CiThruS2 (See-Through Sight 2) is a simulation framework and virtual city environment built in Unreal Engine 5 to aid in testing and developing various traffic-related systems, drone systems and vision-based systems. The environment is based on the real suburb of Hervanta in Tampere, Finland, and it supports features such as simulated cars, pedestrians, cyclists, weather, seasonal effects, a changeable time of day, as well as real-time video streaming, recording, and receiving.
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Ultra Video Group has a public Discord server where you can ask questions about CiThruS2 (and other UVG projects). You can join the server here.
The GitHub wiki tab has a section on how to get started with using CiThruS2.
https://github.com/ultravideo/CiThruS2/wiki/Getting-Started
Old versions of CiThruS2 for older Unreal Engine versions are available on separate branches. They do not have the latest features and will no longer be updated, but they are otherwise usable. To avoid version conflicts while switching branches, we recommend first deleting all files generated by the setup script and Unreal Engine and then regenerating them from scratch on the new branch.
If you are using CiThruS2 in your research with a focus on ground vehicles and traffic, please cite the following paper:
A. Leppäaho, P. Sjövall, G. Gautier, and J. Vanne, “CiThruS2: Open-source simulation framework for vision-based ADAS development,” in Proc. IEEE Int. Automated Vehicle Validation Conf., Baden-Baden, Germany, Sep.—Oct. 2025.
If you are using CiThruS2 in your research with a focus on UAVs/drones, please cite the following paper:
E. Gałązka, A. Leppäaho, and J. Vanne, “CiThruS2: open-source virtual environment for simulating real-time drone operations and piloting,” in Proc. IEEE Int. Automated Vehicle Validation Conf., Austin, Texas, USA, Oct. 2023.
In other kinds of research, please cite the one you believe to be the most appropriate. If you're not sure which one to choose, we recommend the most recent paper.