Interacting with Augmented Floor Surfaces - Human Walking in Virtual Environments - page 381

Fig. 17.11 Left still image of user interacting with the simulated frozen pond. Right a user engaged
with a simulation of water in a shallow pool
17.4.2 Virtual Walking on Natural Materials
Several techniques have been developed to enable users to interact on foot with
simulated natural ground surfaces, such as soil or ice, using the floor surface described
above. For a review of this and related work, see Chap. 12 of this topic. Position and
force estimates from in-floor force sensors are used to synthesize plausible auditory
and vibrotactile feedback in response. Sensations accompanying walking on natural
ground surfaces in real world environments (sand in the desert, or snow in winter) are
multimodal and can be highly evocative of the settings in which they occur [ 38 ]. By
reproducing these sensations through auditory, visual, and vibrotactile channels, it is
possible to recreate highly evocative scenarios of walking on virtual ground surfaces.
Figure 17.11 illustrates two interactive scenarios that were realized based on the
interface and interaction techniques presented above. The first represents a virtual
frozen pond demonstration that users may walk on, producing patterns of surface
cracks that are rendered and displayed via audio, visual, and vibrotactile channels
(Fig. 17.11 ). A second simulation uses the same feedback modalities to realize the
experience of walking on a shallow pool of water. For further discussion of the
multimodal rendering algorithms used in these simulations, see Chap. 12 .
17.4.3 Floor Touch-Surface Interaction Techniques
The floor interface described above was used to implement virtual floor-based touch
interfaces, using either foot based gestures or standard UI widgets controlled with
the feet (Fig. 17.12 ). Input is derived from a multi-touch-screen metaphor relying
on a set of interaction points, which are given by the contact centroid locations x c
associated with the largest forces. Force thresholds assigned to a control are used
to determine selection. The controls can also provide positive tactile feedback via