Building Unreal Engine using Source Code from GitHub

The purpose of this tutorial is to provide a step-by-step guide to setting up your GitHub account, obtaining the source code for Unreal Engine, and building a version of the engine in Visual Studio. This tutorial is intended for anyone who has never gone through this process before, and who may be unfamiliar with GitHub or Visual Studio. This tutorial will be focused on Windows operating systems. There are some differences when setting up for Mac usage, but those differences are generally minor.

Initial Setup

Unreal Engine Account

Make sure you have an Unreal Engine account.

GitHub Account

Make sure you have a GitHub account.

Go to your Unreal Engine account and link your GitHub account. You will receive an email from GitHub notifying you that you have been invited to join the EpicGames Organization. Click the link in the email to join EpicGames, or visit the Organization page on GitHub and click the button to join the Organization (make sure you are logged into your GitHub account when you do this). Once you have joined the Organization, you will see the Unreal Engine repository that is maintained by the EpicGames Organization.

Install the GitHub Client

Download and install the GitHub client.

Install Visual Studio

If you do not already have Visual Studio installed, you can get it here. You can then download and use Visual Studio Community for free, which is the same as Visual Studio Professional but with a more restrictive license. Make sure to check the license terms for Community to be sure you are able to use it. I will be using the Professional version in my examples, but there should be no difference in how it works for you if you are using a different version of Visual Studio.

Visual Studio Setup

This section is optional. The following steps will allow you to closely mimic the way I have Visual Studio set up. I find this setup to be very useful, but it is entirely up to you if you want to follow these suggestions.

Start Visual Studio, then right-click on an empty area of the toolbar and make sure the Standard toolbar option is selected (has a check mark). If you are not sure what the different Visual Studio toolbars are, it may be helpful to make sure this is the only toolbar currently displayed for now. You can hide or display toolbars as you choose.

Click the down arrow at the far right side of the Standard toolbar, select “Add or Remove Buttons”, then make sure “Solution Configurations” and “Solution Platforms” are both selected.

Right-click an empty area of the toolbar and select the “Customize” option at the bottom of the context menu.

In the Customize window, click the Commands tab, then select the Toolbar radio button and find the Standard toolbar in the dropdown menu. In the Controls window, locate the Solution Configurations option, click it, then click "Modify Selection" to the right. Set the width to 200, then close the Customize window. This extends the width of the Solution Configuration option in your toolbar so that the full text will be displayed.

You can customize a large number of Visual Studio toolbar items in this way. It is entirely up to you if you choose to do so.

Get Source Code

Create Your Own Fork

Log into GitHub. Click on your profile picture, then "My Organisations". If you added your GitHub account to your Unreal Engine account, then you will see that you have been added to the EpicGames Organization in GitHub.

Click on the Epic Games logo to go to the Epic Games page on GitHub. You will be able to see the prival "UnrealEngine" repository. This is the one you want for the purposes of this tutorial. Click on that repository.

The repository screen allows you to explore all of the files in the repository, as well as a bunch of stats about the repository. Feel free to look around later. For now, click on the Fork button in the top right.

You will see a prompt asking you want to fork the repository. You should see two options, your own account or the Epic Games account. You will only be able to select your own account, so do so.

After a few seconds, you will see another repository page, but this one will be your own repository. It is identical to the current state of the repository at Epic Games, but it will not automatically update. I will let you know in another tutorial how you can update your repository with any updates that Epic Games makes to their repository.

Cloning Your Fork

Now that you have your fork of the source code, you need to clone a copy of the repository to your local computer. There are a couple ways to do this, and I will show you both. Whichever way you decide to do it is up to you. The end result is the same.

Use GitHub Client

Start the GitHub Client that you installed previously. When it loads, you will be asked to log in. Log in with your GitHub account information.

Once you are logged in, you will be presented with a blank interface with a large prompt inviting you to “Get started by adding a repository.”

Click on "Clone a repository from the internet" and select your newly created "UnrealEngine" repository from the list of available repositories.

You will be prompted for a location to save the repository. My suggestion would be to create a GitHub folder on your hard drive of choice and select that folder. Make sure you have plenty of space available, as this folder can become quite large. Click OK, and the client will begin cloning the repository to your computer. This will most likely take a few minutes.

Clone from GitHub

Open GitHub in your browser and log in. Navigate to your UnrealEngine repository by clicking on your profile icon in the top right, select "Your Repositories" and find your UE repo. Click "Code -> Open with GitHub Desktop" to open the repo in GitHub Desktop. You will then be prompted to select an location to save your files to directly.

If you are using Chrome, you will likely see a warning message appear. Other browsers may show something similar. Click “Launch Application”, or whatever option allows you to continue.

The GitHub client will begin cloning the repository to your computer. This will take a while.

When the GitHub client has finished cloning the repository, it will display a history of all of the commits to the repository.

I can hear you now: “Great, that was easy. Now how do I start the Editor?” Well, we’re not done just yet.

Get Dependencies

Build the Engine

If you have not already done so, open a Windows Explorer window and navigate to the folder where your local repository is located. Locate the GenerateProjectFiles.bat file and double-click on it to run it.

This will create a new file in your folder: UE5.sln. Double-click on it to open it in Visual Studio. When Visual Studio opens the solution, your Solution Explorer should look something like this:

Check your Solution Configuration and Solution Platform to make sure they are set to Development Editor and Win64 respectively.

Feel free to explore later, but for now right-click on the UE project in the Engine folder and select Build.

Depending on your computer, this may take a while. Now would be a good time to get a snack. Or some coffee. Or both.

Welcome back! If everything went well, you should now have a version of Unreal Engine built from source code and ready to go. If you ran into any build errors, you can search for help on the Documentation page, which also searches the Forums.

“So, can we start the Engine now?” Patience, Grasshopper. We are almost there. Go back to your Windows Explorer window where you should still be looking at your repository folder. From there navigate down to \Engine\Binaries\Win64.

Scroll all the way down to the bottom of this folder. At the bottom you will see a file named UnrealVersionSelector-Win64-Shipping.exe Double-click this file to run it. This file registers your new Unreal Engine with Windows.

Now, the moment you have been waiting for. Yes! We can start the Engine now. Near the top of this same folder, you will find a file named UE5Editor.exe Double-click on this file to start the Engine.

The initial launch may take a little while as the Editor goes through some first-run setup tasks. It will not be long before you see the Project Browser appear.

You will most likely also see a notice at the bottom of your screen about shaders compiling. This should only happen the first time the Editor is run.

You should be all set at this point. If you have any additional questions, please use the link above to the Documentation search, or visit the Forums. I will also be creating a tutorial for upgrading your GitHub repository, so stay tuned for that. Feedback is always welcome. Have fun!

Opening an existing C++ project

If this is the first time you've built the engine from the source code but you already have existing C++ projects, you'll want to be able to debug your project and step into the engine code from time to time in order to troubleshoot why your own code isn't working. Your original C++ project doesn't know about the engine or the source files, so when you try to step into an engine side method, you'll get visual studio notices saying that the program debug database (PDB) doesn't exist for those objects. This is obviously because it wasn't using the engine source code when you compiled the project, so no PDB's were generated.

Fortunately, it's pretty straight forward to bring your existing project into the engine build. All you have to do is open up the project in your newly built engine. You'll probably get a notice that the existing project is not up to date with the new engine build and it wants to convert the project. This is pretty harmless, so it's okay to convert in place. The engine will update a bunch of files in your intermediate folders and then will try to recompile the whole project. If you're using source control, you will need to make sure that you have write access to these intermediate files (you'll get errors with a list of files which can't be written to -- just check them out). Once the project has been updated, you are safe to close the editor and open up your newly updated project solution. You'll notice within the solution explorer that your existing game was put into a "Games" folder and you now have full access to the engine source code within the solution explorer. Now, there are a few things you need to pay close attention to:

1. Your build configuration has a bunch of new options. These may have changed. You want to make sure that you're still using the "Development Editor" or "Debug Editor" configurations. If you use other build configurations, you may get some funky linker errors originating within the engine.

2. You want to verify that you're still building the Win64 version of the binary. In my case, it got toggled to Win32.

When you're ready, you want to right click on your own game project and select "Debug -> Start New Instance" (alternatively, you can right click and set it as the default start up project and then press F5). Since this is the first time your project is being built with the engine, it will recompile a whole bunch of engine files which takes anywhere from 5-15 minutes, depending on your processor speed. Subsequent game builds will not require an engine rebuild. Once the build has completed, the project will launch your game application and you can debug as normal. Now however, you can step directly into the engine code to troubleshoot your engine method calls!

If you're feeling really ambitious, you can even extend the capabilities of the engine itself. By running the engine / editor in debug mode, you can also see exactly where the engine itself is crashing and fix the code. No need to wait for Epic to release an update on a monthly cycle :)

Things I don't know yet:

• What happens to your engine updates when you upgrade to a new engine version?
• How to submit your engine updates via GitHub to Epic for inclusion in the next release?