The following Object-Specific Commands are available:

Model Node

When a model is loaded into OpenSim, OpenSim creates a tree representing the objects comprising this model and adds it to the existing tree displayed in the Navigator window. The node for the model will show the model name (as specified inside the .osim file). If the model is marked as "current," the model name is displayed in bold.

The following options are available from the context menu associated with the node for the model. You can access the menu by clicking the right mouse button on the node. 

To set the model offset value, select the Display -> Model Offset… option from the main OpenSim menu bar. This brings up the dialog box shown below. The default display offset is chosen so that the new model does not overlap with existing models, and is based on the size of a bounding box containing all the models already loaded in OpenSim. You can change this offset, for example, to overlay models on top of each other or to put them far apart, by entering new values in the Model Offset dialog box. The offset value is always relative to the model's current position.

This display offset is a display only property. The model itself is never affected by the changes to the display offset.


Motion Node

When a motion is loaded into OpenSim, it is added to the existing tree in the Navigator window under the Motions node. The node for the motion will show the motion name. If the motion is marked as "current," its name is displayed in bold.

The following options are available from the drop down (context) menu associated with the node for the motion. You can access the menu by clicking the right mouse button on the node.

Displaying Coordinate Axes for Body and Joint Nodes

The display of the coordinate axes for each body is controlled by clicking the right mouse button on the associated node for that body and selecting the Show Axes option. The Show Axes option is a toggle. A check next to it indicates that the coordinate axes are already being displayed. In this case, clicking on the option will turn off the coordinate axes display. If the axes are not being displayed and the Show Axes option is clicked, then the axes will appear.

For joint nodes, there are two similar options: Toggle Child Frame and Toggle Parent Frame. As with the Show Axes option for a body node, the Toggle Child Frame and the Toggle Parent Frame options are toggle buttons, as their names indicate, accessible via the right mouse button. You click the option to turn it on and click it again to turn it off. The two frames (child and parent) are associated with the two frames the joint connects.

The coordinate axes for both body and joint nodes appear as a set of three orthogonal lines, colored red (x-axis), green (y-axis), blue (z-axis). 

Enabling and Disabling Force, Muscle and Constraint Nodes

All force, muscle  and constraint nodes can be enabled or disabled via their Enable option. This is a toggle button, accessed by clicking the right mouse button on the node.  

If the force, muscle or constraint is enabled, a check appears next to the Enable option. To disable the force, muscle or constraint, just click on Enable. To turn the force, muscle or constraint back on, click on Enable again.

Displaying the Center of Mass of Individual Bodies and the Model

Nodes corresponding to individual bodies have another option to toggle the display of the center of mass. Turning this toggle menu choice on will cause the Center-of-mass of the corresponding body to be displayed as a solid green sphere. You can view the entire system's center of mass by clicking the right mouse button on the Bodies node and selecting Show Mass Center; this is visualized as a larger green sphere.

This screenshot shows the body center of mass for the model's right ulna (on the left in the image), and the system's center of mass (larger green sphere). Note that if the center of mass happens to be a location embedded within the geometry of a body, you may need to adjust transparency or switch some Geometry display to wireframe.


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