ROTATION DATA TYPE
C-Motion introduced the ROTATION data type in 2019 to handle the storage of a 4x4 Transformation matrix containing the 6 DOF information for a Sensor or Segment.
This was introduced to handle C-Motion DSX results and to handle Theia Markerless Results
Each signal contains a 4x4 Rotation matrix that transforms a signal from the local coordinates of the sensor/segment to the laboratory coordinates
- [R4x4] [Vlocal4x1] = [Vlab4x1]
The signals are stored in column major format in the c3d file, but displayed and used in Visual3D in the command row major format of Visual3D.
ROTATION signals can be used to define LANDMARKS, define SEGMENTS, and to Track SEGMENTS.
C3D_ROTATION_PARAMETERS
The ROTATION GROUP
- USED = Number of ROTATION signals
- DATA_START = Block number for the start of the Data Block
- RATE = Sampling Rate
- RATIO = Ratio of ROTATION sample rate to POINT sample rate
- FRAMES = Number of frames of data
- LABELS = Name of each ROTATION signal
- DESCRIPTIONS = Description of each ROTATION signal
C3D_ROTATION_DATA
- Each signal is represented by 17 float values (there is no physical meaning for scaling integer data)
- 16 entries for the 4x4 ROTATION matrix. stored as columns
- 1 entry for a reliability metric.