C3D.ORG

The biomechanics standard

Updated:

7 May, 2018

The C3D web site is maintained by Motion Lab Systems as a resource for the biomechanics community.

All of the C3D information on this web site is in the public domain and may be copied and freely distributed with other products. The C3D User Manual documenting the C3D format and structure may be copied and supplied with any product that supports C3D.

This web site does not use cookies or collect or store any data from visitors.

Original XHTML 1.0 Strict and CSS2 template by Andreas Viklund

Search the C3D web site

C3D Files supported

The websites listed above all offer products that support C3D files. Please contact us if your product supports the C3D format to request that your website be added to this list.

Brief description of M-files

 

c3dserver.m

itf = c3dserver()

Activates C3DServer as a COM (COM.c3dserver_c3d), and returns 'itf' as a COM object for the server.
openc3d.m

openc3d(itf, getoption, fname)

Loads a C3D file into the C3DServer domain.

itf = variable name used for COM object

getoption = 1 for Windows dialog, other than 1 to enter filename

fname = filename, with or without path and c3d extension

Note: openc3d will handle 'fname' with or without the '.c3d' extension. 'fname' must be entered with directory path unless current MATLAB path is where the file is located.
closec3d.m

closec3d(itf)

Removes C3D file from the C3DServer domain.

itf = variable name used for COM object.
savec3d.m

savec3d(itf, newfname, filetype)

Saves C3D file.

itf = variable name used for COM object

newfname = new filename to save, 'a' to save to open file

filetype = Intel(1), DEC(2), SGI(3), existing type (-1)

Note: 'newfname' and 'filetype' default to the name of the currently open file and the existing filetype if only 'itf' is entered as input. savec3d will handle 'newfname' with or without the '.c3d' extension.

'newfname' can be entered with directory path.
createc3d.m

createc3d(itf,name,vfrt,nfram,nmkr,avr,achn,ftype,dtype,pscal)

Creates C3D file with the input parameters.

itf = variable name used for COM object

name = name given to C3D file

vfrt = video frame rate, must be > 0, default 120

nfram = number of frames, default 500

nmkr = number of markers, not < 0, default 20

avr = analog to video ratio, default 13

achn = number of analog channels, not < 0, default 28

ftype = Intel(1), DEC(2), SGI(3), default 1

dtype = Integer(1), Floating Point(2), default 2

pscal = point data scaling factor, must be > 0, default 0.1

Note: Only requires 2 inputs ('itf' and 'name') if user accepts defaults for other parameters. createc3d will handle 'name' with or without the '.c3d' extension. 'name' can be entered with directory path.
nframes.m

frames = nframes(itf)

Returns integer value of the number of video frames contained in an open C3D file.

itf = variable name used for COM object

frames = integer value of number of video frames in c3d file.
analog2 …

truncated = analog2videoframes(itf, signals, index1, index2)

videoframes.m

Truncates input signals to video frame rate.

itf = variable name used for COM object

signals = array to be truncated

index1 = video start frame index, all frames if not used as an argument

index2 = video end frame index, all frames if not used as an argument truncated = truncated signals array.
get3dtarget.m

XYZPOS = get3dtarget(itf, signalname, residual, index1, index2)

Returns nx4 array containing X,Y,Z trajectory data and residual.

itf = variable name used for COM object

signalname = string name of desired marker

residual = Return matrix with point residual in column 4. 0 or no 3rd argument = false (returns nx3 with XYZ data only). 1 = true (returns nx4 with XYZ and residuals)

index1 = start frame index, all frames if not used as an argument

index2 = end frame index, all frames if not used as an argument

XYZPOS = nx3/4 matrix with n frames and X, Y, Z, and/or residual as columns.
get3dtargets.m

XYZPOS = get3dtargets(itf, residual, index1, index2)

Returns structure containing all X,Y,Z trajectory data and residuals if chosen.

itf = variable name used for COM object

residual = Return matrix with point residual in column 4. 0 or no 3rd argument = false (returns nx3 with XYZ data only). 1 = true (returns nx4 with XYZ and residuals)

index1 = start frame index, all frames if not used as an argument

index2 = end frame index, all frames if not used as an argument

XYZPOS = structure with target fields, x,y,z and/or residual columns.
getanalog …

ACHANNEL = getanalogchannel(itf, signalname, index1, index2)
channel.m

Returns nx1 array containing analog data. The returned analog data is scaled with offsets removed, but is in the force plate coordinate system.

itf = variable name used for COM object

signalname = string name of desired signal

index1 = start frame index, all frames if not used as an argument

index2 = end frame index, all frames if not used as an argument

ACHANNEL = nx1 matrix of analog data.
getanalog …

ACHANNEL = getanalogchannels(itf, index1, index2)

channels.m

Returns structure with nx1 analog data fields. The returned analog data is scaled with offsets removed, but is in the force plate coordinate system.

itf = variable name used for COM object

index1 = start frame index, all frames if not used as an argument

index2 = end frame index, all frames if not used as an argument ACHANNEL = structure with nx1 matrix of analog data fields (+units).
getemg …

EMG = getemgchannels(itf,chanstart,chanend,type,index1,index2)

channels.m

Returns emg data in raw or processed forms.

itf = variable name used for COM object

chanstart = first emg channel

chanend = last emg channel type = 0 or no input for raw, 1 for FWR, 2 for LE (6Hz dual-pass)

index1 = start frame index, all frames if not used as an argument

index2 = end frame index, all frames if not used as an argument EMG = stucture with channel fields.