F.A.Q.

It is advised to have at least 30/50GB. Building CARLA from source requires about 25GB of disk space, not counting Unreal Engine installation, which is quite a similar size.

Unreal Engine on Linux requires much more disk space as it keeps all the intermediate files, take a look at this thread about the matter.

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.

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

Many different issues can be dragged during the build installation and finally show here, so here is a list of the most likely reasons why:

• Run Unreal Engine 4.22: Something may have failed when building Unreal Engine. Try running UE editor on its own and check out that it is the 4.22 release.
• Download the assets: The server will not be able to run without the visual content, so this step is mandatory even when building CARLA for the first time. Go to the root CARLA folder and run the script to get the assets: ./Update.sh
• UE4_ROOT is not defined: The environment variable is not set. Remember to make it persistent session-wide by adding it to your ~/.bashrc or ~/.profile, otherwise it will need to be set for every new shell. Run export UE4_ROOT=~/UnrealEngine_4.22 to set the variable this time. Make sure that the path leads to the UE 4.22 main folder.
• Check dependencies: Confirm that everything was installed properly during the first steps of the process. 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 your version of CARLA and try cloning or downloading and extracting it again. Then follow the steps from there.
• 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.

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.

Something went wrong when trying to build CARLA. To know what happened, the build must be done using Visual Studio.

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 (shortcut is F7). The build will fail, but the issues found will be shown below.

This issue occurs when trying to use the make command either to build the server or the client even though CMake is installed with an updated version and added to the environment path. The reason is that the issue is not really related with CMake but a conflict between Visual Studio versions.
Completely erase Visual Studio versions from the system and leave only the Visual Studio 2017 to make sure that everything works properly.

The build is not using the 2017 compiler due to conflict with other Visual Studio or Microsoft Compiler versions. Uninstall the other and rebuild again. If the problem still exists, it may be due to Visual Studio not being 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 the other version of Visual Studio edit %appdata%\Unreal Engine\UnrealBuildTool\BuildConfiguration.xml adding the following lines:

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

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

Many different issues can be dragged during the build installation and finally show here, so here is a list of the most likely reasons why:

• Restart the system: There are many installations going in the Windows build and it would be a great idea to give the system a chance to restart and make sure that everything is updated properly.
• Run Unreal Engine 4.22: Something may have failed when building Unreal Engine. Try running UE editor on its own and make sure that it is the 4.22 release.
• Download the assets: The server will not be able to run without the visual content, so this step is mandatory even when running CARLA for the first time.
• 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 your version of CARLA and try cloning or downloading and extracting it again. Then follow the steps from there.
• 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.

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

This may happen, especially when building for the very first time. Just click on "Accept" to rebuild them.

UE4 Editor goes to a low performance mode when out of focus. It can be disabled in the editor preferences. Go to "Edit->Editor Preferences->Performance" and disable the "Use Less CPU When in Background" option.

Some scripts have requirements that can be found in the files named Requirements.txt in the same path as the script itself. Be sure to get these in order to run the script. The majority of them can simply be installed with a pip install command.

Sometimes on Windows, scripts cannot run just using script_name.py in their directory. Try adding python script_name.py.

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

One of the most common issues is that NVIDIA drivers are outdated in the system where CARLA is intended to run. Please make sure that this is not the case. If the issue is still unresolved, take a look at the forum and feel free to post with the specific issue.

If this message appears when trying to run a script, one of the libraries needed has not been properly installed. As a work around, go to: carla\Build\zlib-source\build
Copy the file named zlib.dll in the directory of the script.

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

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

In Linux, the recommended way is to run make package in the project folder. This method makes a packaged version of the project, including the Python API modules. This is the method used to make a release of CARLA for Linux.

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 takes a while, but it should generate a packaged version of CARLA to execute without Unreal Editor.