3.2 Model reference system

The Model Reference System is centered at the midpoint between the model's hips and is associated with its orientation. In the interface, however, it is shown projected onto the floor (Figure 2). The X axis extends horizontally toward the model's right, and the Z axis extends vertically upward. The Y axis is perpendicular to the other two and positive toward the front of the model.

When the model's global orientation changes, the Model Reference System changes with it and no longer coincides with the Global Reference System. A given force or moment retains its magnitude when expressed in either system, but its X, Y, and Z components may differ. The Model Reference System facilitates interpretation relative to the body, whereas the Global Reference System enables results to be interpreted relative to the scene's fixed axes. Use the same reference system when comparing results.