# The Effects of Augmented Reality Interaction Techniques on Egocentric Distance Estimation Accuracy
## 4 Discussion  
This study investigated the effects of two interaction techniques, direct pointing and indirect cursor, when a stereoscopic target was displayed in a projection-based display. The results revealed evident effects of the interaction technique, the egocentric distance, and the index of difficulty on the accuracy of interaction performance. Estimation of egocentric distance was less accurate with the direct pointing technique (90%) than with the indirect cursor technique (95%). This finding supports our experimental hypothesis that egocentric distance estimation is more accurate with the indirect cursor technique than with the direct pointing one. A plausible explanation is the visual conflicts that may occur when a virtual object is selected with the direct pointing technique [63]. In particular, when a participant tries to point a pointing stick at a virtual object in a stereoscopic environment, either the virtual object or the pointing stick will appear blurred. On the other hand, with the indirect cursor, since both the virtual targets and the virtual cursor were displayed stereoscopically in this study, the visual conflicts might have been reduced [40]. Another possible explanation might be related to an occlusion cue that occurred in the indirect cursor condition. When the virtual cursor passed through the virtual target, the cursor would occlude the spherical virtual target. Thus, with this cue,  
Figure 5: Results of task completion time for direct pointing and indirect cursor interaction techniques with respect to egocentric distance (**A**) and index of difficulty (**B**). The error bar represents standard error of mean. Figure 6: Results of throughput for direct pointing and indirect cursor interaction techniques with respect to egocentric distance (**A**) and index of difficulty (**B**). The error bar represents standard error of mean. the participant might be aware that the cursor was passing behind the target. Although no visual feedback (e.g., color change) was provided when the cursor touched the target, the presence of the hand cursor could be a visual cue leading to the higher accuracy than that of the direct pointing technique. In addition, since the size of the virtual cursor was scaled approximately to the width of each target, as the cursor moved toward the target, the cursor was comparable until it was almost the same size as the target, which could indicate that they were at the same depth. In other words, when the hand cursor appeared smaller than the target, the size difference indicated that the cursor was farther from the target. Therefore, it was possible that the participants' judgment benefited from this relative size cue. This study also found that underestimations consistently occurred at each egocentric distance in the indirect cursor condition. On average, participants underestimated target positions by 4, 5, and 7 cm when the targets were displayed at distances of 90 cm, 120 cm, and 150 cm, respectively. This phenomenon was observed in other studies. A comprehensive review by [PERSON] and [PERSON] [32] on studies of egocentric distance perspective in VR mostly showed underestimations. One may expect that this result indicates compression of the intended size of the virtual space [34; 59]. Some researchers have claimed that such compression might be ascribed to measurement methods and technical issues [35], the low quality of graphics [64], experience in VR [65], and distance cues [66]. However, no consensus has been reached on the causes. In contrast to the indirect cursor technique, in this study, egocentric distance estimation was overestimated with the direct pointing technique in all target distance conditions. On average, distances were overestimated by 6 to 8 cm for all tested target distances (90 cm, 120 cm, and 150 cm from the participant). These results are in line with previous studies showing that the accuracy of egocentric distance estimations in stereoscopic displays up to a distance of 1.5 m was less precise and overestimated [11; 13; 67].