Biomedical Engineering Reference
In-Depth Information
12.3.5.4 Augmenting Footsteps with Simulated Multimodal Feedback
The enhancement of walking sensations over virtual grounds is not necessarily lim-
ited to immersive virtual reality setups. Some applications should be able to run
in desktop mode, i.e. when the user is seated and is using a basic computer. This
includes training applications that need to be massively deployed, or video games.
To give the sensation of walking, video games use auditory feedback intensively and
footstep sounds to simulate steps. Visual information can also be used to enhance
the sensation of walking.
In this desktop VR context, Terziman et al. [
98
] introduced a set of cues to augment
virtual footsteps with artificial (exaggerated) multimodal feedback, called “King-
Kong Effects”. These sensory cues are inspired by special effects in movies in which
the incoming of a gigantic creature is suggested by adding visual vibrations/pulses to
the camera at each of its steps. Visual, tactile and acoustic signals artificially enhance
each footstep detected (or simulated) during the virtual walk of the user sitting in front
of the computer. The system leverages the tiles presented in Sect.
12.3.4.2
located
under the user's feet, for vibrotactile rendering of foot-floor impact, in addition to
the visual camera vibrations and acoustic rendering of footsteps. The authors studied
the use of different kinds of feedback cues based on vertical or lateral oscillations,
physical or metaphorical patterns, and one or two peaks for heal-toe contacts simula-
tion. They showed that for a seated user, the sensation of walking is increased when
the different modalities are taken together, and strongly recommend the use of such
a multimodal simulation for an improved user immersion.
12.3.5.5 Pseudo-Haptic Rendering of Virtual Grounds
Pseudo-haptic feedback leverages the crossmodal integration of visual and kines-
thetic cues giving rise to an illusion of force feedback [
58
]. Pseudo-haptic feedback
was initially obtained by combining the use of a passive input device with visual feed-
back, simulating haptic properties such as stiffness or friction [
59
]. For example, to
simulate the friction occurring when inserting an object inside a narrow passage,
researchers proposed to artificially reduce the speed of the manipulated object dur-
ing the insertion. Assuming that the object is manipulated with an isometric input
device, the user will have to increase his pressure on the device to make the object
advance inside the passage. The coupling between the slowing down of the object on
the screen and the increasing reaction force coming from the device gives the user
the illusion of a force feedback as if a friction force was generated.
Marchal et al. [
65
] brought the concept of pseudo-hatic feedback to walking
interaction in immersive VR, inspired by the use of virtual camera motions [
60
,
97
]
to improve the sensation of walking in a virtual environment. The modification of
the subjective visual feedback of the user, combined to the real kinesthetic cues of
the user walking on the real ground surface, gives rise to the illusion of walking on
uneven terrain. The authors base their study on the modification of the user viewpoint
by changing height, speed and orientation of the virtual subjective camera according
