MoMo R5.1: Visualize C3D files

1. Contents
2. Setup
3. Preferences
4. Sessions
5. Command line
6. Models
7. C3D: 7.1fC3D toolbox
8. Administration
9. Changes

7.1 C3D toolbox functions

The fC3D toolbox is a collection of function for reading and visualisation of C3D files. The files are imported to a Matlab struct at first. Afterwards the user can export selected trajectories, GRFs, analog signals or parameters to arrays and use them for individual processing. The contents of C3D files can be displayed as 2D diagrams using the GUI ShowC3D. 3D animations are created by ShowC4D, which allows a spatial navigation as in the Vicon software and creating objects like makers, connections, planes, arrows and tripods. The animations can be saved as picture files, AVI or animated GIF. An ASCII-files export can be freely configured by the user.
The modification and creation of C3Ds is implemented in general, but not recommended for standard use, because Vicon's interpretation of C3D format is fragil. However, renaming trajectories or swapping signals of analog channels is safe. Special formats used by Vicon to enhance the C3D standard are considered: more than 255 trajectories, more than 65535 frames (which are just 262 seconds at 250 Hz).
Time-critical function are implemented in C to increase the speed.
The fC3D toolbox was designed for clinical studies and diagnosis. In consequence the reliability and stability is ver important. The different functions have been tested ober several years in different labs under Matlab 6.5, 2008b and 2009a and with different versions of Vicon WorkStation and Nexus. An exahustive selftest allows a quality-control on the computer system of the users.
The fC3D toolbox is shipped with MoMo, but it is available as standalone version also.

7.2 ShowC3D: C3D as diagrams

The function ShowC3D let the user inspect the contents of one or more C3D files in details: Signals of force plates, evaluated GRF vector components, torsion around Z, force insertion point, EMG signals, trajectories of markers and evaluated 3D variables, group and parameter data.
ShowC3D dialogFile: Forces: EMG: Parameters: Trajectories: Buttons:
Created diagrams:
Some output diagrams contain event markers. They can be dragged vertically with the mouse using the small arrow handle or text "Events" right from the diagrams. A right-click on this handle toggles the visibility of vertical lines through the events (new: 15-Jun-2010). If the event handle has vanished after zooming into a diagram, disabling and re-enabling the events in the context menu let them appear again.
If a curve contains (invisible) Inf or NaN values, the text 'Gaps!' is displayed as warning. The context menu of this text (right-click) displays the names of the affected trajectories. all frames with gaps are colored in light yellow, if "Gaps" flag is enabled in the context menu of the diagram or the figure.
Several jobs can be started through the context menu of the figures (right-click) depending on the data: the visibility of gaps and events can be toggled, values of the trajectories can be copied and simple statistics can be displayed.
The right-most icon in the toolbar toggles the visibility of the legend (do not use the less powerful legend-icon of Matlab 7). The legend can be moved using the mouse.

7.3 ShowC4D: C3D as animation

The function ShowC4D visualizes the contents of C3D files as animated 3D objects. It can be called from the command line, from MoMoG or with additionally created objects from the model scripts of MoMo.
The file and the ShowC4D-model can be defined as optional input arguments: ShowC4D(FileName, Model).
ShowC4D uses a model to identify markers and other objects in the variables included in a C3D. These models are implemented as simple Matlab functions and users can add own models.
ShowC4D dialog Spatial navigation:
UI-controls: Draw menu: Show menu: Model menu: Help menu:
ShowC4D: export dialog Export dialog:
Models for ShowC4D:
The relation between variables and 3D objects is defined in models, which are implemented as simple Matlab functions. These functions are store in the folder "ShowC3D4_Model", they can be modified and new models can be created: Use the Model: Edit menu. Then a new file is created in the correct path. See the template file for help.
All versions 4.xy of ShowC4D use the models in the folder "ShowC3D4_Model".
ShowC4D is not limited to C3D files as input. It accepts structs with a well defined format (e.g. when called from MoMo). Further file types can be inserted as plugins. Ask the author for help.
General tips:
Reset the styles and window positions: ShowC4D $clear
Self test: ShowC4D $test
Arguments to show a trial with evaluation of MoMo: C4D, C4Dadd.
The freeware program ImageMagick creates small and nice animated GIFs. The needed command is written to the command line after the export of a movie as series of PNGs.
Author: © Jan Simon, Imprint / Impressum   File: Help/momo_5.1/c3d.html    24-Nov-2018   MoMo: 5.1.34