Procedural dungeon generation is one of the most powerful techniques used in roguelikes, RPGs, and survival games.
Instead of designing every level manually, the game generates new layouts automatically using algorithms and rules.

In this guide, we will build a rule‑based dungeon generator in Unity where rooms connect only when their constraints match.
This approach creates believable layouts while preventing impossible connections.

1. What is a Rule‑Based Dungeon Generator?

A rule‑based dungeon generator uses predefined room modules combined with logical constraints.
Each room defines where connections can exist and what types of rooms can connect to it.

Example rules:

• A boss room can only appear at the end of the dungeon
• A treasure room must connect to a corridor
• A corridor must connect to at least two rooms
• The dungeon must contain exactly one start room

Instead of random chaos, the generator builds a layout that respects these rules.

2. Designing Modular Room Prefabs

Each dungeon piece is a prefab containing connection points.

Typical room types:

• Start Room
• Corridor
• Combat Room
• Treasure Room
• Boss Room

Each room prefab should include:

• Door sockets
• Room type metadata
• Spawn markers

3. Creating a Room Metadata Script

Each room prefab needs a component describing its properties.

using UnityEngine;

public enum RoomType
{
    Start,
    Corridor,
    Combat,
    Treasure,
    Boss
}

public class DungeonRoom : MonoBehaviour
{
    public RoomType roomType;
    public Transform[] doorPoints;
}

This script lets the generator understand how rooms connect.

4. Dungeon Layout Generation

A simple way to build a dungeon is using a graph expansion approach:

1. Spawn the start room
2. Pick a door
3. Select a compatible room type
4. Attach it to the door
5. Repeat until the dungeon size is reached

5. Basic Dungeon Generator Script

using UnityEngine;
using System.Collections.Generic;

public class DungeonGenerator : MonoBehaviour
{
    public DungeonRoom startRoom;
    public List<DungeonRoom> roomPrefabs;

    public int dungeonSize = 10;

    private List<DungeonRoom> spawnedRooms = new List<DungeonRoom>();

    void Start()
    {
        GenerateDungeon();
    }

    void GenerateDungeon()
    {
        DungeonRoom first = Instantiate(startRoom, Vector3.zero, Quaternion.identity);
        spawnedRooms.Add(first);

        Queue<Transform> openDoors = new Queue<Transform>();

        foreach (var door in first.doorPoints)
            openDoors.Enqueue(door);

        while (spawnedRooms.Count < dungeonSize && openDoors.Count > 0)
        {
            Transform door = openDoors.Dequeue();

            DungeonRoom newRoom = GetRandomRoom();

            DungeonRoom roomInstance =
                Instantiate(newRoom, door.position, door.rotation);

            spawnedRooms.Add(roomInstance);

            foreach (var newDoor in roomInstance.doorPoints)
                openDoors.Enqueue(newDoor);
        }
    }

    DungeonRoom GetRandomRoom()
    {
        int index = Random.Range(0, roomPrefabs.Count);
        return roomPrefabs[index];
    }
}

6. Adding Rule Constraints

To prevent broken layouts, we add rules before placing a room.

Examples:

• Only one boss room allowed
• Treasure rooms cannot connect directly to start rooms
• Boss room must appear after a minimum number of rooms

Example rule validation:

bool IsValidRoom(RoomType type)
{
    if(type == RoomType.Boss && spawnedRooms.Count < 6)
        return false;

    if(type == RoomType.Start)
        return false;

    return true;
}

7. Avoiding Room Overlaps

When placing rooms randomly, overlaps may occur.
A common solution is using collision checks before finalizing placement.

bool IsSpaceFree(Vector3 position, float radius)
{
    return !Physics.CheckSphere(position, radius);
}

8. Improving the Generator

Professional dungeon generators add additional systems:

• Weighted room probabilities
• Guaranteed key rooms
• Branching paths
• Loop connections
• Secret rooms

These systems turn simple random layouts into designed gameplay experiences.

9. Advanced Generation Techniques

Large games use more sophisticated algorithms such as:

• Graph‑based dungeon generation
• Wave Function Collapse
• Cellular automata
• Binary space partitioning
• Constraint satisfaction systems

Each technique produces different styles of procedural worlds.

Conclusion

Rule‑based procedural dungeon generation allows developers to create infinite gameplay spaces while maintaining design control.
By combining modular prefabs, logical constraints, and smart placement algorithms, you can generate dungeons that feel handcrafted while remaining fully procedural.