Contributing to CARLA

We are more than happy to accept contributions!

How can I contribute?

  • Reporting bugs
  • Feature requests
  • Improving documentation
  • Code contributions

Reporting bugs

Use our issue section on GitHub. Please check before that the issue is not already reported, and make sure you have read our Documentation and FAQ.

Feature requests

Please check first the list of feature requests. If it is not there and you think is a feature that might be interesting for users, please submit your request as a new issue.

Improving documentation

If you feel something is missing in the documentation, please don't hesitate to open an issue to let us know. Even better, if you think you can improve it yourself, it would be a great contribution to the community!

We build our documentation with MkDocs based on the Markdown files inside the "Docs" folder. You can either directly modify them on GitHub or locally in your machine.

Once you are done with your changes, please submit a pull-request.

TIP: You can build and serve it locally by running mkdocs in the project's main folder

$ sudo pip install mkdocs
$ mkdocs serve

Code contributions

So you are considering making a code contribution, great! we love to have contributions from the community.

Before starting hands-on on coding, please check out the projects page to see if we are already working on that, it would be a pity putting an effort into something just to discover that someone else was already working on that. In case of doubt or to discuss how to proceed, please contact one of us (or send an email to carla.simulator@gmail.com).

Where can I learn more about Unreal Engine?

A basic introduction to C++ programming with UE4 can be found at Unreal's C++ Programming Tutorials. Then, if you want to dive into UE4 C++ development there are few paying options online. The Unreal C++ Course at Udemy it's pretty complete and there are usually offers that make it very affordable.

What should I know before I get started?

Check out the "CARLA Design" document to get an idea on the different modules that compose CARLA, and chose the most appropriate one to hold the new feature. We are aware the developers documentation is still scarce, please ask us in case of doubt, and of course don't hesitate to improve the current documentation if you feel confident enough.

Are there any examples in CARLA to see how Unreal programming works?

You can find an example of how C++ classes work in UE4 in ASceneCaptureToDiskCamera (and its parent class ASceneCaptureCamera). This class creates an actor that can be dropped into the scene. In the editor, type "Scene Capture To Disk" in the Modes tab, and drag and drop the actor into the scene. Now searching for its detail tab you can find all the UPROPERTY members reflected. This shows the basic mechanism to use C++ classes in Unreal Editor.

For a more advanced example on how to extend C++ classes with blueprints, you can take a look at the "VehicleSpawner" blueprint. It derives from the C++ class AVehicleSpawnerBase. The C++ class decides where and when it spawns a vehicle, then calls the function SpawnVehicle(), which is implemented in the blueprint. The blueprint then decides model and color of the vehicle being spawned. Note that the blueprint can call back C++ functions, for instance for getting the random engine. This way there is a back-and-forth communication between C++ code and blueprints.

Coding standard

Please follow the current coding standard when submitting new code.

Pull-requests

Once you think your contribution is ready to be added to CARLA, please submit a pull-request.

Try to be as descriptive as possible when filling the pull-request description. Adding images and gifs may help people to understand your changes or new features.

Please note that there are some checks that the new code is required to pass before we can do the merge. The checks are automatically run by the continuous integration system, you will see a green tick mark if all the checks succeeded. If you see a red mark, please correct your code accordingly.

Checklist
  • [ ] Your branch is up-to-date with the master branch and tested with latest changes
  • [ ] Extended the README / documentation, if necessary
  • [ ] Code compiles correctly
  • [ ] All tests passing
    • [ ] make check
    • [ ] pylint --disable=R,C --rcfile=PythonClient/.pylintrc PythonClient/carla PythonClient/*.py
    • [ ] cppcheck . -iBuild -i.pb.cc --enable=warning