Basic Modding 

In this section you will learn how to create your first mod. We will start by simply reducing the byte cost of the Floodlight.

How Making a Mod Works 

Using UAssetGUI is a fairly simple way to create a mod. The process, which is covered in detail below, involves making a copy of Astroneer’s file structure (while only containing the necessary files) inside your mod folder. Then, UAssetGUI is used to modify those game files to your liking. Once the metadata file is set up correctly, the mod folder is packaged using unreal_pak_cli, and your mod is ready to use.

While the ways in which the game files are modified will vary, most other methods of creating mods involve a similar process as this one.

Setting up Folders 

First start by creating a new folder called TutorialMod in your AstroneerModding folder. We will be using that folder in this and future tutorials.

Next create another folder inside the TutorialMod folder called 000-TutorialMod-0.1.0_P. This name matches what the mod .pak file will later be called. You can read more on the specifications for mod .pak files in the .pak Mod File Names section of the documentation.

Creating metadata.json File 

Each mod must have a metadata.json file at the root. This file contains information about the mod. In your 000-TutorialMod-0.1.0_P folder create a file called metadata.json. Then paste the following JSON into the file. Make sure to replace YOUR_NAME with your name.

{
    "schema_version": 2,
    "name": "Tutorial Mod",
    "mod_id": "TutorialMod",
    "author": "YOUR_NAME",
    "description": "A tutorial mod.",
    "version": "0.1.0",
    "sync": "serverclient"
}

Finding the Asset to modify 

Because we are modifying an item that is already in the game we need to find the asset of the item. We want to change the byte cost of the floodlight so we need to find the ItemType asset of the floodlight. Sometimes finding the proper file can hard, but Windows search can help.

The asset file we are looking for is located at GameFiles\Astro-WindowsNoEditor\Astro\Content\Items\ItemTypes\FloodLight_IT.uasset and GameFiles\Astro-WindowsNoEditor\Astro\Content\Items\ItemTypes\FloodLight_IT.uexp. It is important to remember that each asset is split into two files and you always need to keep both together. Now we are going to copy the two files over to our folder so that we can modify them. Copy them to TutorialMod\000-TutorialMod-0.1.0_P\Astro\Content\Items\ItemTypes\FloodLight_IT.uasset and TutorialMod\000-TutorialMod-0.1.0_P\Astro\Content\Items\ItemTypes\FloodLight_IT.uexp. You will have to create the folders if they do not exist yet. It is very import that the files have the exact same folder structure as the game.

Never directly modify the files in your GameFiles folder. Should you wish to create a different mod utilizing those same files, you will have to recreate the entire GameFiles folder if you accidentially save over the original files.

Modifying the Asset 

Now open the FloodLight_IT.uasset file in the TutorialMod folder using UAssetGUI.

Each asset is made from multiple sections. The most interesting ones are usually Name Map, Import Data and most importantly the Export Data section. Assets can have a few to hundreds of exports. Exports are roughly labeled with what they contain. Finding the correct export for what you are looking for requires some practice. For small assets like this one, you can go to View > Expand All to see all the subproperties of the asset.

Here you will quickly spot the ItemCatalogData export. This is the export that contains information like unlock cost and other stuff relevant for the catalog. If you are unable to find what you are looking for, you also can search for specific text in UAssetGUI by pressing ctrl+f and typing your text into the search bar.

Each export has multiple subproperties arranged in a tree structure. You can see the subproperties by expanding the export. Click on ItemCatalogData(7) to see the contents of the catalog data. This export has a very simple structure.

At the very top of the table view there is an UnlockCost property with a number to the right. Simply the change the number to what amount of bytes you would like the floodlight to cost. For example, 500.

Then simply press Ctrl+S to save the file, or click on File > Save. You should see two .bak files appear. Ignore these files, they are simply backup files and are ignored by the software.

Packing the Mod 

Close UAssetGUI and go back to your TutorialMod folder. Right click on the 000-TutorialMod-0.1.0_P folder, then select Send to > Repack folder with unreal_pak_cli. This will create a 000-TutorialMod-0.1.0_P.pak file in the same folder.

Installing the Mod 

Double-check that the .pak file in the TutorialMod folder is named correctly. If not, rename it to 000-TutorialMod-0.1.0_P.pak. Once you have verified that the name is correct, simply drag the newly created 000-TutorialMod-0.1.0_P.pak file onto the Modloader window and you should see Tutorial Mod appear in the mod list. Make sure it is enabled in the modloader window.

Verifying the mod works 

If the mod loads into the modloader without issues, start your game. If the modloader has issues loading the mod, double check that you followed the tutorial exactly. Then head to the catalog and check that the floodlight is now costs 500 bytes. If your mod has other issues that you need additional help with, joining the Astroneer Modding Discord is your best bet.