Visual Transitions around Tabletops in Mixed Reality: Study on a Visual Acquisition Task between Vertical Virtual Displays and Horizontal Tabletops
See-through Head-Mounted Displays (HMDs) offer interesting opportunities to augment the interaction space around screens, especially around horizontal tabletops. In such context, HMDs can display surrounding vertical virtual windows to complement the tabletop content with data displayed in close vicinity. However, the effects of such combination on the visual acquisition of targets in the resulting combined display space have scarcely been explored. In this paper we conduct a study to explore visual acquisitions in such contexts, with a specific focus on the analysis of visual transitions between the horizontal tabletop display and the vertical virtual displays (in front and on the side of the tabletop). To further study the possible visual perception of the tabletop content out of the HMD and its impact on visual interaction, we distinguished two solutions for displaying information on the horizontal tabletop: using the see-through HMD to display virtual content over the tabletop surface (virtual overlay), i.e. the content is only visible inside the HMD’s FoV, or using the tabletop itself (tabletop screen). 12 participants performed visual acquisition tasks involving the horizontal and vertical displays. We measured the time to perform the task, the head movements, the portions of the displays visible in the HMD’s field of view, the physical fatigue and the user’s preference. Our results show that it is faster to acquire virtual targets in the front display than on the side. Results reveal that the use of the virtual overlay on the tabletop slows down the visual acquisition compared to the use of the tabletop screen, showing that users exploit the visual perception of the tabletop content on the peripheral visual space. We were also able to quantify when and to which extent targets on the tabletop can be acquired without being visible within the HMD's field of view when using the tabletop screen, i.e. by looking under the HMD. These results lead to design recommendations for more efficient, comfortable and integrated interfaces combining tabletop and surrounding vertical virtual displays.