Data Tree

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The Signal and Event Processing page is the heart of the data stored in the Visual3D Worksapce.

On this page you can examine the data in your workspace in detail, create graphs to visualize signals (time-variant data values), and visualize motion trials as animated graphics.


The Signal and Event Processing page consists of three main display areas: the data tree, the animation display, and the graphs display.


The data tree presents a hierarchical view of your experimental data, similar to the files-and-folders hierarchy seen on most computer operating systems.

Wherever you see a file-folder icon FolderIcon.gif you can click once with the left mouse button on the small box containing a plus sign (+) to its left to expand it and see what the folder contains, e.g.

ParameterFolderIcon.gif        becomes ParameterFolderExpandedIcon.gif

The black-outlined square box BoxEmpty.gif next to each data item is a checkbox (click once with the left mouse button and it becomes BoxChecked.gif) which allows you to select that item as input to the pipeline (see below). Note that selecting a folder automatically selects all the individual items in that folder.

At the bottom level of the hierarchy are parameters, signals and metrics.


Signals are data items recorded over time by your motion-capture or data-acquisition system.
Mathematically, signals are discretely sampled functions whose independent variable is time. Signals may be scalar-valued (e.g., a single voltage output by a strain gauge) or vector-valued (e.g., (x,y,z) coordinates of a target marker).


Parameters are individual metadata items from a C3D file, which may be as simple as a single number or as complex as a list of names.
In contrast, parameters and metrics are discrete data which do not vary as a function of time or any other variable.


Metrics are quantities computed by Visual3D which in some way collapse the time dimension of signals (e.g., average value of a signal over a duration) or the spatial dimension of models (e.g., center of mass of entire model).
The main distinction between parameters and metrics is that parameters are stored in the c3d file parameter section, whereas metrics are computed by Visual3D.

Different types of data are represented by distinctive icons in the data tree. Points and vector-valued signals whose values are point coordinates are represented by a red sphere icon RedSphere.gif; scalar-valued signals (e.g., analog signals recorded during motion trials) are represented by a graph icon GraphIcon.gif; parameters are represented by three green lines reminiscent of printed text TextIcon.gif; and so on. Note also that every item in the data tree has a name, also referred to as its label.



POINT signals (MoCap markers) stored in the c3d File


ANALOG signals stored in the c3d file


Force Platform Signals computed from the ANALOG signals and the FORCE_PLATFORM parameters in the c3d file

These signals can be modified by changing the C3D Force Platform parameters, or by processing the ANALOG signals.
For the PROCESSED ANALOG signals to be used, the user must select this option under the properties menu item.


The ORIGINAL folder contains all of the Event labels stored in the C3D file, or any Event Labels that the user has created or modified.


The ORIGINAL folder contains a folder of each segment created in the model that contains the kinetic and kinematic data resolved in the Laboratory Coordinate System. These signals exist for reference; they cannot be processed or included in a Report Graph. The LINKMODEL based items use this data to create the LINK_MODEL_BASED signals.


The ORIGINAL folder contains the LINKMODEL based items that have been created.

If the user has elected to use PROCESSED data to create the LINKMODEL based items or if the user has elected not to use PROCESSED datat to create the LINKMODEL based items the resulting signal is in the ORIGINAL folder.


The ORIGINAL folder contains the signal as it was computed originally.


The ORIGINAL folder contains the signal as it was computed originally.




Visual3D can also compute new signals from existing signals; smoothing to filter out noise is a typical example. New signals always go into a new folder, initially named PROCESSED, which is a sibling of the folder containing the signal from which the new one was derived (i.e., the new folder sits at the same level in the data hierarchy).

By default when a signal is processed in Visual3D, the resulting signal is stored in the PROCESSED folder. Note that by default this will over-write and existing signals of the same name in the PROCESSED folder.

Many pipeline commands, however, will allow you to select the output folder for the PROCESSED signals.


If the LINKMODEL_BASED_SIGNAL is processed, the result is placed in the PROCESSED folder. Visual3D remembers how to build the ORIGINAL LINKMODEL_BASED_SIGNALS but has not kept complete track of the processing of the LINKMODEL based signals, so the PROCESSED LINKMODEL_BASED_SIGNALS must be reprocessed every time the LINKMODEL is changed. This is a subtle control from C-MOTION because we don't believe that the LINKMODEL_BASED_SIGNALS should be processed, just to make the signals look good.

Context Menus

Clicking the right mouse button in the data tree will bring up a different context menu depending on the type of data selected. The following context menus are available from the data tree:

EVENT_LABEL - Brings up a context menu to:
Highlight a label on the 2D graphs
Rename a label
Delete a label
TARGET, GRFORCE, COFP, FREEMOMENT - Brings up a context menu to:
Graph the X component of a signal
Graph the Y component of a signal
Graph the Z component of a signal
Graph X, Y and Z components of a signal
Remove all graphs
View signal processing history
ANALOG - Brings up a context menu to:
Graph the signal
Remove all graphs
View signal processing history
Viewing Data


The checkboxes next to each signal is used for signal and event processing. The processes specified in the "Process Signals" or "Process Events" dialog will be performed on the checked signals in the data tree.

Quick Processing

For example, if you want to interpolate and lowpass filter all TARGETs in all files, you would: Bring up the "Process Signals" dialog
Add an Interpolate, and a Lowpass Filter process to the "Signal Processing" list.
Set the files pulldown to "All Files"
Check the ORIGINAL checkbox under TARGET (All signals are selected).
Click the "Process" button in the "Process Signals" Dialog
Now all the TARGETs should be interpolated and filtered.
This creates a "PROCESSED" hierarchy under TARGET for the newly processed target data.

Creating a QuickView of Data

Visual3D has several tools to help you view your data. Data View is one of them.

Clicking the left mouse button on a signal will bring up a quickview window for quickly viewing the signals. Clicking the left mouse button on a parameter will bring up a dialog box to view the parameter data.

You can use the Data View to:

Display the raw data for a signal.
Display the graphs for a signals.
View the processing history of a signal.
Export a single signal file to an ASCII file.

To Open and Use Data View

  1. In the data tree on the left, the folder with the original signals should already be open but if it isn't do the following:
    1. Click the + sign next to TARGET folder to open the inner folders.
    2. Click the + sign next to ORIGINAL subfolder. This reveals the contents of the original c3d data file. The red dots are the original signals as labeled by the capture system.
  2. Click on the marker labeled LFT2. with the Left Mouse Button The Data View dialog box will open to the Data Values tab. Here you can see raw data or to export to an ASCII file
    caption caption
  3. On the Data Values tab scroll down to the 24th frame. This is where the data capture system began to collect data for this segment. No data was recorded for this segment in the previous 23 frames. This is not abnormal but it is good to be aware that some markers will not have data for every frame. The reasons for this vary but in this particular case the left foot was not in view of the cameras until the 24 frame. If you see blank frame in the middle of a data set it may be an indication of an erroneous result.
  4. Open the Data Graph tab to view analog graphs. A Quickview can help you to locate obviously incorrect or noisy data.
  5. Open the Signal Processing History tab. Although this tab is currently empty, you can view the processing history of signals here. Visual3D has a command pipeline which allows the user to prepare scripts for processing data. Typically these commands create new data that is derived or interpolated from their original data. Determining the distance between 2 points would be an example of such deriving data. The Signal Processing History tab will tell you what events if any took place on the data.
  6. Close the graph by clicking on the X in the top right-hand corner of the Data View dialog box.

NOTE: The Data View can only be used for one Active file at a time. If you select ALL_FILES or a TAG, the Left Mouse Button click will not do anything.

An exception to this rule is that Metric signals will be displayed for more than one active file.

Displaying a Signal Graph

There is another way to view signal graphs which is different from signal data graphs in the Data View window. These are "interactive" and offer different viewing options of the data which we will explore later. When activated, signal graphs appear on the right-side of the screen and can be used to visualize or add event labels.

To activate an interactive signal graph

  1. In the data tree on the left, if it's not open already open the TARGET folder.
  2. In the ORIGINAL subfolder, right-click the target LFT2.
  3. Open Graph X, Y and Z, and Residual and select New Graph. A set of graphs will open on the right side of the screen.
  4. Place the mouse on any point of one of the graph lines and wait.
    Note: The technique used here is called a mouse over. When you hold the mouse still long enough a yellow tool tip window will appear which displays information about that point on the graph. This corresponds to one frame of data in the motion capture.

Formatting and Animating a Signal Graph

  1. From the View menu, click on View Graph Animation Frame Line. This will create a line on the graph to correspond to a point in an animation. Then click PLAY in the VCR control panel to activate the animation. The vertical line on the signal graph will move along with the 3D figure.
    Note: This may already be up by default.
  2. To format the signal graph, right-click anywhere on the graph to open an options menu. Select Format Graph.
    Note: You can also select multiple graphs first using the CTRL key on your keyboard. Any changes you make will apply to each graph you select.
  3. Enter your desired changes and click Apply. Not all of the options apply to the Signal and Events Processing tab. Below are some of the options that do apply. Other options will be covered later in the Reporting tab.
  • Show Grids: Adds the number of X and or Y grid lines you specify.
  • Tics: Add or subtract tic marks to the axes.
  • Proportional Units: Makes width units equal to length units.
  • Show Points: Shows a small box for each frame on the graph.
  • Show BaseLine: Shows a line at zero.
  • Apply to All Selected: Applies the changes to multiple graphs if you have more than one selected.
  • Apply to Primary Selection Only: Applies the changes to only the first graph you selected if you have multiple graphs selected.

Renaming a Signal

A Right Mouse Click on a signal name in the data tree pops up a menu.


One of the options is to rename the signal.


Deleting a Signal

A Right Mouse Click on a signal name in the data tree pops up a menu.


One of the options is to rename the signal.

Modify the Properties of the Animated Markers

You can modify the size of the targets, landmarks, and joints in three ways.

Marker Size

First, by defining the default size of all markers


Second, by scaling the size in the Data Tree. Select a signal in the data tree using the right mouse button, then select the item "Draw Target Size"


Third, by scaling the size by selecting "Draw Target Properties"


Fourth, use a pipeline command. Note that this uses the same dialog as above.

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