Unreal Engine - Scratchpad.md

Linux

Compile unreal from source - Linux

Compile unreal from source - Linux

Follow this documentation to compile unreal from source: https://docs.unrealengine.com/4.27/en-US/SharingAndReleasing/Linux/BeginnerLinuxDeveloper/SettingUpAnUnrealWorkflow/

---

Make clean

Make clean

make ARGS=-clean

---

Generate project files command line

Generate project files command line

To generate project files you have to execute the following command: sh ./GenerateProjectFiles.sh /path/to/workspace/PROJECT/PROJECT.uproject -game -engine -vscode

NOTE: -vscode is used to generate VSCode workspace.

NOTE: Follow this guide to properly setup VSCode: https://docs.unrealengine.com/5.0/en-US/setting-up-visual-studio-code-for-unreal-engine/

---

Unreal versioning of Binaries

Unreal versioning of Binaries

How do I change version of compiled unreal engine?

Manually-Specified Build ID

It is possible to force your Build ID to a specific value. You can accomplish this by adding a BuildId entry (as a string variable) to your Engine/Build/Build.version JSON file, but it is not recommended, as it removes the check to prevent using incompatible Modules. It is particularly easy to run outdated code if using a forced Build ID with Plugins that may be shared between multiple Projects. SOURCE: https://docs.unrealengine.com/4.27/en-US/ProductionPipelines/BuildTools/UnrealBuildTool/VersioningofBinaries/

For some reason the above doesn't work. What you have to do is:

1. Execute ./Setup.sh
2. Navigate to .config/Epic/UnrealEngine/Install.ini
3. Remove any line but the header, the file should look exactly like this:

[Installations]

1. Create a new directory and file: .config/Epic/UnrealEngine/LauncherInstalled.dat
2. Add the following data:

{
    "InstallationList": [
        {
            "AppName": "UE_5.1",
            "InstallLocation": "/path/to/UnrealEngine"
        }
    ]
}

1. Done, enjoy your engine version.

Note: The source of this info is UE discord Linux channel.

---

Windows

Best Windwows toolchain version

You can check the best toolchain version for Urneal engine here: UnrealEngine/Engine/Config/Windows /Windows_SDK.json

Good to know

Rename classes, modules without breaking Blueprint

Rename classes, modules without breaking Blueprint

After a class or module rename you have to add a Core Redirect to make sure the BPs will continue working. Follow the doc here: https://docs.unrealengine.com/4.27/en-US/ProgrammingAndScripting/ProgrammingWithCPP/Assets/CoreRedirects/

Note 1: The MatchSubstring=true doesn't work so it's needed to use the full path

+EnumRedirects=(OldName="/Script/StrayBalls.EFlTeam", NewName="/Script/MGame.EFlTeam")
+ClassRedirects=(OldName="/Script/StrayBalls.FlHolographicObjectManager", NewName="/Script/MGame.FlHolographicObjectManager")
+StructRedirects=(OldName="/Script/StrayBalls.FlMeshMaterials", NewName="/Script/MGame.FlMeshMaterials")

Note 2: Make sure to put the redirects under [CoreRedirects] inside DefaultEngine.ini

Note 3: Once the CoreRedirects works, you can re-compile and re-save all the BPs / Assets to make sure those use the new calss. Afterward you can remove the CoreRedirects.

To perform the above action you can use the UE4 commandlet

./UE4Editor /path/to/workspace/PROJECT/PROJECT.uproject -run=resavepackages
   OR
./UE4Editor /path/to/workspace/PROJECT/PROJECT.uproject -run=resavepackages -fixupredirectors

---

Event to detect when a controller is connected or disconnected

IPlatformInputDeviceMapper::GetOnInputDeviceConnectionChange()

Unreal Engine UObject pointers types

// Can be considered as a raw pointer.
TObjectPtr<UInputAction> MoveAction; 

// Store a reference of an object that may be already garbage collected (owns it)
TSoftObjectPtr<UInputAction> MoveAction; 

// Stores a non-owning reference to the object (acting like a weak smart ptr)
TWeakObjectPtr<UInputAction> MoveAction; 

// Store a reference of an object and owns it, preventing to garbage collect.
TStrongObjectPtr<UInputAction> MoveAction;