New Atlas + Texture Pipeline

Core/Game.cs

@@ -34,7 +34,7 @@ public sealed class Game : GameWindow
         GL.Enable(EnableCap.CullFace);
 
         this._shader = new Shader("Assets/shaders/chunk.vert", "Assets/shaders/chunk.frag");
-        this._texture = new Texture("Assets/textures/atlas.png");
+        this._texture = new Texture("Assets/textures/VoxelShadeAtlas.png");
 
         this._world = new World.World(this._registry);
 

VoxelEngine.Tests/BlockRegistryTests.cs

@@ -34,9 +34,9 @@ public class BlockRegistryTests
         var registry = new BlockRegistry();
         IBlock grass = registry.Get(3);
 
-        Assert.Equal(0, grass.GetTextureIndex(BlockFace.Top));
+        Assert.Equal(new TileCoord(0, 1), grass.GetTextureTile(BlockFace.Top));
-        Assert.Equal(1, grass.GetTextureIndex(BlockFace.Bottom));
+        Assert.Equal(new TileCoord(0, 0), grass.GetTextureTile(BlockFace.Bottom));
-        Assert.Equal(3, grass.GetTextureIndex(BlockFace.North));
+        Assert.Equal(new TileCoord(1, 1), grass.GetTextureTile(BlockFace.North));
     }
 
     [Fact]

VoxelEngine.csproj

@@ -10,6 +10,7 @@
 
     <ItemGroup>
         <PackageReference Include="OpenTK" Version="4.9.4" />
+        <PackageReference Include="SimplexNoise" Version="2.0.0" />
         <PackageReference Include="StbImageSharp" Version="2.30.15" />
     </ItemGroup>
 

World/Blocks/AirBlock.cs

@@ -6,5 +6,5 @@ public sealed class AirBlock : IBlock
     public string Name => "Air";
     public bool IsOpaque => false;
     public bool IsSolid => false;
-    public int GetTextureIndex(BlockFace face) => 0;
+    public TileCoord GetTextureTile(BlockFace face) => new(0, 0);
 }

World/Blocks/DirtBlock.cs

@@ -6,5 +6,5 @@ public sealed class DirtBlock : IBlock
     public string Name => "Dirt";
     public bool IsOpaque => true;
     public bool IsSolid => true;
-    public int GetTextureIndex(BlockFace face) => 1;
+    public TileCoord GetTextureTile(BlockFace face) => new(0, 0);
 }

World/Blocks/GrassBlock.cs

@@ -7,10 +7,10 @@ public sealed class GrassBlock : IBlock
     public bool IsOpaque => true;
     public bool IsSolid => true;
 
-    public int GetTextureIndex(BlockFace face) => face switch
+    public TileCoord GetTextureTile(BlockFace face) => face switch
     {
-        BlockFace.Top => 0,    // grass top
+        BlockFace.Top => new(0, 1),    // grass top
-        BlockFace.Bottom => 1, // dirt
+        BlockFace.Bottom => new(0, 0), // dirt
-        _ => 3                 // grass side
+        _ => new(1, 1)                 // grass side
     };
 }

World/Blocks/IBlock.cs

@@ -11,8 +11,8 @@ public interface IBlock
     // Reserved for future collision (not used in the baseline).
     bool IsSolid { get; }
 
-    // Atlas tile index for the given face.
+    // Atlas tile coordinate for the given face.
-    int GetTextureIndex(BlockFace face);
+    TileCoord GetTextureTile(BlockFace face);
 
     // Interaction hooks — capability present now, system built post-baseline.
     void OnInteract() { }

World/Blocks/StoneBlock.cs

@@ -6,5 +6,5 @@ public sealed class StoneBlock : IBlock
     public string Name => "Stone";
     public bool IsOpaque => true;
     public bool IsSolid => true;
-    public int GetTextureIndex(BlockFace face) => 2;
+    public TileCoord GetTextureTile(BlockFace face) => new(1, 0);
 }

World/Chunk/ChunkMesher.cs

@@ -4,7 +4,10 @@ namespace VoxelEngine.World.Chunk;
 
 public sealed class ChunkMesher : IChunkMesher
 {
-    private const int AtlasTiles = 4; // horizontal strip of 4 tiles
+    private const int TileSizePixels = 32;  // each tile is 32x32 pixels
+    private const int AtlasSizePixels = 64; // atlas is 64x64 pixels (2x2 grid)
+
+    private const float TileSize = (float)TileSizePixels / AtlasSizePixels; // normalized tile size
 
     // Per-face geometry: base corner + two in-plane edge vectors (u, v) with
     // cross(u, v) == outward normal, guaranteeing CCW winding from outside.
@@ -69,17 +72,18 @@ public sealed class ChunkMesher : IChunkMesher
                         : (neighborOpaqueOutside?.Invoke(nx, ny, nz) ?? false);
                 if (neighborOpaque) continue;
 
-                ChunkMesher.AddFace(verts, x, y, z, face, block.GetTextureIndex(face.Kind));
+                ChunkMesher.AddFace(verts, x, y, z, face, block.GetTextureTile(face.Kind));
             }
         }
 
         return verts.ToArray();
     }
 
-    private static void AddFace(List<float> verts, int x, int y, int z, Face face, int texIndex)
+    private static void AddFace(List<float> verts, int x, int y, int z, Face face, TileCoord tile)
     {
-        float tileWidth = 1f / ChunkMesher.AtlasTiles;
+        float uBase = tile.X * ChunkMesher.TileSize;
-        float uBase = texIndex * tileWidth;
+        // Image is flipped on load, so offset from the top to keep tile (0,0) = top-left.
+        float vBase = 1f - (tile.Y + 1) * ChunkMesher.TileSize;
 
         foreach (int corner in ChunkMesher.Triangle)
         {
@@ -89,10 +93,11 @@ public sealed class ChunkMesher : IChunkMesher
             float py = y + face.Base.y + face.U.y * cu + face.V.y * cv;
             float pz = z + face.Base.z + face.U.z * cu + face.V.z * cv;
 
-            float u = uBase + cu * tileWidth;
+            float u = uBase + cu * ChunkMesher.TileSize;
+            float v = vBase + cv * ChunkMesher.TileSize;
 
             verts.Add(px); verts.Add(py); verts.Add(pz);
-            verts.Add(u); verts.Add(cv);
+            verts.Add(u); verts.Add(v);
             verts.Add(face.Shade);
         }
     }