Dungeon Generation Algorithms: 4 Methods Explained

Dungeon generation algorithms are procedural techniques that create the layouts of caves, crypts, and ruins in video games. This article explains how four common methods—Random Walk, Cellular Automata, BSP Tree, and Room-and-Corridor—handle the task, from their core logic to their typical outputs. You’ll learn what each algorithm does, its strengths and weaknesses, and how to choose one for your project.

Formula

The calculator above estimates the total floor area generated by a room-and-corridor algorithm. It assumes each room is roughly rectangular with a width of 40% of the map width and a height of 30% of the map width. The formula is:

Total Area = Number of Rooms × (Map Width × 0.4) × (Map Width × 0.3)

Where:

• Number of Rooms – how many separate chambers you place.
• Map Width – the size of the grid in cells.
• Total Area – the sum of all room cells, in square cells.

This is a rough estimate; actual algorithms vary room sizes and may overlap.

Worked Example

Using the default values (10 rooms, 50-cell map):

1. Room width = 50 × 0.4 = 20 cells
2. Room height = 50 × 0.3 = 15 cells
3. Area per room = 20 × 15 = 300 cells²
4. Total area = 10 × 300 = 3000 cells²

The calculator returns 3000 cells², matching the formula.

Random Walk: The Drunken Path

The Random Walk algorithm simulates a creature wandering across a grid, carving out a path as it moves. Each step, the algorithm picks a random direction (up, down, left, right) and moves one cell, setting that cell to “floor�. This creates a single, winding tunnel that can branch if you occasionally start new walks from existing floor cells.

How it handles generation:

• Start at a random cell, mark it as floor.
• Repeat N times: move to a random neighbor, mark it as floor.
• Optional: with a small probability, start a new walk from a random floor cell to create branches.

The result is an organic, cave-like network with no clear rooms. It’s fast and simple, but can produce disconnected areas if the walk never revisits certain regions. Many roguelikes use this for “natural� caves, then add rooms manually.

Cellular Automata: The Cave Generator

Cellular Automata (CA) treats the map as a grid of cells that are either wall or floor. It starts with random noise (each cell has a ~45% chance of being floor), then applies a rule several times. The classic rule: if a cell has more than 4 wall neighbors, it becomes wall; otherwise it becomes floor.

How it handles generation:

1. Fill the grid randomly with walls and floors.
2. For each cell, count its 8 neighbors.
3. If neighbor walls > 4, set cell to wall; else set to floor.
4. Repeat steps 2-3 for 4-5 iterations.

This produces large, open caverns with jagged edges. The result is highly connected but often has isolated pockets. To fix that, you can run a flood-fill and remove small disconnected regions. CA is great for alien caves, mines, or underground biomes.

BSP Tree: The Structured Dungeon

Binary Space Partitioning (BSP) is a top-down approach. It recursively splits a rectangular area into two smaller rectangles, then continues splitting until each rectangle reaches a minimum size. Finally, it carves a room inside each leaf rectangle and connects them with corridors.

How it handles generation:

• Start with the whole map as a single rectangle.
• Split it randomly (horizontal or vertical) into two halves.
• Recursively split each half until the rectangles are small enough.
• For each leaf rectangle, place a room that fits inside.
• Connect rooms by linking each leaf to its sibling with a corridor.

BSP yields clean, rectangular rooms connected by straight or L-shaped corridors. It’s predictable and easy to control, making it ideal for dungeons, office buildings, or spaceship interiors. The downside: it can look repetitive if not varied.

Room-and-Corridor: The Classic Grid

This is the most common method in traditional roguelikes. It places a set of non-overlapping rooms randomly on the grid, then connects them with corridors. The algorithm usually works in two phases: room placement and connection.

How it handles generation:

1. Place rooms: pick a random position and size, check it doesn’t overlap existing rooms, then add it.
2. Connect rooms: for each new room, connect it to the previous room (or the nearest room) using an L-shaped corridor (first go horizontally, then vertically).
3. Optionally, add extra corridors to create loops.

The result is a classic dungeon with distinct rooms and winding hallways. It’s flexible—you can control room sizes, corridor widths, and connectivity. The main challenge is ensuring all rooms are reachable; using a “connect to previous� method guarantees a single connected network.

How to Choose the Right Algorithm

Your choice depends on the feel you want:

• Random Walk – for organic, maze-like caves with no distinct rooms.
• Cellular Automata – for large, open caverns with natural-looking edges.
• BSP Tree – for structured, rectangular rooms in a hierarchical layout.
• Room-and-Corridor – for classic dungeons with clear rooms and corridors.

Consider the gameplay: stealth games need corridors, exploration games need open spaces, and puzzle games need structured rooms. You can also mix methods—use CA for caves and BSP for castle interiors.

Common Problems and Fixes

Every algorithm has pitfalls:

• Disconnected areas – Use flood-fill to find unconnected regions and dig corridors to link them.
• Too many dead ends – Add loops by connecting random rooms after the main generation.
• Rooms too large or small – Clamp room sizes within a range and reject placements that exceed it.
• Corridors crossing rooms – Check corridor paths against existing rooms, or allow it for a more open feel.

Frequently Asked Questions

What is the simplest dungeon generation algorithm?

The Random Walk is the simplest to implement—just a loop that moves in random directions and carves floors. It’s great for quick prototypes but often needs extra steps to ensure connectivity.

Can I combine these algorithms?

Yes. Many games use a hybrid: start with Cellular Automata for caves, then overlay a BSP structure for a fortress. You can also use Random Walk to connect rooms from a Room-and-Corridor generator.

How do I ensure the dungeon is fully connected?

After generation, run a flood-fill from a random floor cell. If any floor cells are unreachable, dig a corridor from the main region to the isolated one. Repeat until all are connected.

Do these algorithms work for 3D dungeons?

They can be adapted. For 3D, you often generate a 2D layout and then extrude it vertically, or use a 3D grid with similar rules. BSP works well for multi-level dungeons by splitting in 3D.

What is the performance cost?

All four are fast for typical map sizes (under 100×100). Cellular Automata is O(iterations × cells), while BSP and Room-and-Corridor are O(rooms). They run in milliseconds, so they’re suitable for real-time generation.

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in t | Number of rooms | - | 10 | 1
in d | Map width | cells | 50 | 10
out area | Total room area | cells² | t * (d * 0.4) * (d * 0.3) | 0