Many studies have found people can accurately judge distances in the real world while they underestimate distances in virtual reality (VR). This discrepancy negatively impacts some VR applications. Direct blind walking is a popular method of measuring distance judgments where participants view a target and then walk to it while blindfolded. To ensure that participants are comfortable with blindfolded walking, researchers often require participants to practice blind walking beforehand. We call this practice ”pre-experiment blind walking” (PEBW). Few studies report details about their PEBW procedure, and little research has been conducted on how PEBW might affect subsequent distance judgments. This between-participant study varied the amount of the PEBW and had participants perform distance judgments in VR. The results show that a longer PEBW causes less distance underestimation. This work demonstrates the importance of clearly reporting PEBW procedures and suggests that a consistent procedure may be necessary to reliably compare direct blind walking research studies.

Many HMD applications are improved when people perceive and act similarly in the virtual world as they would in an equivalent real environment. However, multiple studies show people underestimate egocentric distances in HMDs while being reasonably accurate in the real world. Some studies also show that brightness in the periphery may be one factor influencing these distance judgments. We built upon this previous work and examine if the brightness of the entire screen affects distance judgments. Using direct blind-walking, we compared a bright environment to an artificially darkened one with a between-subject experiment. The results of the experiment indicate that overall brightness has no significant effect on egocentric distance judgment. We discuss the implications of our findings in the context of previous work. Our findings may help designers of HMD software featuring dark environments (e.g., some entertainment applications).

No abstract available.

Computer graphics systems provide sophisticated means to render virtual 3D space to 2D display surfaces by applying planar geometric projections. In a realistic viewing condition the perspective applied for rendering should appropriately account for the viewer's location relative to the image. As a result, an observer would not be able to distinguish between a rendering of a virtual environment on a computer screen and a view “through” the screen at an identical real-world scene. Until now, little effort has been made to identify perspective projections which cause human observers to judge them to be realistic. In this article we analyze observers' awareness of perspective distortions of virtual scenes displayed on a computer screen. These distortions warp the virtual scene and make it differ significantly from how the scene would look in reality. We describe psychophysical experiments that explore the subject's ability to discriminate between different perspective projections and identify projections that most closely match an equivalent real scene. We found that the field of view used for perspective rendering should match the actual visual angle of the display to provide users with a realistic view. However, we found that slight changes of the field of view in the range of 10-20% for two classes of test environments did not cause a distorted mental image of the observed models.

The display units integrated in today's head-mounted displays (HMDs) provide only a limited field of view (FOV) to the virtual world. In order to present an undistorted view to the virtual environment (VE), the perspective projection used to render the VE has to be adjusted to the limitations caused by the HMD characteristics. In particular, the geometric field of view (GFOV), which defines the virtual aperture angle used for rendering of the 3D scene, is set up according to the display field of view (DFOV). A discrepancy between these two fields of view distorts the geometry of the VE in a way that either minifies or magnifies the imagery displayed to the user. It has been shown that this distortion has the potential to affect a user's perception of the virtual space, sense of presence, and performance on visual search tasks. In this paper, we analyze the user's perception of a VE displayed in a HMD, which is rendered with different GFOVs. We introduce a psychophysical calibration method to determine the HMD's actual field of view, which may vary from the nominal values specified by the manufacturer. Furthermore, we conducted two experiments to identify perspective projections for HMDs, which are identified as natural by subjects--even if these perspectives deviate from the perspectives that are inherently defined by the DFOV. In the first experiment, subjects had to adjust the GFOV for a rendered virtual laboratory such that their perception of the virtual replica matched the perception of the real laboratory, which they saw before the virtual one. In the second experiment, we displayed the same virtual laboratory, but restricted the viewing condition in the real world to simulate the limited viewing condition in a HMD environment. We found that subjects evaluate a GFOV as natural when it is larger than the actual DFOV of the HMD--in some cases up to 50 percent--even when subjects viewed the real space with a limited field of view.

The display units integrated in todays head-mounted displays (HMDs) provide only a limited field of view (FOV) to the virtual world. In order to present an undistorted view to the virtual environment (VE), the perspective projection used to render the VE has to be adjusted to the limitations caused by the HMD characteristics. In particular, the geometric field of view (GFOV), which defines the virtual aperture angle used for rendering of the 3D scene, is set up according to the display's field of view. A discrepancy between these two fields of view distorts the geometry of the VE in a way that either minifies or magnifies the imagery displayed to the user. Discrepancies between the geometric and physical FOV causes the imagery to be minified or magnified. This distortion has the potential to negatively or positively affect a user's perception of the virtual space, sense of presence, and performance on visual search tasks.