# F.A.Q.

Some of the most common issues regarding CARLA installation and builds are listed here. Some more can be found in the [GitHub issues](https://github.com/carla-simulator/carla/issues?utf8=%E2%9C%93&q=label%3Aquestion+) for the project. In case you don't find your doubt listed here, have a look in the forum and feel free to ask there.

<div class="build-buttons">
<p>
<a href="https://forum.carla.org/" target="_blank" class="btn btn-neutral" title="Go to the CARLA forum">
CARLA forum</a>
</p>
</div>

---

## System requirements

* [Expected disk space to build CARLA.](#expected-disk-space-to-build-carla)
* [Recommended hardware to run CARLA.](#recommended-hardware-to-run-carla)

---

## Linux build

* ["CarlaUE4.sh" script does not appear when downloading from GitHub.](#carlaue4sh-script-does-not-appear-when-downloading-from-github)
* ["make launch" is not working on Linux.](#make-launch-is-not-working-on-linux)
* [Cloning the Unreal Engine repository shows an error.](#cloning-the-unreal-engine-repository-shows-an-error)
* [AttributeError: module 'carla' has no attribute 'Client' when running a script.](#attributeerror-module-carla-has-no-attribute-client-when-running-a-script)
* [Cannot run example scripts or "RuntimeError: rpc::rpc_error during call in function version".](#cannot-run-example-scripts-or-runtimeerror-rpcrpc_error-during-call-in-function-version)

---

## Windows build

* ["CarlaUE4.exe" does not appear when downloading from GitHub.](#carlaue4exe-does-not-appear-when-downloading-from-github)
* [CarlaUE4 could not be compiled. Try rebuilding it from source manually.](#carlaue4-could-not-be-compiled-try-rebuilding-it-from-source-manually)
* [CMake error shows even though CMake is properly installed.](#cmake-error-shows-even-though-cmake-is-properly-installed)
* [Error C2440, C2672: compiler version.](#error-c2440-c2672-compiler-version)
* ["make launch" is not working on Windows.](#make-launch-is-not-working-on-windows)
* [Make is missing libintl3.dll or/and libiconv2.dll.](#make-is-missing-libintl3dll-orand-libiconv2dll)
* [Modules are missing or built with a different engine version.](#modules-are-missing-or-built-with-a-different-engine-version)

---

## Running Carla

* [Low FPS rate when running the server in Unreal Editor.](#low-fps-rate-when-running-the-server-in-unreal-editor)
* [Can't run a script.](#cant-run-a-script)
* [Connect to the simulator while running within Unreal Editor.](#connect-to-the-simulator-while-running-within-unreal-editor)
* [Can't run CARLA neither binary nor source build.](#cant-run-carla-neither-binary-nor-source-build)
* [ImportError: DLL load failed: The specified module could not be found.](#importerror-dll-load-failed-the-specified-module-could-not-be-found)
* [ImportError: DLL load failed while importing libcarla: %1 is not a valid Win32 app.](#importerror-dll-load-failed-while-importing-libcarla-1-is-not-a-valid-win32-app)

---

## Other

* [Fatal error: 'version.h' has been modified since the precompiled header.](#fatal-error-versionh-has-been-modified-since-the-precompiled-header)
* [Create a binary version of CARLA.](#create-a-binary-version-of-carla)

---

<!-- ======================================================================= -->
## System requirements
<!-- ======================================================================= -->

###### Expected disk space to build CARLA.

> It is advised to have at least 30-50GB free. Building CARLA requires about 25GB of disk space, plus Unreal Engine, which is similar in size. 
>
> Unreal Engine on Linux requires much more disk space as it keeps all the intermediate files. [This thread](https://answers.unrealengine.com/questions/430541/linux-engine-size.html) discusses the matter.

<!-- ======================================================================= -->

###### Recommended hardware to run CARLA.

> CARLA is a performance demanding software. At the very minimum it requires a 4GB GPU or, even better, a dedicated GPU capable of running Unreal Engine.  
>
> Take a look at [Unreal Engine's recommended hardware](https://wiki.unrealengine.com/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](build_linux.md) to build CARLA from source.  
> 
> To run CARLA using `CarlaUE4.sh`, follow the [quick start installation](start_quickstart.md).

<!-- ======================================================================= -->

###### "make launch" is not working on Linux.

> Many different issues can be dragged out during the build installation and will manifest themselves 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 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](https://forum.carla.org/) so the team can get to know more about them.   

<!-- ======================================================================= -->

###### Cloning the Unreal Engine repository shows an error.

> __1. Is the Unreal Engine account activated?__ The UE repository is private. In order to clone it, create the [UE](https://www.unrealengine.com/en-US/) account, activate it (check the verification mail), and [link your GitHub](https://www.unrealengine.com/en-US/blog/updated-authentication-process-for-connecting-epic-github-accounts) account.  
> 
> __2. Is git properly installed?__ Sometimes an error shows incompatibilities with the `https` protocol. It can be solved easily by uninstalling and reinstalling git. Open a terminal and run the following commands:
>
>      $ sudo apt-get remove git #Uninstall git
>      $ sudo apt install git-all #install git
> 

<!-- ======================================================================= -->

###### AttributeError: module 'carla' has no attribute 'Client' when running a script.

> Run the following command.
> 
> 
>       $ pip3 install -Iv setuptools==47.3.1
>  
>
> And build the PythonAPI again. 
> 
>
>      $ make PythonAPI
>
>
> Try to build the docs to test if everything is running properly. A successful message should show.
>
>      $ make PythonAPI.docs

<!-- ======================================================================= -->

###### Cannot run example scripts or "RuntimeError: rpc::rpc_error during call in function version".

> ![faq_rpc_error](img/faq_rpc_error.jpg)
>
> If running a script returns an output similar to this, there is a problem with the `.egg` file in the PythonAPI. 
> 
> First of all, open `<root_carla>/PythonAPI/carla/dist`. There should be an `.egg` file for the corresponding CARLA and Python version you are using (similar to `carla-0.X.X-pyX.X-linux-x86_64.egg`). Make sure the file matches the Python version you are using. To check your Python version use the following command.  
> 
> 
>       $ python3 --version # CARLA no longer provides support for Python2, so we are dismissing it here
> 
>
> If either the file is missing or you think it could be corrupted, try rebuilding again.  
>
>      $ make clean
>      $ make PythonAPI
>      $ make launch
>
>  
> Now try one of the example scripts again. 
>
>      $ cd PythonAPI/examples
>      $ python3 dynamic_weather.py
>
> If the error persists, the problem is probably related with your PythonPATH. These scripts automatically look for the `.egg` file associated with the build, so maybe there is another `.egg` file in your PythonPATH interfering with the process. Show the content of the PythonPATH with the following command.  
>
>
>      $ echo $PYTHONPATH
>
> Look up in the output for other instances of `.egg` files in a route similar to `PythonAPI/carla/dist`, and get rid of these. They probably belong to other instances of CARLA installations. For example, if you also installed CARLA via *apt-get*, you can remove it with the following command, and the PythonPATH will be cleaned too.  
>
>      $ sudo apt-get purge carla-simulator
>
> Ultimately there is the option to add the `.egg` file of your build to the PythonPATH using the `~/.bashrc`. This is not the recommended way. It would be better to have a clear PythonPATH and simply add the path to the necessary `.egg` files in the scripts.  
>
> First, open `~/.bashrc`.
>
>      $ gedit ~/.bashrc
>
> 
> Add the following lines to `~/.bashrc`. These store the path to the build `.egg` file, so that Python can automatically find it. Save the file, and reset the terminal for changes to be effective.
>
> ```
> export PYTHONPATH=$PYTHONPATH:"${CARLA_ROOT}/PythonAPI/carla/dist/$(ls ${CARLA_ROOT}/PythonAPI/carla/dist | grep py3.)"
> export PYTHONPATH=$PYTHONPATH:${CARLA_ROOT}/PythonAPI/carla
> ```
> 
> After cleaning the PythonPATH or adding the path to the build `.egg` file, all the example scripts should work properly.  

---

## 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](build_windows.md) to build CARLA from source. To directly get the `CarlaUE4.exe`, follow the [quick start instructions](start_quickstart.md).  

<!-- ======================================================================= -->

###### 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.
>
> Different issues may result in this specific error message. The user [@tamakoji](https://github.com/tamakoji) solved a recurrent case where the source code hadn't been cloned properly and the CARLA version could not be set (when downloading this as a .zip from git).  
>
> *   __Check the `Build/CMakeLists.txt.in`.__ If it shows as `set(CARLA_VERSION )` do the following:  
>
> __1.__ Go to `Setup.bat` line 198.  
>
> __2.__ Update the line from: 
> 
> ```
> for /f %%i in ('git describe --tags --dirty --always') do set carla_version=%%i
> ```
> 
> to:
> 
> ```
> for /f %%i in ('git describe --tags --dirty --always') do set carla_version="0.9.9"
> ```

<!-- ======================================================================= -->

###### CMake error shows even though 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 out during the build installation and manifest themselves like this. Here is a list of the most likely reasons why: 
> 
> * __Restart the computer.__ There is a lot going on during 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 version 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](https://forum.carla.org/) so the team can get to know more about them.

<!-- ======================================================================= -->

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

> Download the [dependencies](http://gnuwin32.sourceforge.net/downlinks/make-dep-zip.php) 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 `> python3 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](https://forum.carla.org/) 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. 

---