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+# Procedural Generation
+
+## Overview
+
+McRogueFace supports procedural content generation through its Grid and Entity systems. The engine provides the spatial containers and rendering, while Python scripts implement generation algorithms like Binary Space Partitioning, Wave Function Collapse, cellular automata, and noise-based terrain.
+
+**Related Pages:**
+- [[Grid-System]] - Spatial containers for generated content
+- [[Entity-Management]] - Populating grids with entities
+- [[AI-and-Pathfinding]] - Walkability and navigation for generated maps
+
+**Key Files:**
+- `src/scripts/cos_level.py` - BSP dungeon generation
+- `src/scripts/cos_tiles.py` - Wave Function Collapse tile placement
+- `src/UIGrid.cpp` - Grid manipulation API
+
+**Related Issues:**
+- [#123](../../issues/123) - Subgrid system for large worlds
+- [#67](../../issues/67) - Grid stitching for seamless chunks
+- [#55](../../issues/55) - Agent simulation demo
+
+---
+
+## Binary Space Partitioning (BSP)
+
+### Dungeon Layout Generation
+
+BSP recursively divides space to create room layouts:
+
+```python
+import random
+import mcrfpy
+
+class BinaryRoomNode:
+    """Node in BSP tree representing a room"""
+    def __init__(self, x, y, w, h):
+        self.x = x
+        self.y = y
+        self.w = w
+        self.h = h
+        self.left = None
+        self.right = None
+    
+    def split(self, min_size=8):
+        """Split this room into two sub-rooms"""
+        # Choose split direction based on aspect ratio
+        if self.w > self.h:
+            direction = "vertical"
+        elif self.h > self.w:
+            direction = "horizontal"
+        else:
+            direction = random.choice(["vertical", "horizontal"])
+        
+        # Calculate split position (30-70%)
+        split_ratio = random.uniform(0.3, 0.7)
+        
+        if direction == "vertical" and self.w >= min_size * 2:
+            split_x = int(self.w * split_ratio)
+            self.left = BinaryRoomNode(self.x, self.y, split_x, self.h)
+            self.right = BinaryRoomNode(self.x + split_x, self.y, 
+                                         self.w - split_x, self.h)
+            return True
+        elif direction == "horizontal" and self.h >= min_size * 2:
+            split_y = int(self.h * split_ratio)
+            self.left = BinaryRoomNode(self.x, self.y, self.w, split_y)
+            self.right = BinaryRoomNode(self.x, self.y + split_y, 
+                                         self.w, self.h - split_y)
+            return True
+        
+        return False  # Can't split further
+    
+    def get_leaves(self):
+        """Get all leaf rooms (no children)"""
+        if self.left is None and self.right is None:
+            return [self]
+        leaves = []
+        if self.left:
+            leaves.extend(self.left.get_leaves())
+        if self.right:
+            leaves.extend(self.right.get_leaves())
+        return leaves
+
+# Generate dungeon layout
+def generate_bsp_dungeon(grid, num_splits=4):
+    w, h = grid.grid_size
+    root = BinaryRoomNode(0, 0, w, h)
+    
+    # Split recursively
+    nodes = [root]
+    for _ in range(num_splits):
+        new_nodes = []
+        for node in nodes:
+            if node.split():
+                new_nodes.extend([node.left, node.right])
+            else:
+                new_nodes.append(node)
+        nodes = new_nodes
+    
+    # Get leaf rooms
+    rooms = root.get_leaves()
+    
+    # Carve rooms into grid
+    for room in rooms:
+        # Add margin
+        rx = room.x + 2
+        ry = room.y + 2
+        rw = room.w - 4
+        rh = room.h - 4
+        
+        for x in range(rx, rx + rw):
+            for y in range(ry, ry + rh):
+                cell = grid.at((x, y))
+                cell.walkable = True
+                cell.tilesprite = 0  # Floor tile
+                cell.color = (128, 128, 128, 255)
+    
+    return rooms
+```
+
+See `src/scripts/cos_level.py` for the complete implementation used in "Crypt of Sokoban."
+
+### Connecting Rooms
+
+After generating rooms, create corridors:
+
+```python
+def carve_corridor(grid, x1, y1, x2, y2):
+    """L-shaped corridor between two points"""
+    # Horizontal first
+    for x in range(min(x1, x2), max(x1, x2) + 1):
+        cell = grid.at((x, y1))
+        cell.walkable = True
+        cell.tilesprite = 0
+    
+    # Then vertical
+    for y in range(min(y1, y2), max(y1, y2) + 1):
+        cell = grid.at((x2, y))
+        cell.walkable = True
+        cell.tilesprite = 0
+
+def connect_rooms(grid, rooms):
+    """Connect all rooms with corridors"""
+    for i in range(len(rooms) - 1):
+        r1 = rooms[i]
+        r2 = rooms[i + 1]
+        
+        # Room centers
+        x1 = r1.x + r1.w // 2
+        y1 = r1.y + r1.h // 2
+        x2 = r2.x + r2.w // 2
+        y2 = r2.y + r2.h // 2
+        
+        carve_corridor(grid, x1, y1, x2, y2)
+```
+
+---
+
+## Wave Function Collapse (WFC)
+
+### Tile-Based Constraint Solving
+
+WFC generates tilemap patterns that satisfy local constraints:
+
+```python
+class TileRule:
+    """Constraint: which tiles can appear adjacent"""
+    def __init__(self, tile_id, north=None, south=None, east=None, west=None):
+        self.tile_id = tile_id
+        self.neighbors = {
+            "north": north or [],
+            "south": south or [],
+            "east": east or [],
+            "west": west or []
+        }
+    
+    def can_place(self, grid, x, y):
+        """Check if tile can be placed at (x, y)"""
+        # Check each neighbor
+        if y > 0:  # North
+            north_tile = grid.at((x, y - 1)).tilesprite
+            if north_tile not in self.neighbors["north"]:
+                return False
+        
+        if y < grid.grid_size[1] - 1:  # South
+            south_tile = grid.at((x, y + 1)).tilesprite
+            if south_tile not in self.neighbors["south"]:
+                return False
+        
+        # ... check east/west similarly
+        return True
+
+# Define tile rules (example: simple dungeon)
+FLOOR = 0
+WALL = 1
+RULES = [
+    TileRule(FLOOR, north=[FLOOR, WALL], south=[FLOOR, WALL],
+             east=[FLOOR, WALL], west=[FLOOR, WALL]),
+    TileRule(WALL, north=[WALL], south=[WALL], 
+             east=[WALL], west=[WALL])
+]
+
+def wfc_generate(grid):
+    """Generate tiles using Wave Function Collapse"""
+    w, h = grid.grid_size
+    
+    # Track cells with multiple possibilities
+    possibilities = {}
+    for x in range(w):
+        for y in range(h):
+            possibilities[(x, y)] = [0, 1]  # Can be floor or wall
+    
+    # Iteratively collapse
+    while possibilities:
+        # Find cell with minimum entropy (fewest possibilities)
+        min_cell = min(possibilities.keys(), 
+                       key=lambda c: len(possibilities[c]))
+        x, y = min_cell
+        
+        # Choose random tile from possibilities
+        tile = random.choice(possibilities[min_cell])
+        grid.at((x, y)).tilesprite = tile
+        del possibilities[min_cell]
+        
+        # Update neighbor possibilities based on constraints
+        for dx, dy in [(-1, 0), (1, 0), (0, -1), (0, 1)]:
+            nx, ny = x + dx, y + dy
+            if (nx, ny) in possibilities:
+                # Filter based on placed tile's constraints
+                # (simplified - real WFC is more complex)
+                possibilities[(nx, ny)] = [t for t in possibilities[(nx, ny)]
+                                           if can_coexist(tile, t)]
+```
+
+See `src/scripts/cos_tiles.py` for the complete WFC implementation with:
+- 9-cell constraint matching
+- Special cardinal direction rules
+- Weighted tile selection
+- Multi-pass convergence
+
+---
+
+## Cellular Automata
+
+### Cave Generation
+
+Classic cellular automata for organic caves:
+
+```python
+import random
+
+def generate_cave(grid, fill_probability=0.45, iterations=5):
+    """Generate cave using cellular automata"""
+    w, h = grid.grid_size
+    
+    # Initialize with random noise
+    for x in range(w):
+        for y in range(h):
+            if random.random() < fill_probability:
+                grid.at((x, y)).walkable = False
+                grid.at((x, y)).tilesprite = 1  # Wall
+            else:
+                grid.at((x, y)).walkable = True
+                grid.at((x, y)).tilesprite = 0  # Floor
+    
+    # Iterate cellular automata rules
+    for _ in range(iterations):
+        next_state = []
+        for x in range(w):
+            for y in range(h):
+                # Count wall neighbors
+                wall_count = 0
+                for dx in [-1, 0, 1]:
+                    for dy in [-1, 0, 1]:
+                        if dx == 0 and dy == 0:
+                            continue
+                        nx, ny = x + dx, y + dy
+                        if nx < 0 or nx >= w or ny < 0 or ny >= h:
+                            wall_count += 1  # Out of bounds = wall
+                        elif not grid.at((nx, ny)).walkable:
+                            wall_count += 1
+                
+                # Apply rule: become wall if 5+ neighbors are walls
+                is_wall = wall_count >= 5
+                next_state.append((x, y, is_wall))
+        
+        # Apply next state
+        for x, y, is_wall in next_state:
+            grid.at((x, y)).walkable = not is_wall
+            grid.at((x, y)).tilesprite = 1 if is_wall else 0
+```
+
+### Smoothing and Refinement
+
+```python
+def remove_small_regions(grid, min_size=10):
+    """Flood-fill to remove disconnected small regions"""
+    w, h = grid.grid_size
+    visited = set()
+    
+    def flood_fill(x, y):
+        """Returns size of connected region"""
+        stack = [(x, y)]
+        region = []
+        while stack:
+            cx, cy = stack.pop()
+            if (cx, cy) in visited:
+                continue
+            if cx < 0 or cx >= w or cy < 0 or cy >= h:
+                continue
+            if not grid.at((cx, cy)).walkable:
+                continue
+            
+            visited.add((cx, cy))
+            region.append((cx, cy))
+            
+            # Add neighbors
+            stack.extend([(cx-1, cy), (cx+1, cy), (cx, cy-1), (cx, cy+1)])
+        
+        return region
+    
+    # Find all regions
+    regions = []
+    for x in range(w):
+        for y in range(h):
+            if (x, y) not in visited and grid.at((x, y)).walkable:
+                region = flood_fill(x, y)
+                regions.append(region)
+    
+    # Keep only largest region, fill others
+    if regions:
+        largest = max(regions, key=len)
+        for region in regions:
+            if len(region) < min_size:
+                for x, y in region:
+                    grid.at((x, y)).walkable = False
+                    grid.at((x, y)).tilesprite = 1
+```
+
+---
+
+## Noise-Based Terrain
+
+### Perlin/Simplex Noise
+
+Generate heightmaps for terrain:
+
+```python
+# Requires noise library: pip install noise
+import noise
+
+def generate_terrain(grid, scale=0.1, octaves=4):
+    """Generate terrain using Perlin noise"""
+    w, h = grid.grid_size
+    
+    for x in range(w):
+        for y in range(h):
+            # Sample noise
+            value = noise.pnoise2(x * scale, y * scale, 
+                                  octaves=octaves,
+                                  persistence=0.5,
+                                  lacunarity=2.0,
+                                  repeatx=w,
+                                  repeaty=h,
+                                  base=0)
+            
+            # Map to tile types (-1 to 1 -> 0 to N)
+            if value < -0.3:
+                tile = 2  # Water
+                walkable = False
+            elif value < 0.0:
+                tile = 0  # Grass
+                walkable = True
+            elif value < 0.3:
+                tile = 1  # Forest
+                walkable = True
+            else:
+                tile = 3  # Mountain
+                walkable = False
+            
+            cell = grid.at((x, y))
+            cell.tilesprite = tile
+            cell.walkable = walkable
+```
+
+---
+
+## Populating Generated Worlds
+
+### Entity Placement
+
+Place entities in generated content:
+
+```python
+def place_entities(grid, rooms, entity_density=0.05):
+    """Place enemies in rooms"""
+    for room in rooms:
+        room_area = room.w * room.h
+        num_entities = int(room_area * entity_density)
+        
+        for _ in range(num_entities):
+            # Random walkable position in room
+            x = random.randint(room.x, room.x + room.w - 1)
+            y = random.randint(room.y, room.y + room.h - 1)
+            
+            if grid.at((x, y)).walkable:
+                enemy = mcrfpy.Entity(
+                    grid_pos=(x, y),
+                    sprite_index=random.randint(10, 15)
+                )
+                grid.entities.append(enemy)
+
+def place_items(grid, rooms, num_items=10):
+    """Place items in random locations"""
+    placed = 0
+    attempts = 0
+    max_attempts = num_items * 10
+    
+    while placed < num_items and attempts < max_attempts:
+        # Random room
+        room = random.choice(rooms)
+        x = random.randint(room.x, room.x + room.w - 1)
+        y = random.randint(room.y, room.y + room.h - 1)
+        
+        if grid.at((x, y)).walkable:
+            item = mcrfpy.Entity(
+                grid_pos=(x, y),
+                sprite_index=random.randint(20, 25)
+            )
+            grid.entities.append(item)
+            placed += 1
+        
+        attempts += 1
+```
+
+---
+
+## Large World Generation
+
+### Chunk-Based Generation
+
+For worlds larger than memory allows:
+
+```python
+class ChunkManager:
+    """Generate chunks on-demand"""
+    def __init__(self, chunk_size=256):
+        self.chunk_size = chunk_size
+        self.loaded_chunks = {}  # (cx, cy) -> Grid
+    
+    def get_chunk(self, chunk_x, chunk_y):
+        """Load or generate chunk"""
+        key = (chunk_x, chunk_y)
+        if key not in self.loaded_chunks:
+            self.loaded_chunks[key] = self._generate_chunk(chunk_x, chunk_y)
+        return self.loaded_chunks[key]
+    
+    def _generate_chunk(self, cx, cy):
+        """Generate a single chunk"""
+        grid = mcrfpy.Grid(
+            grid_size=(self.chunk_size, self.chunk_size),
+            pos=(cx * self.chunk_size * 16, cy * self.chunk_size * 16),
+            size=(self.chunk_size * 16, self.chunk_size * 16)
+        )
+        
+        # Use chunk coordinates as seed for deterministic generation
+        seed = hash((cx, cy))
+        random.seed(seed)
+        
+        # Generate terrain for this chunk
+        generate_terrain(grid, scale=0.1)
+        
+        return grid
+    
+    def unload_distant_chunks(self, player_chunk, radius=2):
+        """Unload chunks far from player"""
+        px, py = player_chunk
+        to_unload = []
+        
+        for (cx, cy), chunk in self.loaded_chunks.items():
+            if abs(cx - px) > radius or abs(cy - py) > radius:
+                to_unload.append((cx, cy))
+        
+        for key in to_unload:
+            del self.loaded_chunks[key]
+```
+
+**Issue #123** and **Issue #67** track official subgrid and chunk stitching support.
+
+---
+
+## Performance Considerations
+
+### Batch Grid Updates
+
+Set many cells efficiently:
+
+```python
+# SLOW: Individual cell updates
+for x in range(100):
+    for y in range(100):
+        cell = grid.at((x, y))
+        cell.tilesprite = compute_tile(x, y)
+
+# FASTER: Minimize Python/C++ crossings
+tiles = []
+for x in range(100):
+    for y in range(100):
+        tiles.append(compute_tile(x, y))
+
+# Then set in batch (when batch API available - see [[Performance-and-Profiling]])
+for i, (x, y) in enumerate(coords):
+    grid.at((x, y)).tilesprite = tiles[i]
+```
+
+### Generation Timing
+
+Generate during scene transitions or in background:
+
+```python
+def start_generation():
+    """Begin procedural generation"""
+    mcrfpy.createScene("loading")
+    mcrfpy.setScene("loading")
+    
+    # Start generation timer
+    mcrfpy.setTimer("generate", generate_world, 10)
+
+def generate_world(ms):
+    """Generate incrementally"""
+    global generation_step
+    
+    if generation_step == 0:
+        rooms = generate_bsp_dungeon(grid)
+    elif generation_step == 1:
+        connect_rooms(grid, rooms)
+    elif generation_step == 2:
+        wfc_generate_tiles(grid)
+    elif generation_step == 3:
+        place_entities(grid)
+    else:
+        # Done!
+        mcrfpy.setScene("game")
+        mcrfpy.delTimer("generate")
+        return
+    
+    generation_step += 1
+```
+
+---
+
+## Examples and Demos
+
+### Complete Dungeon Generator
+
+```python
+import mcrfpy
+import random
+
+def create_procedural_dungeon():
+    """Complete dungeon generation pipeline"""
+    # Create grid
+    grid = mcrfpy.Grid(grid_size=(100, 100), pos=(0, 0), size=(1024, 768))
+    
+    # 1. Generate layout with BSP
+    rooms = generate_bsp_dungeon(grid, num_splits=4)
+    
+    # 2. Connect rooms
+    connect_rooms(grid, rooms)
+    
+    # 3. Tile placement with WFC
+    wfc_generate_tiles(grid)
+    
+    # 4. Smooth with cellular automata
+    smooth_edges(grid)
+    
+    # 5. Place player in first room
+    first_room = rooms[0]
+    player = mcrfpy.Entity(
+        grid_pos=(first_room.x + first_room.w // 2,
+                  first_room.y + first_room.h // 2),
+        sprite_index=1
+    )
+    grid.entities.append(player)
+    
+    # 6. Place enemies
+    place_entities(grid, rooms[1:], entity_density=0.05)
+    
+    # 7. Place exit in last room
+    last_room = rooms[-1]
+    exit_entity = mcrfpy.Entity(
+        grid_pos=(last_room.x + last_room.w // 2,
+                  last_room.y + last_room.h // 2),
+        sprite_index=99
+    )
+    grid.entities.append(exit_entity)
+    
+    return grid, player
+
+# Use it
+mcrfpy.createScene("game")
+mcrfpy.setScene("game")
+grid, player = create_procedural_dungeon()
+ui = mcrfpy.sceneUI("game")
+ui.append(grid)
+```
+
+See `src/scripts/cos_level.py` and `src/scripts/cos_tiles.py` for production examples from "Crypt of Sokoban."
+
+---
+
+## API Reference
+
+See [`docs/api_reference_dynamic.html`](../../src/branch/master/docs/api_reference_dynamic.html) for Grid and Entity APIs.
+
+**Key Grid Methods:**
+- `grid.at((x, y))` - Get cell for modification
+- `grid.grid_size` - Get dimensions
+- `grid.entities` - Entity collection
+
+**Key Cell Properties:**
+- `cell.tilesprite` - Tile index
+- `cell.walkable` - Pathfinding flag
+- `cell.color` - RGBA tint
+
+---
+
+**Navigation:**
+- [[Home]] - Documentation hub
+- [[Grid-System]] - Spatial container details
+- [[Entity-Management]] - Populating worlds with entities
+- [[AI-and-Pathfinding]] - Navigation in generated worlds