Visual3D stores motion capture data (e.g. 3D markers) in the Data Tree as a TARGET Data type. A TARGET is a 3 degree of freedom signal. TARGET information is either specified in a C3D file or another file format that has been translated into a C3D file during the process of importing the file.

The ORIGINAL folder contains the POINT data that was stored in the C3D File. The POINT data contains 5 components: x, y, z, residual, and camera contribution. Visual3D displays 4 of these elements:

1. the (x,y,z) components describing the location of the point in 3D space; and
2. the residual component containing information from the motion capture hardware indicating the reliability of the point.

The “camera contribution” is a 7 bit value containing the numbers of the cameras that were used for the reconstruction. This is a legacy value because it only allows data from 7 cameras, so Visual3D doesn't display these values.

Note: Visual3D does not routinely let you modify the signals in this folder.

TARGET marker positions carry with them a residual error computed by the data collection software. This can be treated as the reliability in reconstructing the 3D position of the marker. This marker reliability is a measure of the accuracy of the 3D motion capture system in locating that marker.

Each camera in the motion capture system identifies a ray from the camera to the marker. In an ideal world the ray from all cameras would converge on the centre of the marker, but the world isn't ideal. The residual is a measure of the size of a sphere that contains the point at which all rays were closest to the marker. In other words, big residuals indicate that the motion capture system could not reliably locate the marker.

NOTE: Only residual errors greater than 0 can be interpreted as the accuracy of the point. A reliability of 0 indicates that the file was processed by some unknown process, such as a filter or interpolation. A reliability of -1 indicates that the point was obscured or could not be localized by the motion capture system. A reliability of -1 will be represented internally by Visual3D as DATA_NOT_FOUND.