Modding

Basics

Mod-making tutorials

Mod-making tutorials are available at the Modding Tutorials page. If you can't find what you need, you should try looking in Random Bits of Information to check if the information you're looking for has been found but just hasn't been organized into the correct article yet.

Mod-making Templates

Mod Development Cookiecutter (automatically build your mod development environment)

What you can mod

You can mod defs, code, images, and sounds.

Defs: XML files containing lists of definitions for use by the game. There are a lot of these. They define every thing, skills, storyteller, and many other types of data. Find them in YourModName/Defs. More about this later.
Code: You can add .NET assemblies and the game will load them. Place your DLLs in YourModName/Assemblies. More about this later.
Images: You can add images.
Sounds: You can add sound files.
Jobs: A useful link here https://github.com/Mehni/ExampleJob/wiki - covers JobGivers WorkGivers and Toils
- Higher level, explanation on how pawns think: https://github.com/roxxploxx/RimWorldModGuide/wiki/SHORTTUTORIAL%3A-How-Pawns-Think

The basics: Defs

The most basic kind of RimWorld modding is done by editing defs.

Definitions each define some piece of the game. Different kinds of definitions can define:

Sound
Weapons
Buildings
Plants
Animals
More (To be determined)

When the game runs, it collects all the definitions into pools. It then semi-randomly draws from these pools in various circumstances. It will randomly draw guns of a certain category to arm a new enemy mercenary. Or, it will randomly spawn an animal type on the edge of the map. Modding the game means adding your definitions to these pools and watching the game use them in this way.

Definitions are organized into packages. Each package is saved as a single XML file.

Groups of packages are organized into mods. A mod is a unit of interlinked functionality and content. It could be a pack of new weapons, a new animal, or a total conversion of the game. A mod will usually contain several packages of various types, as well as content like images and sounds.

The base game is defined in a single mod called Core.

Players can choose which mods to activate. In some cases, several mods can be active at once. You could use a medieval mod to replace the core mod, and add on a weapons pack created by someone else. The game will run with the medieval mod content, and also randomly spawn in weapons from the extra weapons pack.

Mod file structure

For defining new game content, XML files are used. Here is an example of the format, that applies to most of the definitions:

<?xml version="1.0" encoding="utf-8" ?>
<SomeDefs>
   <SomeDef>
      <defName>MyNewDefinitionOfContent</defName>
      <!-- more tags will appear depending on what are you defining -->
   </SomeDef>
</SomeDefs>

Remember, that the word Some must be replaced by the name of whatever are you defining. For thing it's <ThingDef>.

The RimWorld mods use the following directory structure:

┌About 
├─About.xml (Contains info about the mod)
├─Preview.png (Image that appears above the mod info in game. Max width 600px.)
│
├Assemblies (If your mod uses any DLL files put them here)
├─MyMod.dll
│
├Defs (Contains xml definitions of the mod)
├┬ThingDefs
│├─Things.xml
│└─Buildings.xml
│
├┬ResearchProjectDefs
│└─MyProjects.xml
│
│the folder name must be specific here. Look in Core mod to see what are other names supposed to be
│
├Sounds
│
├Source
├─MyMod.cs (Optionally, put the source code of your mod here)
│
├Patches
├─Patch.xml
│
├Languages
├┬English (Replace with the language name)
│├┬Keyed
││└─Keys.xml
│├┬Strings
││└┬Names
││  └─PawnNames.xml
│├┬DefInjected
││└┬ThingDef
││  └─Thing.xml
│├─LanguageInfo.xml
│└─LangIcon.png
│
├Textures (Put any image textures here, preferably in .png format.)
├┬Things
│├─MyMod_ImageA.png
│└─MyMod_ImageB.png

Mod info

This is found in MODNAME/About

The contents of About.xml are plain text. HTML Markup tags cause NullRef's.
You can have an image for your mod. Restrict the image width to 600 pixels

Textures

These are found in MODNAME/Textures

You can have any path you want from this point on.
When referencing textures in your mod, using <graphicPath>, have the complete path relative to your mod, including the filename (but not the file extension). Example for the RoyalBed Testmod: <graphicPath>Things/Building/RoyalBed</graphicPath>

For textures that have multiple faces, like animals and furniture which can be rotated; You can use the Graphic_multi class. Immediately following your <graphicPath></graphicPath>. Your Path should point to the folder containing the different textures: Texturename_side, Texturename_front, and Texturename_back.

<graphicPath>Things/Buildings/RoyalCouch/RoyalCouch</graphicPath>
<graphicClass>Graphic_multi</graphicClass>

Inside your folder:

┌Textures
└┬Things
 └┬Buildings
  └┬RoyalCouch
   ├╴RoyalCouch_side
   ├╴RoyalCouch_front
   └╴RoyalCouch_back

For plant textures that have multiple growth stages and/or utilize the Graphic_Random class, the different images for each stage must be in separate folders. These images within must also share the same filenames. For example, the corn plant has one immature form, and two different mature forms that appear at random once the plant is fully grown. Similarly to Graphic_Multi, when using the Graphic_Random class, you will always want to reference the folder containing the images rather than the images themselves. An example of how this could work:

<graphicPath>Things/Plants/CornPlant</graphicPath>
<graphicClass>Graphic_Random</graphicClass>

Your folder structure:

┌Textures
└┬Things
 └┬Plants
  └┬CornPlant
   ├╴CornPlant_A
   └╴CornPlant_B
  └┬CornPlant_Immature
   ├╴CornPlant_A
   └╴CornPlant_B

Even though there is only one image used for the immature corn plant, we must have two copies of it with the same filenames as the mature plant images in order to prevent broken textures in-game. If you wanted to add a leafless variant to a plant (such as the leafless trees in winter), another folder would be added.

┌Textures
└┬Things
 └┬Plants
  └┬CornPlant
   ├╴CornPlant_A
   └╴CornPlant_B
  └┬CornPlant_Immature
   ├╴CornPlant_A
   └╴CornPlant_B
  └┬CornPlant_Leafless
   ├╴CornPlant_A
   └╴CornPlant_B

Interactive "things"

A thing is anything that exists in the game world. It includes resources, races (humanoid and animal), buildings, furniture, and many others.

These are defined in MODNAME/Defs/ThingDefs If you make a new workbench, you'll need to define a recipe for it. This is a list, so you can have many new recipes listed.

The recipes themselves are defined in: MODNAME/Defs/RecipeDefs In here you can define what ingredients/resources are required, what can be used, and what the default recipe is.

Any new resources will need to be defined in: MODNAME/Defs/ThingDefs

Turrets

These are defined in two files in: MODNAME/Defs/ThingDefs/Buildings_Big.xml and Weapons_Guns.xml (Remember, these can be named anything)

Buildings_Big.xml defines the structure of the turret itself. For example:

<building>
	<turretGunDef>Gun_TurretImprovised</turretGunDef>
	<burstCooldownTicks>300</burstCooldownTicks>
</building>

Weapons_Gun.xml defines the weapon the turret uses. Anything can be used as a weapon for turrets, including grenades.

Resources

These are defined in: MODNAME/Defs/ThingDefs/Resources.xml

Research projects

These are found in: MODNAME/Defs/ResearchProjectDefs

You can have research trees as well, where additional research projects get unlocked as you move through. This is how to add prerequisites:

<prerequisites>
	<li>-this is the <defName> of the prerequisite-</li>
</prerequisites>

Because it's a list, you can have multiple prerequisites for a research project.

Advice

The tilde key (` or ~) brings up the development console, which will report any errors or warnings it encounters when a mod loads or during gameplay. This is the quickest way to see what, if any, errors exist in your mod. (You don't need to turn on development mode for this.)
Use development mode (found in the options menu) to help debug your mod, spawn items related to your mod, or fire incidents at will. (Or just mess around, if you'd like.)

I want my mod to...:

Or, how do I make my mod do this?

You can find links to tutorials on the Modding Tutorials page. There's also more tutorials about the basics there, so don't miss out on that.

Save/Load information. See a very useful guide at this page
Add a new value to a def
- See Custom Comp Classes
- Also might be helpful: Mod Extensions

References

Notes

You can have as many mods as you like, however too many mods may affect performance.
If the game crashes due to a mod-related reason on startup, or mods conflict with each other, then the game will reset the mods.
Mods for previous versions may be usable, however most of the time they are not compatible.