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Accurate perception of the size of objects in computer-generated imagery is important for a growing number of applications that rely on absolute scale, such as medical visualization and architecture. Addressing this problem requires both the development of effective evaluation methods and an understanding of what visual information might contribute to differences between virtual displays and the real world. In the current study, we use 2 affordance judgments--perceived graspability of an object or reaching through an aperture--to compare size perception in high-fidelity graphical models presented on a large screen display to the real world. Our goals were to establish the use of perceived affordances within spaces near to the observer for evaluating computer graphics and to assess whether the graphical displays were perceived similarly to the real world. We varied the nature of the affordance task and whether or not the display enabled stereo presentation. We found that judgments of grasping and reaching through can be made effectively with screen-based displays. The affordance judgments revealed that sizes were perceived as smaller than in the real world. However, this difference was reduced when stereo viewing was enabled or when the virtual display was viewed before the real world., ((c) 2015 APA, all rights reserved).)

For low vision navigation, misperceiving the locations of hazards can have serious consequences. Potential sources of such misperceptions are hazards that are not visually associated with the ground plane, thus, depriving the viewer of important perspective cues for egocentric distance. In Experiment 1, we assessed absolute distance and size judgments to targets on stands under degraded vision conditions. Normally sighted observers wore blur goggles that severely reduced acuity and contrast, and viewed targets placed on either detectable or undetectable stands. Participants in the detectable stand condition demonstrated accurate distance judgments, whereas participants in the undetectable stand condition overestimated target distances. Similarly, the perceived size of targets in the undetectable stand condition was judged to be significantly larger than in the detectable stand condition, suggesting a perceptual coupling of size and distance in conditions of degraded vision. In Experiment 2, we investigated size and implied distance perception of targets elevated above a visible horizon for individuals in an induced state of degraded vision. When participants' size judgments are inserted into the size-distance invariance hypothesis (SDIH) formula, distance to above-horizon objects increased compared to those below the horizon. Together, our results emphasize the importance of salient visible ground-contact information for accurate distance perception. The absence of this ground-contact information could be the source of perceptual errors leading to potential hazards for low vision individuals with severely degraded acuity and contrast sensitivity.

In 4 experiments, the authors varied the extent and nature of participant movement in a virtual environment to examine the influence of action on estimates of geographical slant. Previous studies showed that people consciously overestimate hill slant but can still accurately guide an action toward the hill (D. R. Proffitt, M. Bhalla, R. Gossweiler, & J. Midgett, 1995). Related studies suggest that one's potential to act may influence perception of slant and that distinct representations may independently inform perceptual and motoric responses. The authors found that in all conditions, perceptual judgments were overestimated and motoric adjustments were more accurate. The virtual environment allowed manipulation of the effort required to walk up simulated hills. Walking with the effort appropriate to the visual slant led to increased perceptual overestimation of slant compared with active walking with the effort appropriate to level ground, while visually guided actions remained accurate., ((c) 2004 APA, all rights reserved)

Virtual environments (VEs) presented via head-mounted displays are typically perceived as smaller in scale than intended. Visual–motor experience in VEs can reduce this underestimation of distance, though the mechanisms underlying this improved accuracy of distance estimates are unknown. To address this question, we created a mismatch between biomechanical and visual indicators of self-movement within the VE, and assessed the effect on distance and size judgments. Our results suggest that visual–motor feedback influences subsequent distance judgments by recalibrating perceptual–motor relationships, but we found no evidence that perceived size, which was substantially underestimated, changed as a function of this feedback. In contrast to recent studies that suggest that feedback in VEs causes a broad rescaling of virtual space, our results are consistent with a visual–motor recalibration account for much of the improvement in distance judgments following VE experience. [ABSTRACT FROM AUTHOR]