VELLUM

About Vellum

What is Vellum?

Vellum is a procedural cartography engine. Give it a number, a "seed," and it invents an entire world (terrain, rivers, forests, towns, and their names) and draws it as an old-fashioned atlas chart.

Is this AI image generation?

No. There is no machine learning or image model involved. Vellum follows a fixed set of rules (layered noise, a water-flow simulation, and name grammars), so it draws crisp, infinitely scalable SVG maps, and the same seed always produces exactly the same one.

What is a "seed"?

A seed is a number that serves as a world's identity. Seed 42 always draws the same island; change the number for a different world. It is printed in every chart's margin, so you can always find your way back to a map you liked.

Do I need to install anything to try it?

No. The Explorer runs the whole engine in your browser. Type a seed and draw; nothing is uploaded. To generate files on your own machine, clone the repo (see the README).

Can I use the maps I make?

Yes, freely. Maps you generate with Vellum are yours to use for anything, including commercial work, with no restrictions and no attribution required (they are dedicated to the public domain). The Vellum source code itself is released under the MIT license, so you are welcome to build on the engine too.

Why "Vellum"?

Vellum is the prepared animal skin that real medieval maps and manuscripts were drawn on, a fitting surface for charts of places that were never real.

How a world is built

How is the land shaped?

Layered "noise" produces a field of elevations. A sea level is then chosen so that the intended fraction of the map is land, and everything above the waterline becomes the coastline, hills, and mountains.

How do the rivers and lakes form?

Vellum simulates water. Rainfall runs downhill along the steepest path, and the algorithm guarantees every drop can reach the sea, so rivers always connect and flow the right way, widening toward their mouths. Where water collects below sea level inland, you get a lake.

Where do the towns, roads, and borders come from?

Towns are scored by good harbors, river mouths, and flat, fertile land. Roads are the cheapest paths between them, and they reuse one another, so shared trunk roads emerge naturally. Realms are formed by giving each capital the land nearest to it, with borders that prefer to follow rivers and ridgelines.

Do the settlements have a history?

Yes. After the world is built, Vellum simulates a rough history: towns receive founding dates, and some villages fall into ruin before the survey is drawn. Ruins appear on the map as a broken-tower glyph with a dimmed label. The atlas adds a Chronicle section, a dated record of founding events and collapses, and the gazetteer notes cite dates where relevant ("founded in the year 312; fell to ruin by 581").

Is every map really repeatable?

Yes. Every random choice descends from the seed, so the same seed with the same options always draws an identical map.

Names & invented languages

Where do the names come from?

Every world picks one of six invented cultures, each with its own sound, and uses it for everything: towns, rivers, peaks, seas, and realms. Because a single map keeps to one culture, its names share a family resemblance, the way place names within one country do. Nothing is taken from a real word list; every name is built from scratch.

How does the name "grammar" work?

In two steps. First Vellum builds a bare stem by stringing together a culture's sound pieces: beginnings like "mar" or "dr," vowels like "a" or "ai," and endings like "nd" or "mor," following that culture's syllable patterns. Then it wraps the stem in a template to fit the feature, for example "The Sea of ___," "Mount ___," or a town ending such as "haven." A few tidy-up rules keep each name short and pronounceable, and no two names on one map repeat.

What are the six cultures?

Each is a different sound-world, loosely echoing a real one: a soft seafaring tongue, a hard northern one, a desert tongue rich in "sh" and "kh," an airy woodland one, an open island one heavy with vowels, and a harsh mountain one full of clusters. The chart's title page even credits an invented surveyor whose name comes from the same culture.

Do these names fill the gazetteer too?

Yes. The gazetteer, the atlas's directory of every town, lists them by these same invented names, grouped by realm, with a line or two of travelers' notes written in the same spirit. The labels on the map and the entries in the gazetteer come from one and the same source.

Climate, styles & map types

How does climate change the look?

Climate sets temperature, which sets the biomes, and biomes change the map's symbols, not its base color. A polar world shows pine woods and open tundra, with the snow line low on the hills. A tropical world shows palms, deserts marked with dunes, and snow only on the highest peaks. Temperate sits between, with broadleaf woods. The coastline of a given seed is identical in every climate.

So is a polar map white?

No, and that surprises people. The land is the same parchment (or elevation tint) in every climate; "cold" shows through the tree types, the beaches, the snow line, and the gazetteer's notes, not a change of palette.

What are the four styles?

Antique: parchment, hatched mountains, sea monsters. Topographic: elevation tints and contour lines. Ink: pen-and-ink monochrome. Nautical: a sea chart with depth soundings, prevailing-wind arrows, and ocean-current streamlines. (The nautical style draws no land symbols, so climate is most muted there.)

How do I read the symbols and labels?

Most charts carry a small key in one corner that names the symbols actually on that map: the settlement marks, the terrain glyphs, rivers, and on sea charts the depth soundings and wind arrows. The lettering is a code too. Bold capitals mark a capital city, plain type a town or village, faded spaced capitals name a realm, and italics name water (seas, rivers, and lakes) and forests. Every atlas page carries a key, and you can turn one on for any chart you draw in the Explorer or generate locally.

What do the colors on an antique chart mean?

Less than you might expect, because an antique chart shows most things by drawing rather than by color. The land is a single even parchment, the same cream at every elevation and in every climate; mountains are drawn as brown hatched ranges and forests as little tree marks, not painted on. The sea is a pale sage green, ringed by slightly darker "waterlines" that echo each coast in the old engraved manner. A dark brown line is the shoreline, thin blue lines are rivers, and faint brown lines are roads. The one place color really carries meaning is the soft washes of red, green, gold, blue, and mauve: each marks a realm, one tint apiece, so you can tell neighboring territories apart. Those are political regions, not terrain, so a single-realm island shows almost none while a continent of several realms shows them clearly. (Topographic charts are the exception: there the land color itself maps to elevation.)

What are the map types?

Island (one landmass), archipelago (scattered isles), continent (a large landmass), and city-state (one dominant free city and its hinterland). Leave it unset and the seed chooses.

Making & reproducing maps

How do I make a map on my own machine?

Download the source from GitHub and follow the setup instructions in the README. Charts are generated as SVG files you can open in any browser.

I found a map I love. How do I get it back?

Note its seed (printed in the margin) and enter it again. One catch: if you chose a specific type, climate, or land amount, those aren't saved on the chart itself, so you'll need to set them the same way again alongside the seed.

Can I make a high-resolution print?

Yes, if you have the source installed locally. The poster command draws an oversized chart (about 14 inches at 300 dpi) and saves it as a PNG, ready to print as wall art. See the README for details.

What is the Seed of the Day?

The Seed of the Day page draws a new world each day automatically. The seed is today's date in UTC read as a number (for example, June 22 2026 becomes seed 20260622), so everyone in the world sees the same chart on the same day. No reload needed: the page renders fresh in your browser each time you visit.

What is the atlas?

The atlas binds one world into a small book: the chart in several styles, four thematic data plates (vegetation, temperature, rainfall, and population), two regional close-ups that zoom in on busy areas, a coat-of-arms plate for every realm, a Chronicle of the world's founding events and ruins, and a gazetteer of every town with travelers' notes. You can generate one from the Explorer, or locally from the command line (see the README).

What is the gallery?

The gallery is a contact sheet of many worlds at once, useful for browsing seeds until one catches your eye.