Most head-mounted displays (HMDs) suffer from substantial optical distortion, and vendor-supplied specifications for fieldof-view often are at variance with reality. Unless corrected, such displays do not present perspective-related visual cues in a geometrically correct manner. Distorted geometry has the potential to affect applications of HMDs, which depend on precise spatial perception. This article provides empirical evidence for the degree to which common geometric distortions affect one type of spatial judgment in virtual environments. We show that minification or magnification in the HMD that would occur from misstated HMD field of view causes significant changes in distance judgments. Incorrectly calibrated pitch and pincushion distortion, however, do not cause statistically significant changes in distance judgments for the degree of distortions examined. While the means for determining the optical distortion of display systems are well known, they are often not used in non-seethrough HMDs due to problems in measuring and correcting for distortion. As a result, we also provide practical guidelines for creating geometrically calibrated systems.

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Most head-mounted displays (HMDs) suffer from substantial optical distortion, and vendor-supplied specifications for field-of-view often are at variance with reality. Such displays do not present perspective-related visual cues in a geometrically correct manner, which has the potential to affect applications of HMDs which depend on precise spatial perception. This paper provides empirical evidence for the degree to which these resulting distortions affect one type of spatial judgment in virtual environments. We show that minification in the HMD that would occur from an overstated HMD field of view results in a significant change in distance judgments. Incorrectly calibrated pitch and pincushion distortion, however, did not cause statistically significant changes in distance judgments for the degree of distortions examined. While the means for determining the optical distortion of display systems are well known, they are often not used in non-see-through HMDs due to problems in measuring and correcting for distortion. As a result, we also provide practical guidelines for creating geometrically calibrated systems.

Numerous studies report that people underestimate egocentric distances in Head-Mounted Display (HMD) virtual environments compared to real environments as measured by direct blind walking. Geometric minification, or rendering graphics with a larger field of view than the display's field of view, has been shown to eliminate this underestimation in a virtual hallway environment [Kuhl et al. 2006[Kuhl et al. , 2009. This study demonstrates that minification affects blind walking in a sparse classroom and does not influence verbal reports of distance. Since verbal reports of distance have been reported to be compressed in real environments, we speculate that minification in an HMD replicates peoples' real-world blind walking and verbal report distance judgments. We also demonstrate a new method for quantifying any unintentional miscalibration in our experiments. This process involves using the HMD in an augmented reality configuration and having each participant indicate where the targets and horizon appeared after each experiment. More work is necessary to understand how and why minification changes verbal-and walking-based egocentric distance judgments differently.

Distances in immersive virtual environments (VEs) have been commonly reported as being spatially compressed while the same judgments are performed accurately in real space. Previous research has been unable to determine the cause of this spatial compression in VEs. The work reported here seeks to improve spatial judgments in VEs by manipulating the computer graphics in a way that biases distance judgments in a controlled manner, but is unnoticed by VE users. We show that shrinking the displayed image and appropriately rendering the scene to fill in the space resulting from shrinking the image ("minification") causes people to make more accurate distance judgments than they do with normally rendered graphics. Possible explanations for this effect include changes to the visual angle of declination from horizon to targets and changes in familiar size.