PBE Games : Ground Rules

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Ground Rules Generator

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Terrain Wild Locale Civilized Locale Features Special Results

Ground Rules - Instructions

Ground Rules is a terrain generator for RPG hex maps. It creates area by area descriptions of hexes that include terrain, roads, rivers, settlements, and encounter sites. Ground Rules can be used to run a sandbox-style hex-crawl campaign, inspire campaign maps, or for solo play. Ground Rules assumes a fairly small hex size, the classic six mile hex is ideal.

To use Ground Rules you'll need some means of recording hex entries, ideally a paper or electronic hex map. As you build your map you'll be recording each terrain's contents, as well as a terrain code that's used to generate neighboring hexes. The basic process for generating a hex is easy. Each button in the grid above represents a table used to generate part of a hex entry. To use the tables:

  1. Select a Terrain table from the first column using these guidelines:
    • Pick the most frequently appearing terrain code (A1-A7) from the surrounding hexes. In case of ties use the lowest value code, i.e. if there are two A4 hexes and two A2 hexes, use A2.
    • If there are no generated neighboring hexes, use code A1.
    • Click the button and record the results on your map. Be sure you record the terrain code, as you'll need it for the next step and nearby hexes.
  2. Click a button in either the Wild or Civilized Locale column with the numeric value equal to that of your newly generated terrain. Wild results have fewer roads and settlements, but more sites than Civilized lands. For example if your terrain result was A4 Forest, click either B4 or C4. Record the result.
  3. Follow any additional instructions included in the result. This may include rolling on Features or Special Results tables to fill out details on the hex.
  4. If you'd like to add more special features to your map, just roll on the appropriate Features table and add the result to your map.
  5. Select a new hex to generate and start the process over.

The most important rule: random systems are never perfect, especially when it comes to generating things like roads and rivers. Your judgement should always prevail over the dice. If you don't like a roll, ignore it or generate a new result.

Some feature-specific directions will ask you to roll dice to determine additional features of a particular hex. For your convenience a series of dice rolls are appended to each generated result. You can use these results or roll your own dice as you like.

Roads and Rivers

Direction Indicators

Roads and rivers, collectively called paths, are hard to get right with a random system. Here are some rules and guidelines for handling paths using this generator.

  • Always try to connect up rivers and roads with existing paths. This reduces the overall number of paths, and keeps things a bit more sensible.
  • When you first create a new path, generate a few hexes along its route to see where it goes.
  • Roads end at settlements and some sites (abandoned settlements, dungeons, and similar places).
  • Roads also start at settlements and sites, so if there's a new road indicated, see if it makes sense to connect it to a nearby location.
  • Rivers run downhill. If there's no downhill exit, place a static body of water, lake, pond, or ocean, instead.

Directions for roads and rivers (collectively, paths) are given as an entry point plus a route. Together they describe where the path start and ends. The illustration at right shows how to interpret these directions, depending on how you draw your paths and which hex orientation you use.

Directions have an entry point, which can be matched to corners or faces in the images. They also instruct you to count spaces. If your path runs along edges, begin at the hex corner that matches the given direction and count corners. The path exits at the last corner counted. If your path runs through hex faces, begin at the face that matches the given direction and count faces. The path exits the last face counted.

Hint: Draw rivers on edges and roads through faces for a clean-looking map.

Placing Hexes

Coastline, Shoreline, and some terrain features will ask you to place hexes of a specific type nearby. Common sense should prevail. If there are no empty spaces, or no locations that make sense, feel free to ignore these directives.

Be sure you note the terrain code for each placed hex. You should also generate a Locale entry using that code to see if there are any special features in the new hex.


Coastline marks a transition from land to ocean terrain. If the generator produces a Coastline result, do the following:

  • Place a temporary marker on the hex to mark it as Coastline.
  • Place two Ocean A2 hexes adjacent to the Coastline hex.
  • Reroll the Coastline hex, ignoring terrain code A2 when choosing a Terrain table, and discarding any Ocean results.
  • Be sure you roll a Locale result for each Ocean hex too.


Shoreline is the reverse of Coastline, marking a transition from ocean to land. If the generator produces a Shoreline result, do the following:

  • Place a temporary marker on the hex to mark it as Shoreline.
  • Mark two additional non-consecutive hexes as Shoreline as well.
  • Reroll each marked Shoreline hex, ignoring terrain code A2 when choosing a Terrain table and discarding any Ocean results.
  • Be sure you roll a Locale result for each Shoreline hex too.


Here are a few ways to change up how you use tables.

  • Subdividing Hexes - If you're subdividing and mapping a larger scale hex with fixed terrain using Ground Rules, you can get more consistent terrain results, by recording any A1 terrain code normally, but rolling on the table that best matches the larger hex's base terrain whenever you would normally roll on A1. For example if your large hex is plains terrain, roll any A1 hex as A3 instead.
  • True Wilderness - Treat any Settlement result as a Site instead, using the Extras entry, or rerolling as needed. Ignore all Roads results.

Ground Rules version 1.0