- File Location Management
- Common Folder
- Events Folder
- Gfx Folder
- History Folder
- Interface Folder
- Localisation Folder
- Map Folder
This is where a description of what most of the files mean/do. The game files are found under C:Program Files (x86)SteamsteamappscommonHearts of Iron IV, in case you wondered where most of those cool files people have in their mods come from.
/aces
This folder contains the traits that aerial aces can spawn with. You can modify existing traits, or add your own (just make sure you give it a unique tag, so it doesn't override any pre-existing traits).
/ai_focuses
Here you will find the focus priority list for AI countries (obviously, only for the nations that have unique focus trees). You can also change the way AI behaves in different situations here (eg. you can tell German AI to focus on building anti-air defenses when they are defending, or tell French AI to build more tanks when they are on the offensive).
/ai_peace
These files define what the AI will do when in a peace conference. If you want communist AI to go for world domination, and always annex everything, look no further.
/ai_strategy
These files tell the AI which type of divisions it should prioritize under what conditions. Like that they should not train cavalry divisions after they research trucks. Or just not train them at all. Ever.
/ai_templates
Not entirely sure about these. They probably tell the AI in a convoluted way when to upgrade their templates, and what to upgrade them with.
/autonomous_states
Each file in here is a different subject type. You can modify what abilities each type has, or how much the subject will want to increase its autonomy, or how much the overlord will want to decrease it.
/bookmarks
Basically where the setup for singleplayer games is. When the game prompts you with the screen of the major nations, and lists USA, Japan, UK, Germany, etc, a chunk of that data is stored here. The actual changing of data, i.e. changing the ideas, ideology, and "TAG_SCENARIO_NAME_DESC" are changeable in the Localisation Folder under the bookmarks category, to the respective scenario.
/buildings
Ever wanted to make Military Factories (labeled as "arms_factory") cost 1 to produce? Ever wanted Civilian Factories (labeled as "industrial_complex") to be very easy to convert to Mil. Fac's? This is where you do it, along with all build-able objects that get placed in provinces/states.
/continuous_focus
Know those continuous focuses you rarely ever use, because the one for air production is the best? Here you can modify them to give them proper bonuses! Or you can add your own overpowered continuous focuses if you so desire.
/countries
This is where the "graphical_culture" comes from, as well as the color. Deleting this file will lead to John Lennon appearing.
/country_leader
Want to make Hitler a real swell guy? The trait list is here! Make FDR have the Spirit of Genghis, or add new traits to use!
/country_tags
This is where the TAG relates to the graphical_culture and color back in the /Countries folder.
/defines
00_defines.lua is what is important here, as it "defines" what the start date is, or the "minimum" date that is possible. It also includes a TON of other stuff, so this folder is known as the "defines" folder.
/difficulty_settings
Here you can add to the list of nations that can have custom difficulty settings at the start of each game. If you don't want Poland to be folded in half by the German army, you can add an entry for Poland here, and just boost their slider before starting the game. All done. Poland is now overpowered. You're welcome.
/idea_tags
This is where the "slots" exist for economy laws, political advisers, military staff.
/ideas
This is where you can actually tinker with or add/remove ideas for nations, as well as add different or new political advisers for each nation. Say you want Switzerland not to have a naval invasion high command guy. You can remove him!
/ideologies
This is where the rulesets exist for ideologies. Want communist nations to guarantee other ideologies? You can do that!
/names
Here you can find the pool of names for each nation, that the game draws from, when it needs to name a randomly generated character (like a general, a country leader, or a flying ace).
/national_focus
Essentially where all of the national focus trees are hidden. Want France to be ludicrously OP? Want China to have a focus to give them the spirit of genghis? You can do that here.
/on_actions
These handy little files enable your code to be executed when certain things happen. Want an event to fire when the game starts? The on_actions.txt has got you covered! Want to randomly fire one of several events when elections start in your country? Well... that's basically already how elections work, but you get the point. With these files you can make things happen automatically, when other things happen.
/opinion_modifiers
Here you can find all the reasons people can hate Hitler. These are the opinion modifiers, that can be applied with the add_opinion_modifier = { ... } command.
/portraits
These are just the rules the game uses, when it needs to choose a portrait for randomly generated leaders and generals. If you've added default female portraits to the game, this is where you can tell the game to use them when generating female leaders (does that ever happen? I don't think that ever happens).
/resources
The strategic resources of the game are listed here. You'll probably only need this folder, if you're adding resources to the game.
/scripted_effects
This folder contains the closest things you can have to traditional "functions" in HOI4 modding terms. You can define a set of commands, give it a name, and later call it with a single line of code. For example, you could write a scripted effect for inviting a nation to Germany's faction, giving them a technology boost, and an opinion modifier with Germany (let's call this effect "become_buddies_with_GER". Every time you want to apply this effect to a country, instead of having to type out all three commands, you can simply just write "become_buddies_with_GER = yes", and the whole thing is done.
/scripted_localisation
Here you can define your own dynamic localisation keys. Not entirely sure what the use case is, but there is a fairly understandable sample with explanation inside.
/scripted_triggers
Similar to scripted_effects, only this time with triggers. You can define a set of triggers, and give it a name. Every time you need to check those triggers, you can simply invoke the name of your scripted trigger, and all conditions will be checked.
/state_category
Files in here are pretty simple. They define how many building slots each state category can hold, and what their color is on the state mapmode.
/technologies
Shows all the techs, their position in the subfolders, the research cost, the beginning research year, what techs they lead to with what coefficients, and what they reference to.
/technology_sharing
Technology sharing groups come here. You can define the conditions for joining one (though I guess these only applies to joining via the continuous focus), and what the bonuses are.
/technology_tags
You can find the names of each technology category here. Useful if you want to create a research bonus as a reward for an event/focus, and need the name of the proper category.
/terrain
Attributes of different terrain types can be found here. If you want to create a world where it takes mere hours for a ship to cross an ocean, or deserts are like impregnable fortresses, this is the folder you need to mess around in.
/timed_activities
Supposedly, Paradox wanted to create more timed activities. As is, only the "stage coup" action is here, and the fact that it needs 1000 infantry equipment. Not sure what to make of this information.
/unit_leader
These files contain the bonuses for each skill level, and trait of generals and admirals. They work in a similar fashion to the normal leader traits, but with combat bonuses, so don't try to add a bonus to political power gain here.
/unit_tags
Different unit categories. These are mostly used in technologies (eg. when a technology gives a bonus to all infantry types, it refers to "category_all_infantry").
/units
This is a big folder. It has the in-game manpower, training, org, etc values. In the /Names subfolder, it shows the names for the boats that get produced. The /Equipment subfolder shows the actual battle values and such for each item, such as the armor for tanks, the production cost for planes, and the resources used. Inside the /Equipment folder is the /Upgrades subfolder, which shows what equipment can have "variants" and the max levels for those variants, and where the XP cost is located.
/wargoals
Wargoal types are in this folder, but the name probably gave that away. The file in there defines the time it takes to generate each type, the bonuses they give at the peace conference, the time after which they expire, the threat they generate, and other such things.
As the name suggests, this folder contains all the events that can fire in the game. Getting started with event modding can seem overwhelming, but you can learn a lot just by looking at existing events, and experimenting. Also, there is an entire page worth of stuff on event modding on the HOI4 wiki.
This folder is a beast. It contains pretty much all of the graphical elements that show up in the game. Portraits, focus pictures, flags, unit models, interface buttons, you name it. If you're looking for a picture to use for your custom focus, or national spirit, you can pick and choose to your liking in the /interface/goals and the /interface/ideas folder. Same goes for event pictures, only those are not in the interface subfolder, but - surprisingly - in the event_pictures folder. If you want to add new graphical elements (eg. a new portrait), this is the folder you'll need to place it in BUT you'll also need to reference it in an interface file (more on those in the Interface folder section).
/countries
Sets "oob" which references the /history/units folder. Sets what techs a country starts with, sets the politics, and leaders with their traits. REMEMBER: in the Leader list, the LOWEST leader of the ruling ideology is put into power. This folder is also where the "last_election", "elections_allowed" and "election_frequency" are housed, along with whether elections are even allowed ("elections_allowed").
/states
This is a list of every state in the game. All 742 of them. Each state controls some provinces, has a controller, core, and claim ability in it. This is also where the starting amount of Civ Facs and Mil Facs, along with bunkers, infrastructure, etc, are. If you need help finding out what states belong to who, use this.
/units
In this folder, you can find OOBs (Order of Battle) for different nations. OOBs define what kind of army templates, factory setups, air wings and divisions each country has at the start, and where those divisions are on the map. Usually, there is one for the 1936 start date and one for the 1939 date, but there are also some that can be added via events or focuses. If you want to make a focus that trains an elite overpowered division to your favorite country, you'll need to create a file for it here.
Similar to the localisation folder, the Interface folder has everything plopped out in the open, with no subfolders. The reason this folder exists is for gui purposes, or Graphical User Interface. So, for example, "countrytechtreeview.gui" is where the year numbers on the armor tree can be found, off to the left. "countrytechtreeview.gui" also does other things, relating to the "country tech tree view". The Interface folder has a whole lot off stuff that I know nothing about, as well, so its best to a.) poke around for what seems relevant to the item you want to change, and b.) after giving up hope, come to the subreddit and say u/insanegorey is a bad man and ask our community for assistance. Along with the .gui files, you'll find some .gfx files in here. Those are a bit simpler, as they simply assign a key to a sprite. For example, if you have the following national spirit picture: gfxinterfacenational_spiritespirit_the_corps.dds , you'll want to have a SpriteType entry in one of your .gfx files in the interface folder, that assigns this path to a name like "GFX_idea_espirit_de_corps". From then on, you can assign it to a national spirit by adding the following line to it:
picture = espirit_de_corpsSince the Localisation folder has no subfolder, this will require fewer special characters on my part. The reason of being for the Localisation folder is to house a LOT of text. This is done so that when making focus trees, events, etc, you do not need to write in what the tooltip/definition of the item you are making, word for word. You can reference in the event you are building, for example, to a line of text found in the events text file, in localisation.
If you look under the bookmarks category of text files, (shouldn't be too far down) you can, under the English version if you speak English, see the text that the scenario picker takes from. You can make a mod, for example, using these localisation files that listed every tooltip with the word "memes", if you had the time to edit all of the text files, and change all the text to the word.
This is the folder you'll need, if you want to change the map (surprised?). Some things that are map-related can be done via the in-game nudge tool, but for absolute control over the map, you'll want to get to know this folder better.
adjacencies.csv: Defines sea straits (that are crossable with armies), and impassable borders (like the Himalayas)
adjacency_rules.txt: Defines the crossing rules for canals and some special straits. For example, it specifies who can cross, if you hold the Suez canal (friends, hostiles, neutrals etc.)
airports.txt, buildings.txt, rocketsites.txt, unitstacks.txt, weatherpositions.txt: These all serve similar purposes. They tell the game where to place things on the map. In buildings.txt, there is an entry for each possible building that can have a visible model on the map, and the entry tells which state it belongs to, and where exactly it is (in 3D coordinates). In the unitstacks.txt the same is done for unit models. It's a tedious task to modify these by hand, so you're better off using the nudge tool whenever you can.
definitions.csv: A list of all provinces in the game. First column is the province ID, 2nd 3rd and 4th columns are an RGB code, that has to match the province's RGB code in the provinces.bmp (note that each province needs to have a unique RGB color). The 5th column defines whether the province is a land or sea province, the 6th column is whether the province is coastal or not (sea provinces count as coastal), while the 7th is the terrain type (like forest, urban, desert etc.). The 8th column is the ID of the continent that the province is a part of. 1 is Europe, 2 is North America, 3 is South America, 4 is Australia, 5 is Africa, 6 is Asia, 7 is Middle East and 0 is neither (oceans).
heightmap.bmp: A heightmap of the game world. This is only for visual representation, so if you only want to change the terrain type of a province, this is not the file you need. From what I can tell, this file doesn't influence how "bumpy" the terrain looks, it only paints individual places according to their height.
provinces.bmp: A map of all the provinces in the game. If you're adding a new province, make sure it has a unique color on this map. If you're only modifying the borders of existing provinces, you needn't worry about creating new adjacencies, or removing existing ones. These things are handled automatically by the game, so if you isolate two provinces that were previously connected, the game will recognize that troops can no longer cross between them (pretty cool, huh?). However, if you change the shape, or the location of a province significantly, you should probably edit the unit model positions on that province afterwards. This can be easily done by using the nudge tool.
rivers.bmp: A map of all the rivers in the game. The color of the river determines the in-game width of the visual representation (the darker the color, the wider it will look) I'm not sure whether river crossing penalties for divisions are automatically added if you add a new river here, but if you do everything right, you can get a river to show up in the game, just by drawing one in here. If your new river flows into a different river, make sure you add a single red pixel where the connection is (look at other rivers for examples).
terrain.bmp: This map exists, so that the player can look at a province, and tell at a glance what kind of terrain it might be. Each color represents a different terrain type, and the shapes on the map follow the province shapes. For example, a yellow blob on this map represents a large city, and shows up as such in the game. Note, that the actual terrain type is not determined by this file, this is just a visual aid for the player. To change terrain type, you have to modify the definitions.csv file (though it is recommended to modify this map too, so that the player doesn't get confused when he encounters a mountain type province in the middle of the Siberian plains).
trees.bmp: The name kind of gives it away. This is a map of all the trees that appear on the map. Different colors are for different types of trees (you wouldn't want tropical trees in Canada, right?).
world_normal.bmp: Similar to the heightmap, but this one is probably responsible for the 3D height and depth of the map.
