refactor: world generation (#17)

* refactor: use TBB for concurrent hash maps and parallelize chunk processing

* fix: tbb link fail

* refactor(chunk): remove biome check for caves in rivers and oceans

* refactor(random): replace std distributions with custom implementations

Avoid overhead and platform-dependent behavior of `<random>` distributions by using direct engine operations and integer arithmetic. This ensures deterministic, cross-platform results and improves performance.

* refactor(generation): use chunk seed for cave and river paths

- Use per-chunk seed instead of global path_id for cave and river generation.
- Remove unused m_sum variables and m_path_id members.
- Clamp river yaw within 10 degrees of initial direction.
- Fix river radius interpolation (use t instead of 1-t).
- Lower sea level from 64 to 63.

include/Cubed/constants.hpp

@@ -6,7 +6,7 @@ namespace Cubed {
 
 constexpr int WORLD_SIZE_Y = 256;
 constexpr int CHUNK_SIZE = 16;
-constexpr int SEA_LEVEL = 64;
+constexpr int SEA_LEVEL = 63;
 
 constexpr int MAX_UI_NUM = 1;
 constexpr int MAX_BLOCK_STATUS = 1;

include/Cubed/gameplay/cave_carver.hpp

@@ -1,10 +1,14 @@
 #pragma once
 #include "Cubed/gameplay/cave_path.hpp"
+
+#include <tbb/concurrent_hash_map.h>
 namespace Cubed {
 class CaveCarver {
+    using CaveHashMap = tbb::concurrent_hash_map<unsigned, CavePath>;
+
 public:
     CaveCarver();
-    std::unordered_map<unsigned, CavePath>& paths();
+    CaveHashMap& paths();
     void init(unsigned world_seed);
     void reload(unsigned world_seed);
     void add_path(const glm::vec3& pos, unsigned chunk_seed);
@@ -15,9 +19,8 @@ public:
     float& cave_probability();
 
 private:
-    std::unordered_map<unsigned, CavePath> m_paths;
+    CaveHashMap m_paths;
     unsigned m_seed = 0;
-    int m_sum = 0;
     Random m_random;
     float m_cave_probability = 0.035f;
 };

include/Cubed/gameplay/cave_path.hpp

@@ -5,12 +5,16 @@
 #include "Cubed/tools/cubed_random.hpp"
 
 #include <glm/glm.hpp>
-#include <unordered_set>
+#include <tbb/concurrent_hash_map.h>
 namespace Cubed {
 
 class CavePath {
+    using ChunkPosSet =
+        tbb::concurrent_hash_map<ChunkPos, bool, ChunkPos::TBBHash>;
+
 public:
-    CavePath(unsigned int world_seed, int path_id, const glm::vec3& start_pos);
+    CavePath(unsigned int chunk_seed, unsigned world_seed,
+             const glm::vec3& start_pos);
     const std::vector<PathPoint>& points() const;
     void clear_chunk(const ChunkPos& pos);
     bool is_finished() const;
@@ -34,7 +38,6 @@ private:
     static inline int m_step_min = 10;
     static inline int m_step_max = 400;
 
-    int m_path_id = 0;
     unsigned int m_seed = 0;
     float m_yaw = 0.0f;
     float m_pitch = 0.0f;
@@ -44,7 +47,7 @@ private:
     Random m_random;
 
     std::vector<PathPoint> m_points;
-    std::unordered_set<ChunkPos, ChunkPos::Hash> m_pending_chunks;
+    ChunkPosSet m_pending_chunks;
     void collect_path_points();
     void precompute_chunk_coverage();
 };

include/Cubed/gameplay/chunk.hpp

@@ -14,6 +14,8 @@ class World;
 // if want to use, do init_chunk(), gen_vertex_data() and
 class Chunk {
 private:
+    using OptionalBlockVectorArray =
+        std::array<std::optional<std::vector<BlockType>>, 4>;
     static constexpr int SIZE_X = CHUNK_SIZE;
     static constexpr int SIZE_Y = WORLD_SIZE_Y;
     static constexpr int SIZE_Z = CHUNK_SIZE;
@@ -46,8 +48,7 @@ private:
     BiomeConditions m_conditions;
 
     void clear_dirty();
-    void gen_vertices(
-        const std::array<const std::vector<BlockType>*, 4>& neighbor_block);
+    void gen_vertices(const OptionalBlockVectorArray& neighbor_block);
     void gen_cross_plane_vertices(int world_x, int world_y, int world_z,
                                   BlockType id);
 
@@ -97,8 +98,7 @@ public:
     //  1 : (-1, 0)
     //  2 : (0, 1)
     //  3 : (0, -1)
-    void gen_vertex_data(
-        const std::array<const std::vector<BlockType>*, 4>& neighbor_block);
+    void gen_vertex_data(const OptionalBlockVectorArray& neighbor_block);
     void upload_to_gpu();
 
     GLuint get_normal_vao() const;

include/Cubed/gameplay/chunk_generator.hpp

@@ -4,6 +4,7 @@
 #include "Cubed/gameplay/biome.hpp"
 #include "Cubed/gameplay/block.hpp"
 #include "Cubed/gameplay/builders/biome_builder.hpp"
+#include "Cubed/gameplay/path_point.hpp"
 #include "Cubed/tools/cubed_random.hpp"
 
 #include <atomic>
@@ -61,6 +62,9 @@ private:
     unsigned m_chunk_seed = 0;
 
     void make_biome_builder();
+    void
+    carve_worm(const std::vector<PathPoint>& points, const ChunkPos& chunk_pos,
+               std::function<void(int /*x*/, int /*y*/, int /*z*/)> on_hit);
 };
 
 } // namespace Cubed

include/Cubed/gameplay/chunk_pos.hpp

@@ -16,7 +16,14 @@ struct ChunkPos {
             return h1 ^ (h2 + 0x9e3779b9 + (h1 << 6) + (h1 >> 2));
         }
     };
-
+    struct TBBHash {
+        std::size_t hash(const ChunkPos& p) const {
+            return ChunkPos::Hash{}(p);
+        }
+        bool equal(const ChunkPos& a, const ChunkPos& b) const {
+            return a == b;
+        }
+    };
     ChunkPos operator+(const ChunkPos& pos) const {
         return ChunkPos{x + pos.x, z + pos.z};
     }

include/Cubed/gameplay/river.path.hpp

@@ -5,13 +5,16 @@
 #include "Cubed/tools/cubed_random.hpp"
 
 #include <glm/glm.hpp>
-#include <unordered_set>
+#include <tbb/concurrent_hash_map.h>
 
 namespace Cubed {
 class RiverPath {
+    using ChunkPosSet =
+        tbb::concurrent_hash_map<ChunkPos, bool, ChunkPos::TBBHash>;
 
 public:
-    RiverPath(unsigned int world_seed, int path_id, const glm::vec3& start_pos);
+    RiverPath(unsigned int chunk_seed, unsigned world_seed,
+              const glm::vec3& start_pos);
     const std::vector<PathPoint>& points() const;
     void clear_chunk(const ChunkPos& pos);
     bool is_finished() const;
@@ -32,12 +35,12 @@ private:
     static inline float m_radius_y_max = 8.0f;
     static inline float m_delta_angle_min = -3.0f;
     static inline float m_delta_angle_max = 3.0f;
-    static inline int m_step_min = 150;
+    static inline int m_step_min = 200;
     static inline int m_step_max = 400;
 
-    int m_path_id = 0;
     unsigned int m_seed = 0;
     float m_yaw = 0.0f;
+    float m_initial_yaw = 0.0f;
     float m_pitch = 0.0f;
     int m_step = 0;
     float m_step_len = 1.0f;
@@ -45,7 +48,7 @@ private:
     Random m_random;
 
     std::vector<PathPoint> m_points;
-    std::unordered_set<ChunkPos, ChunkPos::Hash> m_pending_chunks;
+    ChunkPosSet m_pending_chunks;
     void collect_path_points();
     void precompute_chunk_coverage();
 };

include/Cubed/gameplay/river_worm.hpp

@@ -4,13 +4,15 @@
 #include "Cubed/tools/cubed_random.hpp"
 
 #include <glm/glm.hpp>
-#include <unordered_map>
+#include <tbb/concurrent_hash_map.h>
 namespace Cubed {
 
 class RiverWorm {
+    using RiverHashMap = tbb::concurrent_hash_map<unsigned, RiverPath>;
+
 public:
     RiverWorm();
-    std::unordered_map<unsigned, RiverPath>& paths();
+    RiverHashMap& paths();
     void init(unsigned world_seed);
     void reload(unsigned world_seed);
     void add_path(const glm::vec3& pos, unsigned chunk_seed);
@@ -21,9 +23,8 @@ public:
     float& river_probability();
 
 private:
-    std::unordered_map<unsigned, RiverPath> m_paths;
+    RiverHashMap m_paths;
     unsigned m_seed = 0;
-    int m_sum = 0;
     Random m_random;
     float m_probability = 0.01f;
 };

include/Cubed/gameplay/world.hpp

@@ -31,8 +31,10 @@ class Player;
 class TextureManager;
 class World {
 private:
+    using OptionalBlockVectorArray =
+        std::array<std::optional<std::vector<BlockType>>, 4>;
     using ChunkPtrUpdateList = std::vector<std::pair<ChunkPos, Chunk*>>;
-    using ChunkUpdateList = std::vector<std::pair<ChunkPos, Chunk>>;
+    using ChunkPairVector = std::vector<std::pair<ChunkPos, Chunk>>;
     using ConstChunkMap =
         std::unordered_map<ChunkPos, const Chunk*, ChunkPos::Hash>;
     using ChunkPosSet = std::unordered_set<ChunkPos, ChunkPos::Hash>;
@@ -72,14 +74,14 @@ private:
     void sync_player_pos(glm::vec3& player_pos);
     void
     compute_required_chunks(ChunkPosSet& required_chunks,
-                            ChunkHashMap& temp_neighbor,
+                            ChunkPairVector& temp_neighbor,
                             std::vector<ChunkPos>& need_gen_temp_chunks_pos);
     void sync_and_collect_missing_chunks(std::vector<ChunkPos>&,
                                          const ChunkPosSet&);
     void
     build_neighbor_context_for_new_chunks(ConstChunkMap& new_chunks_neighbor,
                                           ChunkPtrUpdateList& affected_neighbor,
-                                          const ChunkUpdateList& new_chunks);
+                                          const ChunkPairVector& new_chunks);
     void build_neighbor_context_for_affected_neighbors(ChunkPtrUpdateList&,
                                                        ConstChunkMap&);
 

include/Cubed/tools/cubed_hash.hpp

@@ -7,7 +7,17 @@ namespace HASH {
 inline std::size_t str(std::string_view value) {
     return std::hash<std::string_view>{}(value);
 }
-inline uint32_t mix_hash(int32_t a, int32_t b, uint32_t fixed_seed) {
+inline uint32_t combine_32(uint32_t seed, uint32_t v) {
+    seed ^= v + 0x9e3779b9 + (seed << 6) + (seed >> 2);
+    return seed;
+}
+inline uint32_t chunk_seed_hash(int32_t a, int32_t b, uint32_t fixed_seed) {
+    uint32_t seed =
+        combine_32(combine_32(fixed_seed, (uint32_t)a), (uint32_t)b);
+    return seed;
+}
+/*
+inline uint32_t chunk_seed_hash(int32_t a, int32_t b, uint32_t fixed_seed) {
     uint32_t h = fixed_seed;
 
     h ^= (uint32_t)a * 0xcc9e2d51u;
@@ -27,10 +37,8 @@ inline uint32_t mix_hash(int32_t a, int32_t b, uint32_t fixed_seed) {
 
     return h;
 }
-inline uint32_t combine_32(uint32_t seed, uint32_t v) {
-    seed ^= v + 0x9e3779b9 + (seed << 6) + (seed >> 2);
-    return seed;
-}
+    */
+
 } // namespace HASH
 
 } // namespace Cubed