The BTK web site is here - http://biomechanical-toolkit.github.io/ - unfortunately it seems that support for the Biomechanics Tool Kit (BTK) has ceased, I have not seen any updates or responses to BTK questions in a while and given the problems that users appear to be having maybe I should remove it from the C3D web site? I would welcome any comments for or against this. Initially the BTK development appeared to be moving to http://www.openma.org/ but unfortunately the web site has not been updated in a while. Note that the free MOKKA C3D viewer application written with BTK is fully functional and is available from the C3D web site for 32/64-bit installations.

If you are looking for an alternative solution, we wrote the C3Dserver originally to give users the ability to access C3D files with only a minimum of understanding of the file format and application programming. A few years later BTK was written with our cooperation as an open source student project based on the C3Dserver. The C3Dserver is still available and can be downloaded and can be installed on 32/64-bit Windows systems from XP through Windows 10 and should be usable with Matlab. The free version is completely functional and not crippled in any way other than being faster if a license is purchased.