The change in this Body's vertical position from the previous game update.
This value is set during the
postUpdate phase and takes into account the
deltaMax and final position of the Body.
Because this value is not calculated until
postUpdate, you must listen for it
during a Scene
RENDER event, and not in
update, as it will
not be calculated by that point. If you do use these values in
will represent the delta from the previous game frame.
The final delta y value.