82 lines
2.7 KiB
C#
82 lines
2.7 KiB
C#
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namespace Theriapolis.Core.World.Generation;
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/// <summary>
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/// Computes 8-connected land-component IDs and sizes via flood fill. Settlement
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/// placement uses this to confine settlements to the main landmass — roads
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/// can't cross ocean, so a settlement on a disconnected island would either be
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/// unreachable or get a sea-crossing straight-line connector stub from
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/// <c>EnsureSettlementConnectivity</c>. 8-connected matches A*'s movement
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/// model so "reachable by road" and "same component" coincide.
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/// </summary>
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internal static class LandmassMap
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{
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private const int W = C.WORLD_WIDTH_TILES;
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private const int H = C.WORLD_HEIGHT_TILES;
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private static readonly (int dx, int dy)[] Neighbors =
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{
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( 0,-1), ( 1,-1), ( 1, 0), ( 1, 1),
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( 0, 1), (-1, 1), (-1, 0), (-1,-1),
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};
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/// <summary>
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/// Returns a pair of arrays: <c>componentId[x,y]</c> gives the 8-connected
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/// land component ID at (x,y), or -1 if (x,y) is ocean; <c>componentSize[id]</c>
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/// gives the tile count of component <paramref name="id"/>.
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/// </summary>
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public static (int[,] componentId, int[] componentSize) Compute(WorldState world)
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{
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var compId = new int[W, H];
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for (int y = 0; y < H; y++)
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for (int x = 0; x < W; x++)
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compId[x, y] = -1;
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var sizes = new List<int>();
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var queue = new Queue<(int x, int y)>();
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for (int y = 0; y < H; y++)
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for (int x = 0; x < W; x++)
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{
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if (compId[x, y] != -1) continue;
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if (world.Tiles[x, y].Biome == BiomeId.Ocean) continue;
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int id = sizes.Count;
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int size = 0;
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compId[x, y] = id;
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queue.Enqueue((x, y));
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while (queue.Count > 0)
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{
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var (cx, cy) = queue.Dequeue();
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size++;
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foreach (var (dx, dy) in Neighbors)
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{
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int nx = cx + dx, ny = cy + dy;
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if ((uint)nx >= W || (uint)ny >= H) continue;
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if (compId[nx, ny] != -1) continue;
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if (world.Tiles[nx, ny].Biome == BiomeId.Ocean) continue;
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compId[nx, ny] = id;
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queue.Enqueue((nx, ny));
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}
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}
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sizes.Add(size);
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}
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return (compId, sizes.ToArray());
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}
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/// <summary>
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/// Returns the component ID of the largest land component, or -1 if the
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/// world has no land.
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/// </summary>
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public static int LargestComponentId(int[] componentSizes)
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{
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int best = -1;
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int bestSize = 0;
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for (int i = 0; i < componentSizes.Length; i++)
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if (componentSizes[i] > bestSize) { bestSize = componentSizes[i]; best = i; }
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return best;
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}
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}
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