Tuesday, November 10, 2020

Voronoi Diagrams and the City Crawl

I tend to prefer using Voronoi Tesselations/Diagrams for my Urban Adventures/City Crawls instead of the traditional Grids or Hex Maps. They just feel more organic to me, and can really capture how sometimes it takes longer to move from one dense/crowded/difficulty planned area to another. Distances are seldom in a straight line in Cities, and it's easy to get turned around or lost in an unfamiliar Urban Center without a Guide. I dislike relying as much on measuring out precise distances these days, instead preferring to think of navigating Cities more in terms of resource consumption and procedural checks.

Unlike in a Standard Dungeon, Food/Water/Light should be relatively easy or at hand (provided the characters are not utterly destitute) so the resources we’re dealing with are generally TIME and MONEY. TIME to meet deadlines assocaited with hooks/rumors/adventure, and MONEY paid to Guides or for Information to reduce TIME. As the old adage goes: They are often one in the same. Also throwing another wrench in the works are Produral Checks: Bad Weather, Encounters, and other unusual Events that can breathe life into an area (a neighborhood wide Celebration clogging the streets, Hue and Cry from a Crime udnerway, etc.)

Here’s a quick way to generate a Voronoi City Map for a Crawl that produces something like this:

First, locate a map you like or create one. The example above uses this twitter account: https://twitter.com/metropologeny

(you can generally right click on an image here, and “Open in a New Tab” to obtain a URL to use in the next step).

Next, go here: http://cfbrasz.github.io/Voronoi.html

Paste the URL from the twitter account in the “Display Image with URL” box. Then, if you prefer, you can use your mouse to place points and divide the map into districts/neighborhoods/sections/quarters, or if your lazy, you can uncheck the “Update diagram on mouse move” check box, and then place a number in the Add box and click Generate until you see something that looks interesting or usable.

I like going with “20” sites, for ease of randomization with our handy, ubiquitous icosahedron, but for sparser/denser maps other site amounts might work a little better.

And there you have it: Fairly quick Voronoi City Crawl Map!

You can number the sites (those dots make them a little easier to identify), whip together some Exciting/Evocative Smells, some interesting NPCs with Professions that can help you intuit the primary shops or industry of an area, or perhaps a City Dweller Event as a “hook” or ongoing item of interest, and tailor a few Encounter/Event Tables to the different regions to give it some real flavor and flair. You could even stock them like Dungeon Rooms (Encounter, Hazard, Treasure, etc.) with some judicious reskinning.

I am very tempted to start working on a few more Tables that can help with Urban Crawls. One can never have enough random inspiration to cut down on tedious preparation!


  1. This is a great walk through - thanks for sharing your flow! I was not aware of Metropologeny before - that alone was worth the price of admission.
    I would be interested to know what scale do you normally work to with this - for a whole city, for select districts of interest within a larger map you are using?

    1. With a splash of color to indicate water, the above could really be the "Port Quadrant" of a much larger Metropolis :).
      I've done much larger and dense ones before for certain campaigns that are going to be very "City-centric."
      But in terms of granularity, I generally only focus on the portions of a truly large City where the players have indicated they are interested in exploring. I might have a larger "map" or idea of the rest of the City, but if it's not going to be important in play, then I try to minimize the preparation I do so that the element of discovery remains for both me and the other players. I'll generally have key things nailed down at least (like Government/Factions, Exports, Sweeping Conflicts, etc.) because they can have an overall impact on the "character" but it's better to have broad strokes on those things until the camera zooms in.




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