UnrealEngine 5.5. Install and error

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(English Below)

Salut @12qs1.

Si tu veux utiliser Unreal Engine sur NixOS, je te recommande de passer par ton environnement de projet. J’ai fait un FHS pour builder un projet et lancer Unreal dedans.
Note que tu auras toujours quelques problèmes avec Unreal, notamment pas de Hot Reload et quelques bugs de contrôles (pas possible de taper une recherche dans les blueprints)

J’ai détaillé la méthode ici : UE5 (Unreal Engine 5 Game Engine) · Issue #124963 · NixOS/nixpkgs · GitHub

Il faut :

  • Installer VSCode/VSCodium et direnv
  • Ajouter le fichier shell.nix suivant au projet :
{ pkgs ? import <nixpkgs> {} }: let
  stdenv = pkgs.llvmPackages_18.stdenv;
  dotnetPkg = (with pkgs.dotnetCorePackages; combinePackages [
      sdk_9_0
    ]);
  deps = (with pkgs; [
    zlib
    zlib.dev
    openssl
    dotnetPkg
  ]);
in
(pkgs.buildFHSEnv {
  name = "UnrealEditor";

  targetPkgs = pkgs: (with pkgs;
  [ udev
    alsa-lib
    mono
    dotnet-sdk
    stdenv
    clang_18
    icu
    openssl
    zlib
    SDL2
    SDL2.dev
    SDL2 SDL2_image SDL2_ttf SDL2_mixer
    vulkan-loader
    vulkan-tools
    vulkan-validation-layers
    glib
    libxkbcommon
    nss
    nspr
    atk
    mesa
    dbus
    pango
    cairo
    libpulseaudio
    libGL
    expat
    libdrm
    wayland
  ]) ++ (with pkgs.xorg;
  [ 
    libICE
    libSM
    libX11
    libxcb
    libXcomposite
    libXcursor
    libXdamage
    libXext
    libXfixes
    libXi
    libXrandr
    libXrender
    libXScrnSaver
    libxshmfence
    libXtst
  ]);

  # runScript = "zsh";

  NIX_LD_LIBRARY_PATH = pkgs.lib.makeLibraryPath ([
    stdenv
  ] ++ deps);
  NIX_LD = "${stdenv.cc.libc_bin}/bin/ld.so";
  nativeBuildInputs = [ 
  ] ++ deps;

  shellHook = ''
    DOTNET_ROOT="${dotnetPkg}";
    DOTNET_SYSTEM_GLOBALIZATION_INVARIANT=1;
  '';
}).env
  • Ajouter le fichier .envrc suivant au projet :
use nix

# marche aussi avec flakes si tu sais faire
  • Activer direnv (direnv allow & direnv reload)
  • Générer un projet à partir du terminal
dotnet <PathToEngine>/Engine/Binaries/DotNET/UnrealBuildTool/UnrealBuildTool.dll -ProjectFiles "<PathToProject>/<YourProject>.uproject" -VSCode
  • Build le projet en mode Editor
make <YourProject>Editor

# si pas de Makefile, cette commande devrait faire la même chose
"<PathToEngine>/Engine/Build/BatchFiles/RunUBT.sh" <YourProject>Editor Linux Development  -Project="<PathToProject>/<YourProject>.uproject"
  • Lancer Unreal Engine à partir du terminal
<PathToEngine>/Engine/Binaries/Linux/UnrealEditor -Project="<PathToProject>/<YourProject>.uproject"

English translation:

If you want to use Unreal Engine in NixOS, I recommend using a project build environment. I made one to build a project and run Unreal with it.
Please note you’ll still have inconveniences with Unreal, like the lack of Hot Reload et some input issues (not possible to search terms in blueprints)

I explained how here : UE5 (Unreal Engine 5 Game Engine) · Issue #124963 · NixOS/nixpkgs · GitHub

You will need to :

  • install VSCode/VSCodium and direnv
  • Add this shell.nix file to your project :
{ pkgs ? import <nixpkgs> {} }: let
  stdenv = pkgs.llvmPackages_18.stdenv;
  dotnetPkg = (with pkgs.dotnetCorePackages; combinePackages [
      sdk_9_0
    ]);
  deps = (with pkgs; [
    zlib
    zlib.dev
    openssl
    dotnetPkg
  ]);
in
(pkgs.buildFHSEnv {
  name = "UnrealEditor";

  targetPkgs = pkgs: (with pkgs;
  [ udev
    alsa-lib
    mono
    dotnet-sdk
    stdenv
    clang_18
    icu
    openssl
    zlib
    SDL2
    SDL2.dev
    SDL2 SDL2_image SDL2_ttf SDL2_mixer
    vulkan-loader
    vulkan-tools
    vulkan-validation-layers
    glib
    libxkbcommon
    nss
    nspr
    atk
    mesa
    dbus
    pango
    cairo
    libpulseaudio
    libGL
    expat
    libdrm
    wayland
  ]) ++ (with pkgs.xorg;
  [ 
    libICE
    libSM
    libX11
    libxcb
    libXcomposite
    libXcursor
    libXdamage
    libXext
    libXfixes
    libXi
    libXrandr
    libXrender
    libXScrnSaver
    libxshmfence
    libXtst
  ]);

  # runScript = "zsh";

  NIX_LD_LIBRARY_PATH = pkgs.lib.makeLibraryPath ([
    stdenv
  ] ++ deps);
  NIX_LD = "${stdenv.cc.libc_bin}/bin/ld.so";
  nativeBuildInputs = [ 
  ] ++ deps;

  shellHook = ''
    DOTNET_ROOT="${dotnetPkg}";
    DOTNET_SYSTEM_GLOBALIZATION_INVARIANT=1;
  '';
}).env
  • Add this .envrc file to your project:
use nix

# also works with flakes if you know how to make one
  • Activate direnv (direnv allow & direnv reload)
  • Generate your project from terminal
dotnet <PathToEngine>/Engine/Binaries/DotNET/UnrealBuildTool/UnrealBuildTool.dll -ProjectFiles "<PathToProject>/<YourProject>.uproject" -VSCode
  • Build the project in Editor mode
make <YourProject>Editor

# this should run a similar command, if you don't have it
"<PathToEngine>/Engine/Build/BatchFiles/RunUBT.sh" <YourProject>Editor Linux Development  -Project="<PathToProject>/<YourProject>.uproject"
  • Run Unreal Engine from terminal
<PathToEngine>/Engine/Binaries/Linux/UnrealEditor -Project="<PathToProject>/<YourProject>.uproject"
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