Many of the companies which build optical motion capture systems have their roots in biomechanical research. They create systems for evaluating everything from an athletes performance to the walk cycles of children who need prosthetics. The C3D file format was originally devised as a format for storing both the raw camera information during the data acquisition phase of laboratory tests as well as the marker motion data derived from them. Oxford Metrics, the makers of the Vicon motion capture system elected to use the C3D format as their native file format for their marker data.

The C3D format is the only one of the ones described here that is binary. Thus simply describing the format, keywords and their meaning will not do. Example data structures are provided to give insight into the structure of the binary file.