Design concepts

A DungeonMaker design does not draw a dungeon. It sets up a small population of agents and lets them dig. This page explains the ideas in our own words; the original description is the manual of DungeonMaker 2.05 by Peter Henningsen (DM2_Manual, shipped with the upstream release). Every term below links to the section of the design config reference that lists its fields.

Two kinds of ground

A map starts as one big block of open or closed ground (background in the map section) and gets pre-placed shapes: rectangles of guaranteed-open or guaranteed-closed cells, room outlines, doors, and openings in the map border. Everything the designer wants to be exactly where it is goes here, for example the room of a story character.

The generator then builds around these shapes with two families of builders. Where the ground is open, crawlers raise walls and produce a labyrinth. Where the ground is closed, tunnelers carve passages and rooms and produce a dungeon. The two areas are called labyrinth and dungeon throughout the rest of the design, for room counts and for entity placement.

Crawlers

A crawler walks across open ground and leaves a wall behind it. Three numbers dominate how its labyrinth looks:

• the corridor width, the space it keeps between its wall and other closed cells,
• the step length, how many cells it walls up per step,
• the chance to change direction at the end of a step.

Corridor width and step length are set per generation, the direction chance is inherited from the parent with a little random mutation. That mix lets one map have regions with different character (inherited genes follow the ancestors of a region) while generations stay compatible with each other (per-generation values). The lists live in crawlers.

Crawlers enter the map in three ways: as design crawlers placed at a fixed position, as random crawlers that start at the map border at a configured density, or as offspring of other crawlers. Offspring and random crawlers are always open: they leave a gap at the end of their run, so a crawler never cuts off a part of the labyrinth, and everything stays reachable. A design crawler can be closed on purpose, to block a passage and force a path through a certain room.

Tunnelers and roomies

Tunnelers are the more complex builders. A tunnel can have any odd width, so tunnelers carry a width that their children may grow or shrink by probability. They can also carve anterooms, small meeting places, most often in front of rooms or where tunnels intersect, and they spawn roomies: builders that make at most one step. A roomie looks for enough closed ground for the room size it wants and excavates the whole room at once, or it removes itself.

Usually one design tunneler starts at each entrance into a closed area and at each door of a pre-placed room. Tunnelers like to join existing passages and to break into rooms, but nothing guarantees that two tunnel systems meet. Whoever uses the dungeon should test the connectivity that matters (entrance to exit) and pick another seed if the test fails. The fields are in tunnelers; sizes, counts and aspect ratios of the rooms are in rooms.

Generations and spawn delay

Every builder belongs to a generation. Generation N starts only after generation N-1 has died out. A builder dies when it runs out of space or reaches its maximum age; in between it takes steps, which build a stretch of wall or tunnel, maybe turn, and maybe spawn one or two children.

Because early generations fill the map first, when children appear decides what the map looks like. spawnDelay holds, for crawlers, roomies and tunnelers, eleven percentages that say how many generations after its parent a child is born. The values sum to 100. Tunnelers that dig wider tunnels than their parent have their own delay in tunnelers, because wide tunnels should start far from the entrance.

Behaviour that applies to all

behaviour holds the settings every builder shares: the mutation strength that changes inherited values between generations, the chance that a builder ignores its intended heading, and the patience that decides how late (or whether) rooms get built in the dungeon area.

After the builders

When all builders are done the generator can find places in the open labyrinth that become a room by closing a single door, and can place monsters and treasure. The upstream author calls the monster and treasure placement a generic demonstration that every game has to adapt, which is why it is an optional layer in this package: see Output layers and population.

Why a design reads like a recipe

The designer does not control individual cells. He or she controls probabilities, widths and timing, and then watches. The Playground replays the construction step by step, which is the quickest way to develop a feeling for these parameters, as the upstream manual also recommends: roll the seed again and again and look at what stays the same and what changes. For orientation of the coordinates and the meaning of cell values see Orientation and cell values.