How do I determine which direction is Longitudinal and which is Transverse?
This is done on the Moment Envelope Generation page, which can be accessed as shown below:
The pane to the right allows you to specify the direction of the longitudinal axis. Default is along the global X direction, but you can choose the global Z or specify a custom direction if desired:
Please note, to specify a custom direction you must provide the start/end X and Z coordinates for a line in the desired direction.
The transverse direction is, by definition, perpendicular to the longitudinal axis.