Cartesian Hex Map Notation, Hexcrawls and Procedurally Generated Worlds

Illustrated above is a portion of the process in action. 

The idea here is that the world only exists where the PC's have discovered it by going somewhere. Essentially there is no world-building and the narrative is emergent from the dice rolling. The necessary preparations from the Referee for such a hex crawl would consist of creating dungeons, wandering monster tables, and little else.

Alternative Hex Notation

The starting dungeon, town, and road is at Hex with Coordinates 0,0

The other hexes are then labeled based on their position relative to the central starting hex

We can then keep expanding the labels outward and we see a few axis emerge

Or we can simply look at the the outermost edges of the hex map and simply apply the coordinates there.

This allows you to start in the center of a hex map and build outwards rather than filling out a hex map based on the top corner being 0,0. What lies outside the starting town is then almost entirely procedurally generated by rolling as a party travels outside of some predetermined set pieces (these can be dungeons, towns, or anything else you have made in advance).

Set Piece Placement

For every edge from the starting Hex in a clockwise manner starting at the top you roll a 1d6 which corresponds to a set piece (illustrated below). That set pieces's distance is then rolled for.

Author's Notes: This is an example of how to place set pieces based on my current "setting" . At some point soon I will detail each so you can use them as set pieces for your own games. Predetermined Set Pieces from which the Outlander's Come 1. (1d6+10 hexes away) Valley of the Nalil and (1d6+14 hexes past that Location) the Empire of the Alabaster Crown 2. (1d6+4 hexes away) City With Port and Sea Adjacent to the Whirling Straight 3. (1d6+8 hexes away) Sodden Land of the Hallamites 4. (1d6+6 hexes away) Dark City of Ozborn 5. (1d6+12 hexes away) Starving Lands Surrounding Lymos 6. (1d6+8 hexes away) City with Port and Sea Adjacent to the Debtors Passage More Set Pieces 1. The Vast Despair and Wayland's Hole Within: 8 Hexes past the Sodden Land of the Hallamites 2. Vile Castle Blue: 7 Hexes in the same edge direction as the City with Port and Sea Adjacent to the Debtors Passage 3. Waystation Medusa: 3 hexes out to sea past the Whirling Straight Sea Port 4. Spore Pits of Hooded Shambler: 8 Hexes towards the Valley of the Nalil 5. Giant Masks Complex: 3 Hexes away from the Dark City of Ozborn in a random edge direction 6. Canticile, the Friendless Refuge: 13 Hexes in the same edge direction as the Starving Lands Surrounding Lymos

Procedurally Generated World Mechanics

1. Hex Contents

Hex contents are based on the state of the Hex if it's in Polite Lands (within 2 hexes of a large settlement [city or town]) or otherwise in the wilderness. Polite Lands hexes have a 1/4 chance of being filled while wilderness hexes have a 1/8 chance of being filled.

Polite Lands Hex Contents (1d20)

1-8	Polite Lands Road (1d8 hexes long)
9-15	Village
16-17	Fortified Keep
18-20	Ruins (either a dungeon or just signs of civilizations past)

Wilderness Hex Contents (1d20)

1-11	Polite Lands Road (1d8 hexes long)
12-15	Road to a Town (2d6 hexes long)
16-17	Road to a City (2d8 hexes long)
18-20	Ruins (either a dungeon or just signs of civilizations past)

(Secret Hex Contents are rolled for when a party travels through a hex and only exist after they have been found)

2. Roads

Roads are a special case its pathway has to be generated. When a party stumbles upon a road it's entire length is to be generated at once. Polite Lands Roads need to have both of their destination rolled for, while any other road already has one of it's destinations decided and simply rolls once as if it were a Polite Land Road for its other destination. As a road is generated all of the terrain it passes through is generated as well as the terrain of it's destination hexes.

Where in the road did I stumble upon it?

Roll a 1d(Road Length) that is where you get on the road

What does this Polite Land road end in? (1d10 twice, once for each end)

1-3	Village
4-5	Town
5-8	Natural Landmark
9	Fortified Keep
10	Ruins (either a dungeon or just signs of civilizations past)

Where direction does this Road go? (2d6)

2	It abruptly ends (It's missing in this hex, but continues on past it)
3	It exits the nearest clockwise edge from entrance
4-5	It exits the 2nd nearest clockwise edge from entrance
6-8	It exits through the Opposite Edge
9-10	It exits the 2nd nearest counterclockwise edge from entrance
11	It exits the nearest counterclockwise edge from entrance
12	It forks (roll again for branch distance and what the branch ends in)

Author's Notes: Roads are mechanically favored to continue in straight lines and shouldn't end up making loops within themselves. Personally, I really like the idea of roads having meaningful things on both sides and this way you also start with another known location and a way to reach it from the starting town.

Rivers

If a road would start in a water terrain hex and then go into a non-water terrain hex they are instead rivers and follow the same generation procedure.

3. Terrain of Nearby Hexes

Below is how to determine adjacent terrain to the hex you are in

Surrounding Terrain of the Hex Just Entered Table (1d20)

Roll	Plains	Forest	Hills	Mountains	Swamp	Water
1-9	Plains	Forest	Hills	Mountains	Swamp	Water
10-14	Forest	Plains	Mountains	Hills	Water	Swamp
15-17	Hills	Swamp	Plains	Forest	Plains	Plains
18	Mountains	Hills	Forest	Plains	Hills	Hills
19	Swamp	Mountains	Swamp	Swamp	Mountains	Mountains
20	Water	Water	Water	Water	Forest	Forest

Author's Notes: Assume water terrain hexes to mean coasts, deltas, and lagoons rather than open sea. Seas and Oceans are added by Towns and Cities with ports.

Example of how the table works:

After entering a Hex with the Plains terrain, you notice the terrain of the surrounding hexes. Going clockwise starting at the flat top of the hex you assign each surrounding hex a terrain type. Lets say you go From Hex 0,0 to Hex 0,-2 You would roll a d20 five times and what ever terrain is rolled is the terrain of that hex. Let's say we rolled the following 11,7,15,6, and 2. This means that around this hex are hills, forest, and more plains.

Normally one would roll for the terrain adjacent to the starting hex the same way just at the start of play with the only difference being they would first roll a d20 and select a type of terrain for the starting hex as if they had entered a plains hex. If several of the hexes have already be assigned terrain types then simply roll less d20's.