMap)
             MapType.continents -> createTwoContinents(tileMap)
+            MapType.fourCorners -> createFourCorners(tileMap)
             MapType.perlin -> createPerlin(tileMap)
             MapType.archipelago -> createArchipelago(tileMap)
             MapType.default -> generateLandCellularAutomata(tileMap)
@@ -36,12 +36,17 @@ class MapLandmassGenerator(val randomness: MapGenerationRandomness) {
         }
     }
 
-    private fun smooth(tileMap: TileMap, randomness: MapGenerationRandomness) {
+    /**
+     * Smoothen the map by clustering landmass and oceans with probability [threshold].
+     * [TileInfo]s with more than 3 land neighbours are converted to land.
+     * [TileInfo]s with more than 3 water neighbours are converted to water.
+     */
+    private fun smoothen(tileMap: TileMap, threshold: Double = 1.0) {
         for (tileInfo in tileMap.values) {
-            val numberOfLandNeighbors = tileInfo.neighbors.count { it.baseTerrain == Constants.grassland }
-            if (randomness.RNG.nextFloat() < 0.5f)
+            if (randomness.RNG.nextFloat() > threshold)
                 continue
 
+            val numberOfLandNeighbors = tileInfo.neighbors.count { it.baseTerrain == Constants.grassland }
             if (numberOfLandNeighbors > 3)
                 tileInfo.baseTerrain = Constants.grassland
             else if (numberOfLandNeighbors < 3)
@@ -69,7 +74,7 @@ class MapLandmassGenerator(val randomness: MapGenerationRandomness) {
         val elevationSeed = randomness.RNG.nextInt().toDouble()
         for (tile in tileMap.values) {
             var elevation = randomness.getPerlinNoise(tile, elevationSeed)
-            elevation = (elevation + getCircularNoise(tile, tileMap)) / 2.0
+            elevation = (elevation + getEllipticContinent(tile, tileMap)) / 2.0
             spawnLandOrWater(tile, elevation, tileMap.mapParameters.waterThreshold.toDouble())
         }
     }
@@ -83,9 +88,29 @@ class MapLandmassGenerator(val randomness: MapGenerationRandomness) {
         }
     }
 
-    private fun getCircularNoise(tileInfo: TileInfo, tileMap: TileMap): Double {
+    private fun createFourCorners(tileMap: TileMap) {
+        val elevationSeed = randomness.RNG.nextInt().toDouble()
+        for (tile in tileMap.values) {
+            var elevation = randomness.getPerlinNoise(tile, elevationSeed)
+            elevation = (elevation + getFourCornersTransform(tile, tileMap)) / 2.0
+            spawnLandOrWater(tile, elevation, tileMap.mapParameters.waterThreshold.toDouble())
+        }
+    }
+
+    /**
+     * Create an elevation map that favors a central elliptic continent spanning over 85% - 95% of
+     * the map size.
+     */
+    private fun getEllipticContinent(tileInfo: TileInfo, tileMap: TileMap): Double {
         val randomScale = randomness.RNG.nextDouble()
-        val distanceFactor = percentualDistanceToCenter(tileInfo, tileMap)
+        val ratio = 0.85 + 0.1 * randomness.RNG.nextDouble()
+
+        val a = ratio * tileMap.maxLongitude
+        val b = ratio * tileMap.maxLatitude
+        val x = tileInfo.longitude
+        val y = tileInfo.latitude
+
+        val distanceFactor = x * x / (a * a) + y * y / (b * b)
 
         return min(0.3, 1.0 - (5.0 * distanceFactor * distanceFactor + randomScale) / 3.0)
     }
@@ -107,19 +132,35 @@ class MapLandmassGenerator(val randomness: MapGenerationRandomness) {
         return min(0.2, -1.0 + (5.0 * longitudeFactor.pow(0.6f) + randomScale) / 3.0)
     }
 
-    private fun percentualDistanceToCenter(tileInfo: TileInfo, tileMap: TileMap): Double {
-        val mapRadius = tileMap.mapParameters.mapSize.radius
-        if (tileMap.mapParameters.shape == MapShape.hexagonal)
-            return HexMath.getDistance(Vector2.Zero, tileInfo.position).toDouble() / mapRadius
-        else {
-            val size = HexMath.getEquivalentRectangularSize(mapRadius)
-            return HexMath.getDistance(Vector2.Zero, tileInfo.position).toDouble() / HexMath.getDistance(Vector2.Zero, Vector2(size.x / 2, size.y / 2))
-        }
-    }
+    private fun getFourCornersTransform(tileInfo: TileInfo, tileMap: TileMap): Double {
+        // The idea here is to create a water area separating the two four areas.
+        // So what we do it create a line of water in the middle - where longitude is close to 0.
+        val randomScale = randomness.RNG.nextDouble()
+        var longitudeFactor = abs(tileInfo.longitude) / tileMap.maxLongitude
+        var latitudeFactor = abs(tileInfo.latitude) / tileMap.maxLatitude
 
+        // If this is a world wrap, we want it to be separated on both sides -
+        // so we make the actual strip of water thinner, but we put it both in the middle of the map and on the edges of the map
+        if (tileMap.mapParameters.worldWrap) {
+            longitudeFactor = min(
+                longitudeFactor,
+                (tileMap.maxLongitude - abs(tileInfo.longitude)) / tileMap.maxLongitude
+            ) * 1.5f
+            latitudeFactor = min(
+                latitudeFactor,
+                (tileMap.maxLatitude - abs(tileInfo.latitude)) / tileMap.maxLatitude
+            ) * 1.5f
+        }
+        // there's nothing magical about this, it's just what we got from playing around with a lot of different options -
+        //   the numbers can be changed if you find that something else creates better looking continents
+
+        val landFactor = min(longitudeFactor, latitudeFactor)
+
+        return min(0.2, -1.0 + (5.0 * landFactor.pow(0.5f) + randomScale) / 3.0)
+    }
 
     /**
-     * Generates ridged perlin noise. As for parameters see [getPerlinNoise]
+     * Generates ridged perlin noise. As for parameters see [MapGenerationRandomness.getPerlinNoise]
      */
     private fun getRidgedPerlinNoise(tile: TileInfo, seed: Double,
                                      nOctaves: Int = 10,
@@ -132,46 +173,15 @@ class MapLandmassGenerator(val randomness: MapGenerationRandomness) {
 
     // region Cellular automata
     private fun generateLandCellularAutomata(tileMap: TileMap) {
-        val numSmooth = 4
 
-        // init
         for (tile in tileMap.values) {
-            val terrainType = getInitialTerrainCellularAutomata(tile, tileMap.mapParameters)
-            if (terrainType == TerrainType.Land) tile.baseTerrain = Constants.grassland
-            else tile.baseTerrain = Constants.ocean
+            tile.baseTerrain =
+                if (randomness.RNG.nextDouble() < 0.55) Constants.grassland else Constants.ocean
+
             tile.setTransients()
         }
 
-        //smooth
-        val grassland = Constants.grassland
-        val ocean = Constants.ocean
-
-        for (loop in 0..numSmooth) {
-            for (tileInfo in tileMap.values) {
-                val numberOfLandNeighbors = tileInfo.neighbors.count { it.baseTerrain == grassland }
-                if (tileInfo.baseTerrain == grassland) { // land tile
-                    if (numberOfLandNeighbors < 3)
-                        tileInfo.baseTerrain = ocean
-                } else { // water tile
-                    if (numberOfLandNeighbors > 3)
-                        tileInfo.baseTerrain = grassland
+        smoothen(tileMap)
     }
-            }
-        }
-    }
-
-    private fun getInitialTerrainCellularAutomata(tileInfo: TileInfo, mapParameters: MapParameters): TerrainType {
-        val mapRadius = mapParameters.mapSize.radius
-
-        // default
-        if (HexMath.getDistance(Vector2.Zero, tileInfo.position) > 0.9f * mapRadius) {
-            if (randomness.RNG.nextDouble() < 0.1) return TerrainType.Land else return TerrainType.Water
-        }
-        if (HexMath.getDistance(Vector2.Zero, tileInfo.position) > 0.85f * mapRadius) {
-            if (randomness.RNG.nextDouble() < 0.2) return TerrainType.Land else return TerrainType.Water
-        }
-        if (randomness.RNG.nextDouble() < 0.55) return TerrainType.Land else return TerrainType.Water
-    }
-
     // endregion
 }

core/src/com/unciv/ui/newgamescreen/MapParametersTable.kt

@@ -68,6 +68,7 @@ class MapParametersTable(val mapParameters: MapParameters, val isEmptyMapAllowed
             MapType.default,
             MapType.pangaea,
             MapType.continents,
+            MapType.fourCorners,
             MapType.perlin,
             MapType.archipelago,
             if (isEmptyMapAllowed) MapType.empty else null