feat: add Plains/Desert/Mountains/Forest biomes and registry

VoxelEngine.Tests/WorldGen/BiomeTests.cs

@@ -0,0 +1,46 @@
+using VoxelEngine.World.Blocks;
+using VoxelEngine.World.WorldGen;
+using Xunit;
+
+namespace VoxelEngine.Tests.WorldGen;
+
+public class BiomeTests
+{
+    [Fact]
+    public void Desert_TopAndFiller_AreSand()
+    {
+        var blocks = new BlockRegistry();
+        var biomes = new BiomeRegistry(42, blocks);
+        Assert.Equal("Sand", biomes.Desert.Surface.Top.Name);
+        Assert.Equal("Sand", biomes.Desert.Surface.Filler.Name);
+    }
+
+    [Fact]
+    public void Mountains_UseSnowAboveSnowLine_StoneBelow()
+    {
+        var blocks = new BlockRegistry();
+        var biomes = new BiomeRegistry(42, blocks);
+        Assert.Equal("Stone", biomes.Mountains.TopBlock(70).Name);
+        Assert.Equal("Snow Block", biomes.Mountains.TopBlock(120).Name);
+    }
+
+    [Fact]
+    public void Plains_TopBlock_IsGrass_RegardlessOfHeight()
+    {
+        var blocks = new BlockRegistry();
+        var biomes = new BiomeRegistry(42, blocks);
+        Assert.Equal("Grass", biomes.Plains.TopBlock(40).Name);
+        Assert.Equal("Grass", biomes.Plains.TopBlock(120).Name);
+    }
+
+    [Fact]
+    public void SampleHeight_IsDeterministic()
+    {
+        var blocks = new BlockRegistry();
+        var biomes = new BiomeRegistry(42, blocks);
+        var noise = new NoiseSource(42);
+        float h1 = biomes.Mountains.SampleHeight(noise, 100f, 200f);
+        float h2 = biomes.Mountains.SampleHeight(noise, 100f, 200f);
+        Assert.Equal(h1, h2);
+    }
+}

World/WorldGen/BiomeRegistry.cs

@@ -0,0 +1,20 @@
+using VoxelEngine.World.Blocks;
+using VoxelEngine.World.WorldGen.Biomes;
+
+namespace VoxelEngine.World.WorldGen;
+
+public sealed class BiomeRegistry
+{
+    public IBiome Plains { get; }
+    public IBiome Desert { get; }
+    public IBiome Mountains { get; }
+    public IBiome Forest { get; }
+
+    public BiomeRegistry(int seed, BlockRegistry blocks)
+    {
+        this.Plains = new PlainsBiome(seed, blocks);
+        this.Desert = new DesertBiome(seed, blocks);
+        this.Mountains = new MountainsBiome(seed, blocks);
+        this.Forest = new ForestBiome(seed, blocks);
+    }
+}

World/WorldGen/Biomes/DesertBiome.cs

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+using VoxelEngine.World.Blocks;
+
+namespace VoxelEngine.World.WorldGen.Biomes;
+
+public sealed class DesertBiome : IBiome
+{
+    private readonly FastNoiseLite _detail;
+
+    public string Name => "Desert";
+    public SurfacePalette Surface { get; }
+
+    public DesertBiome(int seed, BlockRegistry blocks)
+    {
+        this._detail = new FastNoiseLite(seed + 101);
+        this._detail.SetNoiseType(FastNoiseLite.NoiseType.OpenSimplex2);
+        this._detail.SetFrequency(0.015f);
+        this.Surface = new SurfacePalette(blocks.Sand, blocks.Sand, blocks.Stone);
+    }
+
+    public float SampleHeight(NoiseSource noise, float worldX, float worldZ)
+        => WorldConstants.SeaLevel + 4f * noise.Continent(worldX, worldZ)
+                                   + 1.5f * this._detail.GetNoise(worldX, worldZ);
+
+    public IBlock TopBlock(int worldY) => this.Surface.Top;
+}

World/WorldGen/Biomes/ForestBiome.cs

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+using VoxelEngine.World.Blocks;
+
+namespace VoxelEngine.World.WorldGen.Biomes;
+
+public sealed class ForestBiome : IBiome
+{
+    private readonly FastNoiseLite _detail;
+
+    public string Name => "Forest";
+    public SurfacePalette Surface { get; }
+
+    public ForestBiome(int seed, BlockRegistry blocks)
+    {
+        this._detail = new FastNoiseLite(seed + 103);
+        this._detail.SetNoiseType(FastNoiseLite.NoiseType.OpenSimplex2);
+        this._detail.SetFrequency(0.03f);
+        this.Surface = new SurfacePalette(blocks.Grass, blocks.Dirt, blocks.Stone);
+    }
+
+    public float SampleHeight(NoiseSource noise, float worldX, float worldZ)
+        => WorldConstants.SeaLevel + 6f * noise.Continent(worldX, worldZ)
+                                   + 4f * this._detail.GetNoise(worldX, worldZ);
+
+    public IBlock TopBlock(int worldY) => this.Surface.Top;
+}

World/WorldGen/Biomes/MountainsBiome.cs

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+using VoxelEngine.World.Blocks;
+
+namespace VoxelEngine.World.WorldGen.Biomes;
+
+public sealed class MountainsBiome : IBiome
+{
+    private const int SnowLine = 96;
+    private readonly FastNoiseLite _ridged;
+    private readonly IBlock _stone;
+    private readonly IBlock _snow;
+
+    public string Name => "Mountains";
+    public SurfacePalette Surface { get; }
+
+    public MountainsBiome(int seed, BlockRegistry blocks)
+    {
+        this._ridged = new FastNoiseLite(seed + 102);
+        this._ridged.SetNoiseType(FastNoiseLite.NoiseType.OpenSimplex2);
+        this._ridged.SetFractalType(FastNoiseLite.FractalType.Ridged);
+        this._ridged.SetFractalOctaves(4);
+        this._ridged.SetFrequency(0.01f);
+        this._stone = blocks.Stone;
+        this._snow = blocks.Snow;
+        this.Surface = new SurfacePalette(blocks.Stone, blocks.Stone, blocks.Stone);
+    }
+
+    public float SampleHeight(NoiseSource noise, float worldX, float worldZ)
+        => WorldConstants.SeaLevel + 10f * noise.Continent(worldX, worldZ)
+                                   + 45f * this._ridged.GetNoise(worldX, worldZ);
+
+    public IBlock TopBlock(int worldY) => worldY >= MountainsBiome.SnowLine ? this._snow : this._stone;
+}

World/WorldGen/Biomes/PlainsBiome.cs

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+using VoxelEngine.World.Blocks;
+
+namespace VoxelEngine.World.WorldGen.Biomes;
+
+public sealed class PlainsBiome : IBiome
+{
+    private readonly FastNoiseLite _detail;
+
+    public string Name => "Plains";
+    public SurfacePalette Surface { get; }
+
+    public PlainsBiome(int seed, BlockRegistry blocks)
+    {
+        this._detail = new FastNoiseLite(seed + 100);
+        this._detail.SetNoiseType(FastNoiseLite.NoiseType.OpenSimplex2);
+        this._detail.SetFrequency(0.02f);
+        this.Surface = new SurfacePalette(blocks.Grass, blocks.Dirt, blocks.Stone);
+    }
+
+    public float SampleHeight(NoiseSource noise, float worldX, float worldZ)
+        => WorldConstants.SeaLevel + 6f * noise.Continent(worldX, worldZ)
+                                   + 2f * this._detail.GetNoise(worldX, worldZ);
+
+    public IBlock TopBlock(int worldY) => this.Surface.Top;
+}