Biomedical Engineering Reference
In-Depth Information
view coincided with the lowest point of their physical vertical oscillatory motion).
In fact, the compellingness and amplitude of the perceived self-motion was not
significantly smaller than in a previous study where visual and inertial motion was
synchronized and not phase-shifted [
129
]. Moreover, for both horizontal and vertical
visual motions, perceived motion directions were almost completely dominated by
the visual, not the inertial motion. That is, while there was some sort of “visual
capture” of the perceived motion direction, the extent and convincingness of the
perceived self-motion was modulated by the amount of inertial acceleration.
Recently, Seno et al. [
106
] demonstrated that air flow provided by a fan positioned
in front of observers' face significantly enhanced visually induced forward linear
vection. Backward linear vection was not facilitated, however, suggesting that the
air flow needs to at least qualitatively match the direction of simulated self-motion,
similar to head wind.
In two recent studies, Ash et al. showed that vection is enhanced if participants'
active head movements are updated in the visual self-motion display, compared to
a condition where the identical previously recorded visual stimulus was replayed
while observers did not make any active head-movements [
5
,
6
]. This means that
vection was improved by consistent multisensory stimulation where sensory informa-
tion from own head-movements (vestibular and proprioceptive) matched visual self-
motion information on the VR display [
6
]. In a second study with similar setup, [
5
]
found that adding a deliberate display lag between the head and display motion mod-
estly impaired vection. This finding is highly important since in most VR applications,
end-to-end system lag is present, especially in cases of interactive, multisensory, real-
time VR simulations. Despite technical advancement, it is to be expected that this
limitation cannot be easily overcome in the near future.
In conclusion, there can often be substantial benefits in providing coherent self-
motion cues in multiple modalities, even if they can only be matched qualitatively.
Budget permitting, allowing for actual physical walking or full-scale motion or
motion cueing on 6DoF motion platforms is clearly desirable and might be nec-
essary for specific commercial applications like flight or driving simulation. When
budget, space, or personnel is more limited, however, substantial improvements can
already be gained by relatively moderate and affordable efforts, especially if consis-
tent multi-modal stimulation and higher-level influences are thoughtfully integrated.
Although they do not provide physically accurate simulation, simple means such
as including vibrations, jerks, spatialized audio, or providing a perceptual-cognitive
mercially available motion seats or gaming seats can provide considerable benefits
to self-motion perception and overall simulation effectiveness [
87
].
As we will discuss in our conceptual framework in Sect.
2.9
in more detail, it is
essential to align and tailor the simulation effort with the overarching goal: e.g., is
the ultimate goal physical correctness, perceptual effectiveness, or behavioral real-
ism? Or is there a stronger value put on user's overall enjoyment, engagement, and
immersion, as in the case of many entertainment applications, which represent a
considerable and increasing market share?
