opentrack: turn your head, turn the cockpit

Rewritten from FaceTrackNoIR, and older than it looks

opentrack is a program for tracking the user's head rotation and transmitting it to flight simulation software and military-themed video games, and the credits section tells its genealogy with unusual precision, Wim Vriend's FaceTrackNoIR served as the initial codebase, and while the code was almost entirely rewritten, many of its ideas were retained. The maintainer listed first in chronological order is Stanisław Halik, surrounded by two decades of named contributors for specific trackers and translations. The README also apologizes for a long-standing naming conflict with opentrack.ch, the railway planning software that had the name first, a courtesy most projects would not bother with. Releases are annual and dated, opentrack-2026.1.0 on the last day of 2025, preceded by 2024.1.1 and 2023.3.0, with the repository pushed on 2026-09-21, and almost all code is ISC licensed with no copyleft.

Sixteen ways to sense a head

The tracking input list is the project's personality, a hardware museum where everything still works. PointTracker reads FreeTrack-like light points through a camera, Patrick Ruoff's design, and the Aruco tracker reads a marker printed on paper. Dedicated devices arrive as the Oculus Rift, Razer Hydra, Intel RealSense, Tobii eye tracker and Wiimote. Relay inputs cover the distributed cases, plain UDP from another computer, FreePIE Android apps over UDP, and a Windows Phone tracker speaking the opentrack protocol. Maker hardware is first class, Arduino with the custom Hatire firmware, and BBC micro:bit, LEGO and SensorTag devices through the Smalltalk-based S2Bot. The modern end is represented by NeuralNet Tracker, AI-based head pose estimation with ordinary webcams, Eyware Beam, and XReal One glasses, the README noting the One Pro probably works too. Joystick analog axes round out the list for the truly improvised setup. What the list demonstrates is an accumulation strategy rather than a curation strategy, trackers are added as hardware appears and nothing documented has been removed, so a drawer of decade-old peripherals remains usable precisely because this project kept the adapter alive. For a newcomer the practical reading is that the cheapest viable setup is a webcam plus either printed markers or the neural tracker, and the ceiling is dedicated eye-tracking hardware.

Ten protocols on the way out

Outputs target the simulator ecosystem's actual interfaces. SimConnect serves the newer Microsoft Flight Simulator on Windows, and FSUIPC reaches back to Microsoft Flight Simulator 2002 and 2004, a twenty-year compatibility span few programs can claim. The freetrack protocol has both a native Windows implementation and a Wine glue implementation for Linux and macOS, the latter feeding an X-Plane plugin on Linux. Virtual joystick output works on all three operating systems, UDP relays to another computer, tablet-like mouse output covers touch simulations, FlightGear speaks natively, and SteamVR is reached through a bridge, the OpenVR-OpenTrack project by r57zone. The breadth is the point, whatever combination of game, platform and protocol a player arrives with, the odds are that one column of the matrix already has an implementation in the tree, as the proto-* directories confirm. The two flight simulator bookends deserve emphasis, because supporting FSUIPC for simulators released in 2002 and SimConnect for the current Microsoft Flight Simulator means one piece of tracking software spans the hobby's entire modern history, and a pilot who upgraded through every version kept their head tracker throughout.

Six filters and a tuning guide

Between input and output sits the part that decides whether head tracking feels natural, filtering and shaping. The repository carries six filter implementations as first-class directories, accela, accela-hamilton, alpha-spectrum, ewma2, hamilton and nm, with a spline directory for mapping curves and a pose widget for visualization. The newest, the Alpha Spectrum filter, ships its own parameter guide as filter-alpha-spectrum/README.md, an acknowledgment that filter tuning is where users struggle most. The credits name Donovan Baarda as the filtering and control theory expert, and the Hamilton filter and pose widget improvements carry their own attribution, the texture of a project where each mathematical contribution is a person's work rather than an anonymous commit. Output shaping completes the loop, translating filtered rotation into the curves a specific game prefers.

Credits read as a genealogy

The credits section, ordered chronologically, doubles as the project's history, Chris Thompson for the Rift and Razer Hydra trackers, Xavier Hallade for Intel RealSense, furax49 for the Arduino Hatire firmware, Attila Csipa for the micro:bit, Wei Shuai for the Wiimote, Davide Mameli for Eyware Beam, Khoa Nguyen for the Tobii tracker, and Alexander Orokhovatskiy for the Russian translation and profile repository maintenance. The thanks section extends the story outward, uglyDwarf of linuxtrack for the neighboring project, testers and build fixers for the macOS port, and the Russian community of the IL-2 Sturmovik forums credited with reporting bugs and requesting important features, a reminder that this software's user base is concentrated where combat flight simulation is a culture. OpenCV's authors are thanked last, the computer vision layer beneath several trackers. Read end to end, the two lists describe a project whose development history is inseparable from its community's hardware habits, and they explain the maintenance style, each tracker is someone's contribution that the maintainer carries forward, which is why the roster of names maps one to one onto the feature list.

A plugin API and a self-updating wiki

Extending opentrack is documented at the code level, with the plugin API header, api/plugin-api.hpp, and the tracker test harness, tracker-test/test.h, serving as the guides for writing new modules, and a wiki page covering work on the core. The wiki itself has an unusual maintenance arrangement, edits arrive as pull requests to a separate opentrack/wiki repository, and the user-facing wiki automatically updates itself once commits merge, bringing review discipline to documentation that most wikis lack. The repository layout mirrors the architecture plainly, input sources under input and contrib, every output protocol as its own proto-* directory, each filter its own tree, so a newcomer can locate the seam for a new module without reading the whole codebase. Platform compatibility lives in per-compiler CMake SDK path files, including an ASan-enabled Windows configuration, the fingerprint of a maintainer who debugs seriously.

A warranty disclaimer written with feeling

The license section is ISC for almost all code, with very few proprietary dependencies and no copyleft, and then WARRANTY.txt takes over with one of the more human paragraphs in open source, the code is held to a high-quality standard and written with utmost care, consider this a promise without legal value, and despite doing the best we can not to injure users' equipment, software developers don't want to be dragged to courts for imagined or real issues. The honesty extends to platform status, macOS is described as currently unmaintained while Windows and Linux carry on, and to build instructions that name their era, mingw-w64 or Visual Studio 2015 Update 3 or newer. Windows users get an installer or a portable archive per release, with a documented USB-stick portable mode for carrying a setup to a LAN party, and against commercial systems like TrackIR the trade is straightforward, proprietary hardware with vendor support versus commodity hardware, a community, and no license fee. The gameplay video linked from the README shows the end state, a pilot scanning a virtual sky by turning their head, which is the experience all sixteen inputs and ten outputs exist to deliver.

Editorial conclusion

Use opentrack when you want head tracking for flight simulation or combat games without buying proprietary hardware, since its input list spans everything from a printed marker and a webcam to eye trackers and XReal glasses. Buy a commercial tracking system if you want a supported single-vendor experience, because this is community software whose warranty is explicitly disclaimed. Verify first that your game matches one of the output protocols, that your chosen input device has a working tracker in the current build, and note the macOS port is stated as unmaintained while Windows and Linux receive the annual releases.

Frequently asked questions

Official sources

1. Issues
2. opentrack/opentrack on GitHub
3. README
4. Releases