Before starting map modding, you need the following:

• SAD_CommonLib
  To make possible saving and loading modded maps. The mod introduces a new mod item for maps.
  https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=3115193939
  
• Test Mod Map
  This is a copy of a vanilla map, with some small edits. Not required at all, but it shows how to make a new map and a new region as example.
  https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=2995127909
  
• Start the game in debug mode
  In order to have access to the map editor and the dev tools.

The mod Project-X: Nebula is not compatible and should be removed in order to make the map modding work. It uses an obsolete map modding approach that interfere with this version.

After having the required mods enabled in the mod manager, go to the Mod editor.
Inspect the mod "Test Mod Map". It has 3 mod items: a Biome, a Map and a Region


The Biome is a thing used only for the map generation. We need it only for its Group property, which is the link between all the maps in a region.
The Region defines many common map properties, like the active seasons. The region in the test map is a copy of Sobrius, but with changed Biome Group. We need an unique region, because otherwise if the map is made for an existing one, then the unique seeds will start producing different maps. If that is the point, or an existing map should be changed, then the biome and region items are not required.
The Map defines the map itself and allows the map to be saved and loaded. Its parameters, like the size, should be the same as the ones of the other maps. The test map is a copy of an existing map as well, with some simple edits.

A real example for a modded map and region is the Nebula mod:

Create a mod and add the Map Modding as a dependency.



After having your own map mod item added to you mod, it's time to start editing the map itself. If you are already experienced in map editing, then the map creating could start form scratch. Otherwise hit F5 to open a list with all maps and double click a pre-generated map from one of the existing regions.



After loading the map, hit F3 in the game - this is the shortcut toggle to enter or exit map editing mode. Here everything is changeable, but only the modded map can be saved after being changed in the editor. In order to save the map after being loaded, an additional reload is required inside map editor mode, to ensure that the game logic isn't started. To do so hit Ctrl-F5. Now, inside the map mod item, hit the button Import Loaded Map.



This will save the map inside the mod, under the map mod item. Now hit F3 again and navigate to your map. Reload the map before start editing it via Ctrl-F5. After making the changes, hit the button Save Loaded Map inside the map mod item.

The passability of the map can be visualized via Ctrl-9.

The mod adds new mod items: "Map", "Biome" and "Prefab". The map item defines a map, which is a part of a specific region (e.g. Sobrious, Desertum, Saltu). In order to create a new region, the existing mod item Region has to be used. The link between the region and the maps is defined by the "Biome Group" property in the map mod item. Here comes the need of the biome mod item. The "biome" term does not define a new Region, but something specific for the random map generator. The only thing useful in this mod item is the group of the preset. These relations can be seen in the example mod "Test Mod Map".

Map creation workflow:

• Create a mod item map. The mod item ID is the map name. Copy an existing map from RandomMap group, if you are not familiar with the map properties.
  
• Ensure that you have started the game in DEBUG mode in Steam. Go to the mod editor map and hit F5. A list with maps will be displayed, and double clicking it should load that map.
  
• Open the map editor with F3 (it will be an EMPTY map).
  
• Reload the map using Ctrl-F5 to disable game logic.
  
• Edit the map (terrain, objects, effects, etc).
  
• Hit "Save Loaded Map" to save it.
  
• Exit the map editor by hitting F3 again and reload the map via Ctrl-F5 to test it.