Moving the grasping hand does not move
the grabbed rung or change the user’s vertical position. Instead,
the virtual hand remains in the original grasping position (Figure
1B) as long as the user keeps both buttons pressed and the user’s
physical hand remains within a bounding volume of 3.5 ft. x 2 ft.
x 2 ft. centered at the grasping point. This design nuance was
derived from pilot testing. Due to balance issues from marching
on one foot at a time, users were unable to maintain hand contact
with the virtual rung. Our bounding volume alleviates this issue,
but allows well-balanced users to climb with little arm motions.
To mimic placing a foot on a higher rung and then stepping up
off the ground, we use a marching technique. The user raises and
lowers his or her foot as if marching in place, however when the
user’s virtual sole comes in contact with the top of a virtual rung
while being lowered, our technique simulates the user stepping up
(Figure 1B). This is accomplished by changing the mapping
between the physical tracking space and the virtual environment
to raise the user’s virtual body up.
Instead of using a discrete step up, we allow the user’s physical
foot position relative to the physical ground to define a dynamic
and continuous vertical movement. If the user’s sole raises above
the rung being stepped on, this vertical movement ceases. Once
the user’s foot comes in contact with the ground, it also ceases.
Due to the lack of force feedback when stepping on the virtual
rung, we display the user’s virtual feet 10 inches in front of their
physically tracked positions to provide the user visual feedback of
contacting the rung. This was another design nuance discovered
during pilot testing when users could not keep their feet in contact
with the ladder and see where their hands were positioned.