C++ mod setup¶
There's quite a bit of setup required before you can start coding your C++ mod. Thankfully, the steps are well documented and you only have to do this once, when initially setting up your environment.
Note
This page borrows extensively from the official UE4SS documentation for creating C++ mods. I've tweaked and tailored the steps specifically for Subnautica 2, but you'll still find a lot of very useful and relevant information in the official docs:
Prerequisites¶
Before starting this section, make sure you've already completed the earlier setup pages:
- UE4SS is installed and working with Subnautica 2.
- Visual Studio 2022 is installed with the relevant workloads and components.
- GitHub Desktop is installed.
- Your GitHub account is linked to your Epic Games account for Unreal Engine source access.
- Rust is installed.
- You can launch the game and see the UE4SS console.
- You have a modding workspace where you can keep your source code under Git.
The official UE4SS guide uses the main UE4SS repository in it's setup steps. For this guide, we'll use the Subnautica 2 fork instead:
Set up the UE4SS source¶
For this section, I recommend using command-line git rather than GitHub Desktop. The UE4SS source tree has recursive submodules, including the Unreal Engine source dependency, and I found that GitHub Desktop got itself in a bit of a muddle when cloning the UE4SS repository. I believe in part due to authentication requirements for the Unreal Engine submodule dependencies.
Go to the start menu, and start typing Developer PowerShell and you should see an icon for Developer PowerShell for VS. Click the icon to run PowerShell. We'll use this for the git and cmake commands in this section, as it sets up paths and the Visual Studio build environment automatically.
First, check that git and cmake are both available:
If git is not recognised, check you've properly installed GitHub Desktop. If cmake is not recognised, open the Visual Studio Installer and check that you've selected all the right workloads and components.
Now change directory to your modding workspace. In my setup, that looks like this:
Clone the Subnautica 2 UE4SS repository fork:
Before initialising the submodules, tell Git to use HTTPS for GitHub submodules. I had to do this in order to clone the sub-modules, as without it git was complaining about SSL host issues:
Now initialise the submodules:
This step can take a while. It may also open a browser window asking you to log into GitHub. That is expected if Git needs authenticated access.
Unreal Engine source access
The deps/first/Unreal submodule requires access to Epic's private Unreal Engine GitHub repository. If you have not already done this, link your GitHub account to your Epic Games account, then accept the email invitation to join the EpicGames GitHub organization.
Without that access, Git may not be able to download the Unreal Engine submodule.
If submodule setup fails
If Git fails with Host key verification failed while cloning a submodule such as patternsleuth, Git is probably trying to use SSH before your machine is set up for GitHub SSH access. Run:
git config --global url."https://github.com/".insteadOf "git@github.com:"
git submodule sync --recursive
git submodule update --init --recursive
If a failed attempt leaves a submodule in a broken state, you may see errors like No such ref: HEAD or Unable to find current revision in submodule path. Clear the failed submodule state and try again:
git submodule deinit -f deps/first/patternsleuth
git submodule deinit -f deps/first/Unreal
git submodule sync --recursive
git submodule update --init --recursive
If deinit says one of those submodules is not initialised, don't panic. Keep going with the remaining commands.