Convert BVH to C3D

Understanding bvh and c3d file formats

BVH (Biovision Hierarchy) is a widely used file format for storing motion capture data, particularly for character animation in 3D graphics and game development. It contains both the skeleton hierarchy and the motion data for each frame.

C3D (Coordinate 3D) is a standard file format for storing 3D motion capture data, commonly used in biomechanics and clinical gait analysis. It supports not only motion data but also analog data, events, and metadata, making it suitable for scientific and medical applications.

Why convert bvh to c3d?

Converting BVH to C3D is often necessary when you want to use motion capture data from animation or entertainment sources in scientific or clinical analysis tools that require the C3D format. This conversion enables interoperability between animation and biomechanics software.

How to convert bvh to c3d

Direct conversion from BVH to C3D is not natively supported by most software, but specialized tools and workflows can accomplish this:

• MotionBuilder: Import the BVH file, retarget or adjust the skeleton as needed, then export to C3D using plugins or scripts.
• BTK (Biomechanical ToolKit): An open-source library that can be used with MATLAB or Python to convert BVH to C3D. You can use the BTK Python bindings to read BVH data and write it into a C3D file.
• OpenSim: Import BVH files and export motion data, though direct C3D export may require additional steps or plugins.

Recommended software for bvh to c3d conversion

The BTK (Biomechanical ToolKit) is highly recommended for this conversion. It is open-source, supports both formats, and is widely used in the biomechanics community. You can use BTK with Python for scripting the conversion process.

Basic workflow with BTK:

1. Install BTK and its Python bindings.
2. Use a script to read the BVH file and extract motion data.
3. Map the skeleton and marker data appropriately.
4. Write the data to a C3D file using BTK's export functions.

Step-by-step example using BTK in Python

While a full script is beyond this summary, the general steps are:

1. Install BTK: pip install btk
2. Read BVH: btk.bvh.BVHReader('input.bvh')
3. Process and map data to C3D structure.
4. Write C3D: btk.c3d.C3DWriter('output.c3d')

Refer to the BTK documentation for detailed instructions and examples.

Conclusion

Converting BVH to C3D enables the use of animation motion capture data in scientific and clinical applications. BTK is the best tool for this conversion, offering flexibility and robust support for both formats.