Generate a Map

Use Mimir’s mapgen tool to procedurally generate Dungeondraft-format maps from biome presets or custom YAML configurations.

What Mapgen Creates

Mapgen generates .dungeondraft_map files containing:

• Noise-based terrain with blended textures
• Trees, grass, and other vegetation
• Roads and rivers that follow the terrain
• Rooms with walls, doors, and windows
• Water bodies, elevation contours, and lighting
• Polygon-based layouts for irregular room shapes

Output files open directly in Dungeondraft for further editing or UVTT export. Mimir cannot open .dungeondraft_map files directly — to use a generated map in Mimir, open it in Dungeondraft (a paid tool) and export it as Universal VTT.

Quick Start: Using a Preset

Prerequisite: the mimir-mapgen binary is not bundled with the Mimir app. Either download a pre-built binary from GitHub Releases (attached to each release for every platform) or build it from source with cargo build -p mimir-mapgen --release. See Install and Use Mapgen as a Standalone Tool for details.

Generate a map from one of 12 built-in biome presets:

mimir-mapgen generate --preset forest --output my-forest.dungeondraft_map

Use a specific seed for reproducible results:

mimir-mapgen generate --preset forest --seed 42 --output my-forest.dungeondraft_map

List Available Presets

mimir-mapgen list-presets

Example presets:

Preset	Size	Description
forest	32x32	Dense temperate forest with dirt paths, scattered rocks, and natural clearings
cave	24x24	Underground cavern with rocky terrain and dark ambient lighting
forest_river	32x32	Dense forest bisected by a meandering river with rocky banks

See the Mapgen Reference for the full table of all 12 presets and their aliases.

Custom YAML Configs

For full control, write a YAML configuration file:

name: "Forest Clearing"
width: 32
height: 32
seed: 42

terrain:
  slots:
    - texture: "res://textures/terrain/terrain_grass.png"
      lower: 0.0
      upper: 0.5
    - texture: "res://textures/terrain/terrain_dirt.png"
      lower: 0.4
      upper: 0.7
    - texture: "res://textures/terrain/terrain_stone.png"
      lower: 0.6
      upper: 0.9
    - texture: "res://textures/terrain/terrain_gravel.png"
      lower: 0.8
      upper: 1.0
  blend_width: 0.05
  smooth_blending: true

trees:
  - tree:
      textures:
        - "res://textures/objects/more_trees/oak_01.png"
        - "res://textures/objects/more_trees/oak_02.png"
      min_distance: 500.0
      noise_lower: 0.4
      noise_upper: 0.75
      probability: 0.5
      scale_min: 0.8
      scale_max: 1.2
      layer: 300
      random_rotation: true
      random_mirror: true

roads:
  - {}

Generate from the config:

mimir-mapgen generate config.yaml --output clearing.dungeondraft_map

Validate a Config

Check a config for errors without generating:

mimir-mapgen validate config.yaml

Iterating on Maps

Maps are deterministic — the same seed and config produce the same map. To iterate:

1. Generate with a specific seed
2. Open in Dungeondraft and review
3. Adjust config parameters
4. Regenerate with the same seed to compare changes
5. Try different seeds for different terrain layouts

Using via AI Assistant

Mapgen is also available as an MCP tool (generate_map) through Mimir’s AI assistant integration. Describe the scene you want — “a misty forest clearing with a road” — and the assistant will build the YAML config and generate the map for you.

See Also

• Install and Use Mapgen as a Standalone Tool — Installation and a full worked example
• Upload a Map — Import maps into Mimir modules (UVTT or image files)
• Mapgen Reference — Full YAML schema and configuration details