Generate fantasy world maps using fractal great-circle fault lines.
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Olsson World Generator – Help & Guide
This tool generates random fractal world maps using John Olsson's great-circle fault line algorithm (1999). Below is a guide to every field and feature:
Percent Water (0–100): Controls the ratio of ocean to land. Higher values flood more terrain into oceans; lower values produce larger continents.
Percent Ice (0–100): Determines the extent of polar ice caps generated via floodfill from the poles.
Height of Image (100–2048): Sets the canvas height in pixels. Higher resolutions produce more detailed maps and automatically scale iteration density.
Projection: Choose between Square (equirectangular), Mercator, Spherical (3D globe), Orthographic NP (North Pole centered), or Orthographic SP (South Pole centered).
Scroll / Rotate Degrees (-360 to 360): Shifts longitude horizontally for flat maps or rotates the 3D globe view.
Colors: Selects the rendering palette: Terrain & Snow (default, with blue oceans, green-to-brown rocks, and snow peaks), Green/Blue, Olsson Original, Twelve Colors, or Two Colors.
Random Seed: PRNG seed value. Entering a number reproduces an exact map; leaving it blank generates a new random map on each click.
Lock Seed (Off / On): When set to On, captures and displays the active random seed in the seed field so you can keep or share it.
Iterations (1–5000): The number of tectonic fault-line passes that uplift and depress continental plates.
Smoothing Range (0–100): Applies separable neighbor elevation averaging to smooth jagged fault lines.
Generate Map: Runs the simulation and renders the map onto the canvas.
Download Map (PNG): Appears after generation; saves the rendered map canvas as a PNG image file.
Help: Opens this modal guide.
The algorithm used by this generator was ported from C code written by John Olsson in 1999 and updated much later by the donjon site. The source code for this plugin is available at https://github.com/leonatkinson/olsson-world under a GPLv3 license.
