Interacting with Augmented Floor Surfaces - Human Walking in Virtual Environments - page 373

Fig. 17.3 The step WIM interface of LaViola et al. introduced an interactive floor display for
navigating within a virtual environment via foot gestures performed with instrumented shoes [ 19 ]
17.3 Techniques and Technologies
Augmented floor surfaces that can respond to actions of the feet of persons moving on
them can, as envisioned here, be said to consist of interfaces comprising interactive
visual, audio, and/or tactile displays located on the walking surface together with
sensing technologies capable of capturing movements of the feet, contact or forces
between the feet and ground, or other movements of the body. Existing devices can
be distinguished according to the choices of sensing and display technologies that
they employ.
17.3.1 Indirect Optical Sensing
One sensing method that is frequently used to implement interactive floor displays
involves the inference of body position or movement from video capture in a re-
gion above the floor. This is the technique used in systems that have been com-
mercialized by several companies (e.g., Gesturetek and Reactrix). The disadvantage
of such an approach is that it normally provides no direct information about foot-
floor contact forces, contact onset, or contact area, and is thus unable to distinguish
between near-contact and the actual instant of contact between foot and ground.
Arguably, this distinction is vital for the convincing rendering of interactions with
virtual objects or controls, or for simulating highly contact-dependent interactions
with virtual materials [ 37 , 40 ].
Video-based sensing of the kinematics of walking interactions has been amainstay
in fields including gait analysis and biometrics [ 26 ], for example, in the identifica-
tion of pathological gait patterns with machine learning algorithms. Begg et al. [ 5 ],
among others, have used such algorithms to identify pathological gait using kine-
matic features acquired through optical motion capture, such as the minimum foot
clearance (a local minimum of the vertical distance between the shoe and ground
that occurs after toe off in the gait cycle).