Yudha’s Starmap

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An interactive procedural galaxy generator built in JavaScript. It creates explorable 3D universes filled with stars, planets, and fledgling civilizations, running entirely in your browser.

I originally wrote the base logic in R back in 2020, then made several attempts to migrate it to JavaScript. The project was intended for use in The Salvage Crew and Pilgrim Machines — I wanted a galaxy generator that felt plausible rather than arbitrary. I ended up not using it directly in the books; at the end of the day, the real galaxy is more interesting than anything I could generate. The current version was rebuilt for a 2025 University of Bergen keynote presentation, and now features stars, planets, and civilizations.

How it works

The core idea: define rules for star formation, planetary orbits, and habitability, and let procedural generation fill in the specifics through rulesets and constrained randomness. Design inspiration comes from Stellaris, Endless Space II, and Sins of a Solar Empire, plus various astronomical references for the underlying distributions.

Stars — mass determines temperature, luminosity, spectral type, size, and evolutionary stage.

Planets — type is determined by orbital distance and star properties; additional attributes include size, mass, gravity, composition, atmosphere, temperature, water presence, moons, rings, and habitability.

Civilizations — traits, government types, and tech levels assigned probabilistically on habitable worlds. The interesting part is what emerges from the interactions: populated clusters, isolated systems, hostile neighbours, chains of habitable worlds that no one has reached yet.

Features

Parameterized generation — control galaxy shape (Spiral, Elliptical, Irregular), star count, and civilization emergence probability via UI
3D interactive visualization — powered by 3d-force-graph and Three.js; click, drag, explore
Layered dependencies — each generation step builds on the last, so complexity accumulates naturally
Export — generated universes can be saved; import planned for a future version

Running it

Clone or download the repository
Place all files in the same directory
Open index.html in a modern browser (Chrome, Firefox, or Edge)
Use the bottom-right panel to generate and explore

An internet connection is needed for the external libraries.

Code structure

galaxy-core.js — base constants and utility functions
galaxy-classes.js — core generation logic for Star, Planet, and Civilization classes
galaxy-generator.js — orchestration of the generation process
galaxy-visualization.js — data-to-visual mapping and rendering
galaxy-ui.js — user input handling and panel updates