How to Use the Scale Tool

Last updated: Jul 07, 2022 by Ayman HabibVersion comment

The topics covered in this section include:

How to Use the GUI

The Scale Tool is accessed by:

Select Tools → Scale Model... from the OpenSim main menu bar.
You need the model you want to be scale to be current. To learn how to make a model current visit Opening, Closing, and Using the Navigator Window.

The Scale Tool is controlled by a window with three tabbed panes. The Settings Pane is used to specify parameters relating to the subject data, the generic model, and how the model is to be scaled. The Scale Factors Pane is used to specify the scale factors for each segment. The Scale Static Pose Weights Panel pane is used to specify weights on marker positions and joint angles for solving an inverse kinematics problem for the static pose. The inverse kinematics solution for the static pose is used to place the virtual markers on the model so that they coincide with the measured marker locations on the subject.

The Control Panel

At the bottom of all the Tool dialog windows are four buttons, located in what we call the Control Panel.

The Load and Save buttons are used to load or save settings for the tool.
The Run button starts execution.
The Close button closes the window.
The Help button takes you to the relevant section of the User Guide.

Note that the Close button can be clicked immediately after execution has begun; the execution will complete even though the window has been closed.

If you click Load…, you will be presented with a file browser that displays all files ending with the .xml suffix. You may browse for an appropriate settings file (e.g., subject01_Forward_Setup.xml or subject01_Scale_Setup.xml)) and click Open. The tool will then be populated with the settings in that setup file.
If you have manually entered or modified settings, you may save those settings to a file for future use. If you click Save…, a Save dialog box will come up in which you can specify the name of the settings file. The name you specify for the file should have a suffix of .xml. Click Save to save the settings to file.
After you click Save, you may be presented with another dialog box that asks you whether or not you would like to save some of the settings to separate external files. This can be useful if you would like to reuse those settings for other trials or subjects. Check the boxes of the settings that you'd like to save to external files and specify the names of these files. All of these files should have a suffix of .xml.

The Settings Pane

The Settings pane is used to specify parameters related to the subject data, the generic model, and how the model is to be scaled. The panel is organized into four main sections, described below.

Generic Model Data

The section for Generic Model Data displays uneditable information about the generic model that is to be scaled. It gives the model name, the model mass, and whether or not a marker set is included as part of the model).

Subject Data Section

The section for Subject Data displays editable information that allows you to specify the name of the new model that will be generated, the subject's total mass, and whether or not to add markers to the model from an external marker set.
If you select the check box next to Add markers from file, you will be required to specify a settings file that contains markers.
You may use the folder button to browse for a marker set. Once a marker set is read in, the number of markers in the marker set will be displayed just below the file name.