Specialized programmers, researchers
Edit your C3D files.
Bridge reads, writes and modifies acquisition files, keeping the familiar BTK API so your existing work carries over without friction.
Why the reboot
A trusted toolkit, brought up to date
For more than 15 years the Biomechanical ToolKit (BTK) has supported thousands of students and professionals. As computing evolves (Apple Silicon, and the need for unofficial C3D features like rotational data), we are rebooting BTK as Bridge, supported by Moveck, so the tool stays sustainable for the long term.
Free
No licence to buy
Built on the Moveck platform and offered free of charge, so anyone can use it.
200+
Peer-reviewed papers
Since 2009, BTK has been cited in over 200 scientific papers across the academic community.
15+ yrs
Proven in the field
Thousands of students and professionals, plus many industrial users, have relied on the toolkit.
New
C3D rotation and Apple Silicon
Direct access to rotation data in C3D from markerless systems, on modern architectures, with user-driven fixes.
The idea
“The output of past, present and future motion-capture technology, readable in the same way.”
The heritage
More than fifteen years of open-source biomechanics
Bridge is not a new library with an old name. It is the continuation of a line of open-source tools that the biomechanics community has built and relied on since 2009: BTK, then Mokka, then OpenMA, then pyCGM2. Each one solved a piece of the same problem, which is that movement data arrives in a dozen formats from a dozen vendors and none of them agree.
BTK was the foundation, and it is the one that ended up inside everyone else's work. It has been cited in over 200 peer-reviewed papers, it has been taught to thousands of students, and it quietly runs inside laboratory pipelines that nobody has touched in a decade. That is exactly the problem a reboot has to respect: code that old is load-bearing, and breaking it is not a trade anyone would accept for a nicer API.
So Bridge keeps the API. The MATLAB wrapper definition carries over unchanged and the Python side mirrors it, function for function, using the original unit tests plus expanded reference data to prove it. What changes is underneath: Apple Silicon support, access to the rotation data that markerless systems write into C3D outside the official specification, and a maintained release cadence with a team behind it.
The API
Three samples, and the shape they prove
Bridge is handle-based free functions, never method style. You open an acquisition, you pass the handle around, you close it.
from btk import btkReadAcquisition, btkGetPoint, btkCloseAcquisition
acq = btkReadAcquisition("trial.c3d")
values, info = btkGetPoint(acq, "RASI") # (n, 3) array; occlusion is NaN
btkCloseAcquisition(acq)Every marker at once, keyed by label, with the sampling information beside it:
from btk import btkReadAcquisition, btkGetMarkers, btkCloseAcquisition
acq = btkReadAcquisition("trial.c3d")
markers, info = btkGetMarkers(acq)
print(len(markers), info.frequency)
btkCloseAcquisition(acq)Read, modify, write back. This is the half that makes it an SDK rather than a reader:
from btk import btkReadAcquisition, btkWriteAcquisition, btkCloseAcquisition
acq = btkReadAcquisition("trial.c3d")
btkWriteAcquisition(acq, "trial-clean.c3d")
btkCloseAcquisition(acq)What Bridge gives you
Familiar, reliable and free
A seamless move from BTK, on the platforms and languages you already use, and free.
MATLAB and Python
Read, write and modify acquisition files, with all functions accessible through both the MATLAB and Python wrappers.
Windows and macOS
Available on both Windows and macOS, so a wider range of users can work on their preferred platform.
Backward compatible with BTK
We kept the MATLAB wrapper definition and adapted it for Python, with full documentation to support a smooth transition.
Ongoing support
A dedicated team delivers bug fixes and keeps pace with technology, using the original unit tests and expanded reference data.
Built for large-scale data
Bridge handles massive data processing with ease and complements Pipe, Cleanse and Explore: the Moveck applications made for fast, efficient data management.