Model FixedArrow defines an arrow that is shown
at the location of its frame_a.
The direction of the arrow specified with vector n
is with respect to frame_a, i.e., the local frame to which the
arrow component is attached. The direction, length and color of the
arrow can vary dynamically by providing appropriate expressions in
the input fields of the parameter menu.
The quantity
parameter defines what the vector
represents, allowing tools to scale e.g. forces and torques
differently in a consistent way. For the default value
RelativePosition the obvious scaling is 1 and
the relative position is shown as is.