Impact of visual and experiential realism on distance perception in VR using a custom video see-through system

Immersive virtual reality (VR) technology has the potential to play an important role in the conceptual design process in architecture, if we can ensure that sketch-like structures are able to afford an accurate egocentric appreciation of the scale of the interior space of a preliminary building model. Historically, it has been found that people tend to perceive egocentric distances in head-mounted display (HMD) based virtual environments as being shorter than equivalent distances in the real world. Previous research has shown that in such cases, reducing the quality of the computer graphics does not make the situation significantly worse. However, other research has found that breaking the illusion of reality in a compellingly photorealistic VR experience can have a significant negative impact on distance perception accuracy. In this paper, we investigate the impact of "graphical realism" on distance perception accuracy in VR from a novel perspective. Rather than starting with a virtual 3D model and varying its surface texture, we start with a live view of the real world, presented through a custom-designed video/optical-see-through HMD, and apply image processing to the video stream to remove details. This approach offers the potential to explore the relationship between visual and experiential realism in a more nuanced manner than has previously been done. In a within-subjects experiment across three different real-world hallway environments, we asked people to perform blind walking to make distance estimates under three different viewing conditions: real-world view through the HMD; closely registered camera views presented via the HMD; and Sobel-filtered versions of the camera views, resulting a sketch-like (NPR) appearance. We found: 1) significant amounts of distance underestimation in all three conditions, most likely due to the heavy backpack computer that participants wore to power the HMD and cameras/graphics; 2) a small but statistically significant difference in the amount of underestimation between the real world and camera/NPR viewing conditions, but no significant difference between the camera and NPR conditions. There was no significant difference between participants' ratings of visual and experiential realism in the real world and camera conditions, but in the NPR condition participants' ratings of experiential realism were significantly higher than their ratings of visual realism. These results confirm the notion that experiential realism is only partially dependent on visual realism, and that degradation of visual realism, independently of experiential realism, does not significantly impact distance perception accuracy in VR.