Perceiving Absolute Distance in Augmented Reality Displays with Realistic and Non-realistic Shadows

Although distance perception to Augmented Reality (AR) objects has been studied for decades, little is known about absolute distance perception with the newest available AR displays. One significant distinction in categories of head-worn AR displays is whether they are optical see-through (OST) or video see-through (VST). These two types of devices have different methods of rendering that could affect the cues available for perceiving distance. Specifically, rendering cast shadows can be challenging, especially in OST displays that rely on additive light for rendering, and there may be alternative shadow shading methods that are equally as effective for conveying cues to depth. The current study tests absolute egocentric distance judgments to targets 3-6 meters away from an observer with two types of shadows, in two types of AR displays, the Hololens 2 (OST) and the Varjo XR-3 (VST). Shadows were realistic cast shadows or non-realistic shadows in the form of a stylized ring placed beneath the object. Participants verbally reported perceived distance to spherical virtual targets presented on or above the ground, viewed through the displays in a real world classroom. We found overall distance underestimation in both devices, but that estimations were more accurate with the Hololens 2 compared to the Varjo XR-3. There was little support for a difference in accuracy of estimations between shadow conditions or position on or above the ground (confirmed by a Bayesian analysis), suggesting that non-realistic shadows may be a good option for providing additional shading cues for depth in AR.