F.A.Q.

Some of the most common issues regarding CARLA installation and builds are listed hereunder. Some more can be found in the GitHub issues for the project. In case any doubt is not listed here, take a look at the forum and feel free to post it.

CARLA forum

System requirements

Expected disk space to build CARLA.

It is advised to have at least 30/50GB. Building CARLA requires about 25GB of disk space, plus Unreal Engine, which is quite a similar size.

Unreal Engine on Linux requires much more disk space as it keeps all the intermediate files. This thread discusses the matter.

Recommended hardware to run CARLA.

CARLA is a very performance demanding software. At the very minimum it needs for a 4GB GPU or, even better, a dedicated GPU capable of running Unreal Engine.

Take a look at Unreal Engine's recommended hardware.

Linux build

"CarlaUE4.sh" script does not appear when downloading from GitHub.

There is no CarlaUE4.sh script in the source version of CARLA. Follow the build instructions to build CARLA from source.

To run CARLA using CarlaUE4.sh, follow the quick start installation.

"make launch" is not working on Linux.

Many different issues can be dragged during the build installation, and show like this. Here is a list of the most likely reasons why.

  • Run Unreal Engine 4.24. Something may have failed when building Unreal Engine. Try running UE editor on its own and check out that it is the 4.24 release.
  • Download the assets. The server will not be able to run without the visual content. This step is mandatory.
  • UE4_ROOT is not defined. The environment variable is not set. Remember to make it persistent session-wide by adding it to the ~/.bashrc or ~/.profile. Otherwise it will need to be set for every new shell. Run export UE4_ROOT=~/UnrealEngine_4.24 to set the variable this time.
  • Check dependencies. Make sure that everything was installed properly. Maybe one of the commands was skipped, unsuccessful or the dependencies were not suitable for the system.
  • Delete CARLA and clone it again. Just in case something went wrong. Delete CARLA and clone or download it again.
  • Meet system requirements. Ubuntu version should be 16.04 or later. CARLA needs around 15GB of disk space and a dedicated GPU (or at least one with 4GB) to run.

Other specific reasons for a system to show conflicts with CARLA may occur. Please, post these on the forum so the team can get to know more about them.

Windows build

"CarlaUE4.exe" does not appear when downloading from GitHub.

There is no CarlaUE4.exe executable in the source version of CARLA. Follow the build instructions to build CARLA from source. To directly get the CarlaUE4.exe, follow the quick start instructions.

CarlaUE4 could not be compiled. Try rebuilding it from source manually.

Something went wrong when trying to build CARLA. Rebuild using Visual Studio to discover what happened.

1. Go to carla/Unreal/CarlaUE4 and right-click the CarlaUE4.uproject.
2. Click on Generate Visual Studio project files.
3. Open the file generated with Visual Studio 2017.
4. Compile the project with Visual Studio. The shortcut is F7. The build will fail, but the issues found will be shown below.

CMake error shows but CMake is properly installed.

This issue occurs when trying to use the make command either to build the server or the client. Even if CMake is installed, updated, and added to the environment path. There may be a conflict between Visual Studio versions.

Leave only VS2017 and completely erase the rest.

Error C2440, C2672: compiler version.

The build is not using the 2017 compiler due to conflicts with other Visual Studio or Microsoft Compiler versions. Uninstall these and rebuild again.

Visual Studio is not good at getting rid of itself. To completely clean Visual Studio from the computer go to Program Files (x86)\Microsoft Visual Studio\Installer\resources\app\layout and run .\InstallCleanup.exe -full. This may need admin permissions.

To keep other Visual Studio versions, edit %appdata%\Unreal Engine\UnrealBuildTool\BuildConfiguration.xml by adding the following lines. 

<VCProjectFileGenerator>
    <Version>VisualStudio2017</Version>
</VCProjectFileGenerator>

<WindowsPlatform>
    <Compiler>VisualStudio2017</Compiler>
</WindowsPlatform>

"make launch" is not working on Windows.

Many different issues can be dragged during the build installation, and show like this. Here is a list of the most likely reasons why.

  • Restart the computer. There are many going on in the Windows build. Restart and make sure that everything is updated properly.
  • Run Unreal Engine 4.24. Something may have failed when building Unreal Engine. Run the Editor and check that 4.24 is being used.
  • Download the assets. The server will not be able to run without the visual content. This step is mandatory.
  • Visual Studio 2017. If there are other versions of Visual Studio installed or recently uninstalled, conflicts may arise. To completely clean Visual Studio from the computer go to Program Files (x86)\Microsoft Visual Studio\Installer\resources\app\layout and run .\InstallCleanup.exe -full.
  • Delete CARLA and clone it again. Just in case something went wrong. Delete CARLA and clone or download it again.
  • Meet system requirements. CARLA needs around 30/50GB of disk space and a dedicated GPU (or at least one with 4GB) to run.

Other specific reasons for a system to show conflicts with CARLA may occur. Please, post these on the forum so the team can get to know more about them.

Make is missing libintl3.dll or/and libiconv2.dll.

Download the dependencies and extract the bin content into the make installation path.

Modules are missing or built with a different engine version.

Click on Accept to rebuild them.

Running CARLA

Low FPS rate when running the server in Unreal Editor.

UE4 Editor goes to a low performance mode when out of focus.

Go to Edit/Editor Preferences/Performance in the editor preferences, and disable the "Use Less CPU When in Background" option.

Can't run a script.

Some scripts have requirements. These are listed in files named Requirements.txt, in the same path as the script itself. Be sure to check these in order to run the script. The majority of them can be installed with a simple pip command.

Sometimes on Windows, scripts cannot run with just > script_name.py. Try adding > python script_name.py, and make sure to be in the right directory.

Connect to the simulator while running within Unreal Editor.

Click on Play and wait until the scene is loaded. At that point, a Python client can connect to the simulator as with the standalone simulator.

Can't run CARLA neither binary nor source build.

NVIDIA drivers may be outdated. Make sure that this is not the case. If the issue is still unresolved, take a look at the forum and post the specific issue.

ImportError: DLL load failed: The specified module could not be found.

One of the libraries needed has not been properly installed. As a work around, go to carla\Build\zlib-source\build, and copy the file named zlib.dll in the directory of the script.

ImportError: DLL load failed while importing libcarla: %1 is not a valid Win32 app.

A 32-bit Python version is creating conflicts when trying to run a script. Uninstall it and leave only the Python3 x64 required.

Other

Fatal error: 'version.h' has been modified since the precompiled header.

This happens from time to time due to Linux updates. There is a special target in the Makefile for this issue. It takes a long time but fixes the issue:

  $ make hard-clean
  $ make CarlaUE4Editor

Create a binary version of CARLA.

In Linux, run make package in the project folder. The package will include the project, and the Python API modules.

Alternatively, it is possible to compile a binary version of CARLA within Unreal Editor. Open the CarlaUE4 project, go to the menu File/Package Project, and select a platform. This may take a while.