Difference between revisions of "Data Export: C3D"

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Revision as of 00:54, 5 December 2015

Back to the Main PageBack to Motive DocumentationBack to Data Export

Tracking data can be exported into the C3D file format. C3D is a binary file format that is widely used especially in biomechanics and motion study applications. Note that common biomechanics applications use a Z-up right-hand coordinate system, whereas Motive uses a Y-up right-hand coordinate system. More details on coordinate systems are described in the later section. Find more about C3D files from https://www.c3d.org/.

C3D Export Options
Options Descriptions
Units Sets which unit is used in exported data.

(Exported unit maybe rescaled to a standard unit when imported into another software.)

Exported Unlabeled Marker Includes unlabeled marker data in the exported C3D file. When set to False, the file will contain data for only labeled markers.
Exported Frame Indices Start at Zero C3D specification defines first frame as index 1. Some applications import C3D files with first frame starting at index 0. Setting this option to true will add a start frame parameter with value zero in the data header.
Axis Can be set either in custom setting or in MotionBuilder Compatible axes convention. Read below for more information.
X Axis Allows customization of the axis convention in the exported file by determining which positional data to be included in the corresponding data set.
Y Axis
Z Axis
Rename Unlabeled As _000X Unlabeled markers will have incrementing labels with numbers _000#.
Use Timecode Includes timecode.
Marker Name Separator. Chooses ":" or "_" for marker name separator

C3D Axes

Since Motive uses a different coordinate system from the system used in common biomechanics applications, it is necessary to modify the coordinate axis to a compatible convention using the C3D export settings. From the custom axis settings, the following changes should be made.

  • X axis converted into negative X
  • Y axis converted into positive Z
  • Z axis converted into positive Y

MotionBuilder (or biomechanics) Compatible Axis Convention This is a convenience option for setting the axes for use in Autodesk MotionBuilder. Even though Motive and MotionBuilder both use the same coordinate system, MotionBuilder assumes biomechanics standards when importing C3D files (negative X axis to positive X axis; positive Z to positive Y; positive Z to positive Y). Accordingly, when exporting C3D files for MotionBuilder use, set the Axis setting to MotionBuilder Compatible, and the axes will be exported using the following convention:

  • Motive: X axis → Set to negative X → Mobu: X axis
  • Motive: Y axis → Set to positive Z → Mobu: Y axis
  • Motive: Z axis → Set to positive Y → Mobu: Z axis
C3D Axis.png
Axis Conversion in C3D Files