perf:greedy meshing (#23)

* feat(gameplay): implement greedy meshing for chunk generation

Replace the per-face vertex generation with a greedy meshing algorithm that merges adjacent faces of the same block type into larger quads. Introduce `FaceKey` struct and helper functions (`axis_dir_to_face`, `get_block_safe`, `is_face_culled`, `choose_buf`) to support the new algorithm. Comment out the old `gen_vertices` implementation.

In texture management, rename `m_pbr_texture_array` to `m_normal_texture_array` to reflect its actual usage, and set texture wrap mode to `GL_REPEAT` for both the block and normal texture arrays.

* fix(primitive_data): correct back face texture coordinates and tangents

* fix(texture-manager): correct texture deletion and refactor reload

Make hot_reload private and add public need_reload method. Update UI to call need_reload instead of hot_reload. Fix incorrect use of glDeleteBuffers for normal texture array by using glDeleteTextures.

include/Cubed/gameplay/chunk.hpp

@@ -25,6 +25,18 @@ class Chunk {
 private:
     using OptionalBlockVectorArray =
         std::array<std::optional<std::vector<BlockType>>, 4>;
+
+    struct FaceKey {
+        BlockType block_id = 0;
+        int face = -1; // 0-5, used to index NORMALS/TANGENTS/TEX_COORDS
+
+        bool valid() const { return block_id != 0; }
+        bool operator==(const FaceKey& o) const {
+            return block_id == o.block_id && face == o.face;
+        }
+        bool operator!=(const FaceKey& o) const { return !(*this == o); }
+    };
+
     static constexpr int SIZE_X = CHUNK_SIZE;
     static constexpr int SIZE_Y = WORLD_SIZE_Y;
     static constexpr int SIZE_Z = CHUNK_SIZE;
@@ -66,6 +78,8 @@ private:
     void gen_vertices(const OptionalBlockVectorArray& neighbor_block);
     void gen_cross_plane_vertices(int world_x, int world_y, int world_z,
                                   BlockType id);
+    void emit_quad(int axis, int face_dir, int layer, int i, int j, int w,
+                   int h, int u_axis, int v_axis, FaceKey key);
 
 public:
     Chunk(World& world, ChunkPos chunk_pos, bool temp_chunk = false);

include/Cubed/primitive_data.hpp

@@ -63,12 +63,12 @@ constexpr float TEX_COORDS[6][6][2] = {
      {0.0f, 0.0f},  // top front
      {0.0f, 1.0f}}, // bottom front
     // ===== back (z = -1) =====
-    {{1.0f, 1.0f},  // bottom left
-     {0.0f, 1.0f},  // bottom right
-     {0.0f, 0.0f},  // top right
-     {0.0f, 0.0f},  // top right
-     {1.0f, 0.0f},  // top left
-     {1.0f, 1.0f}}, // bottom left
+    {{0.0f, 1.0f},  // bottom left
+     {0.0f, 0.0f},  // top left
+     {1.0f, 0.0f},  // top right
+     {1.0f, 0.0f},  // top right
+     {1.0f, 1.0f},  // bottom right
+     {0.0f, 1.0f}}, // bottom left
     // ===== left (x = -1) =====
     {{1.0f, 1.0f},  // bottom back
      {0.0f, 1.0f},  // bottom front
@@ -152,12 +152,12 @@ constexpr float TANGENTS[6][6][3] = {
      {0.0f, 0.0f, -1.0f},
      {0.0f, 0.0f, -1.0f}},
     // ===== back (z = -1) =====
-    {{-1.0f, 0.0f, 0.0f},
-     {-1.0f, 0.0f, 0.0f},
-     {-1.0f, 0.0f, 0.0f},
-     {-1.0f, 0.0f, 0.0f},
-     {-1.0f, 0.0f, 0.0f},
-     {-1.0f, 0.0f, 0.0f}},
+    {{1.0f, 0.0f, 0.0f},
+     {1.0f, 0.0f, 0.0f},
+     {1.0f, 0.0f, 0.0f},
+     {1.0f, 0.0f, 0.0f},
+     {1.0f, 0.0f, 0.0f},
+     {1.0f, 0.0f, 0.0f}},
     // ===== left (x = -1) =====
     {{0.0f, 0.0f, 1.0f},
      {0.0f, 0.0f, 1.0f},

include/Cubed/texture_manager.hpp

@@ -12,7 +12,7 @@ private:
     GLuint m_texture_array = 0;
     GLuint m_cross_plane_array = 0;
     GLuint m_ui_array = 0;
-    GLuint m_pbr_texture_array = 0;
+    GLuint m_normal_texture_array = 0;
     GLfloat m_max_aniso = 0.0f;
 
     int m_aniso = 1;
@@ -29,6 +29,7 @@ private:
     void init_block();
     void init_ui();
     void init_block_status();
+    void hot_reload();
 
 public:
     TextureManager();
@@ -43,7 +44,7 @@ public:
     const std::vector<GLuint>& item_textures() const;
     // Must call after MapTable::init_map() and glfwMakeContextCurrent(window);
     void init_texture();
-    void hot_reload();
+
     void need_reload();
     void update();
     int max_aniso() const;