Version: Blender 2.80
This is to address an animation issue regarding objects that is parented
to other objects. When two objects are parented to each other and the
parent object is rotated none of the available orientations allow a
user to translate a single axis. So if the user wanted to animate an
object on the x-axis they couldn't just pull the x-axis on the viewport
without affecting possibly the y and/or z-axis.
I resolved this issue by creating an orientation called axial which
maintains the axis orientation for an object that is parented to another
object. So when the parent object is rotated the child object can still
move along single axes properly. This was done by computing the final
orientatin of an object but ignoring the effects of rotation allowing
for controlled movement transformation. When the child is moved or
rotated the movement transformation gizmo remains stable, it only
rotates when the parent object gets rotated.