Many authors report that binocular vision plays an important role in the evaluation of the distance to scenery objects. Furthermore, it was observed that narrow (<20°) angular visual observation field, called field of view, causes underestimation of distances to objects in natural scenes. In a series of experiments we studied if distances were underestimated for larger fields of views (60°, 90° and 120°) and if binocular vision could correct distance estimation. We have also studied distance estimation in virtual environments in the same observation conditions as it is known that it may be poorer because of the lack or bias of visual stimuli. Observers had to estimate proximal distances in real and virtual (large fields of view head mounted display and power wall) scenes of a car interior. We have found that there is a strong underestimation of distances in observing proximal objects (≤50cm) in a reduced field of view for both real and virtual scenes and more the field of view is reduced, more observers underestimate distances. Furthermore underestimation is stronger in virtual environments for the same objects than in real ones. We have also compared distance estimations between monocular and binocular observation conditions and found no significant differences for all fields of view. Our results show that binocular vision is not allowing better distance estimation than monocular vision. These results suggest an unexpectedly weak effect of binocular vision on the observation of distances of proximal objects in multi-cue environments.
The perceptual effects of changes of texture luminance either between the eyes or over time have been studied in several experiments and have led to a better comprehension of phenomenons such as sieve effect, binocular and monocular lustre and rivaldepth.
In this paper, we propose an ecological model of glittering texture and analyze glitter perception in terms of variations of texture luminance and animation frequency, in dynamic illumination conditions. Our approach is based on randomly oriented mirrors that are computed according to the specular term of Phong's image rendering formula. The sparkling effect is thus correlated to the relative movements of the resulting textured object, the light array and the observer's point of view.
The perceptual effect obtained with this model depends on several parameters: mirrors' density, the Phong specular exponent and the statistical properties of the mirrors' normal vectors. The ability to independently set these properties offers a way to explore a characterization space of glitter. A rating procedure provided a first approximation of the numerical values that lead to the best feeling of typical sparkling surfaces such as metallic paint, granite or sea shore.
Different stereoscopic effects, base don 100 percent binocular luminance contrast have been described previously: the 'sieve' effect, the 'binocular lustre' effect, the 'floating' effect and the rivaldepth' effect. By mean of a dichoptic set-up, we have measured the detection thresholds for these different effects in function of binocular luminance contrast. Psychometric data have ben recorded using a Yes-No paradigm, a spatial 2AFC paradigm and a temporal 2AFC paradigm. Our results show that even for small contrast all these stereoscopic effects are perceived. We have noticed an increase of the detection thresholds in the following order: 'sieve', 'binocular lustre', 'rivaldepth' and 'floating' effect. Two groups have been distinguished.
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