ABOVE & BELOW: Investigating Ceiling and Floor for Augmented Reality Content Placement

Displaying content above on the ceiling and below on the floor was already explored in several use cases, such as a visit to public spaces (e.g., museum) [25, 29], indoor guidance [1, 15, 25], outdoor guidance [2,38], office work [4,37], smart living spaces [5,11,19,28], gaming [8], industrial applications [21], and for awareness and ambient displays [9, 13, 14, 17, 22, 33, 34]. To display content in these areas, monitor systems, stationary and wearable projectors, and HMDs were mainly used in previous works. We can group these works into UbiComp solutions and personal augmentation considering the used display technologies (see Tab. A1). The majority of related work can be classified as UbiComp solutions using two display technologies: (1) Monitor systems with a single or multiple displays on the ceiling [33, 34] or on the floor [15,28], as well as low-resolution displays consisting of individual LED units [36]; (2) Projector setups, either with rear projection on the ceiling [37] and floor [3] to avoid shadowing, or front projection on the ceiling [19] and floor [8]. As both display technologies are stationary and mostly directly embedded into the environment, it is possible to optimize the presentation of the virtual content to the environment. Furthermore, by using additional hardware (e.g., Kinect), it is possible to track further information which can be used for, e.g., foot or touch interaction [3, 5, 28] or position, posture, or gesture tracking [8–10, 17, 19, 36]. However, in these works, the augmentation is limited to the predefined local area and, through the global nature of such installations, presented content is always visible to all persons in this environment. Furthermore, areas of displays or the projection can be occluded by persons or objects. A smaller group of the related literature could be classified as a personal augmentation using the following two display technologies: (1) Pico-projectors worn, e.g., in a handbag [14], around the neck [26], or at the waist of the user [7], as well as other mobile projectors, such as a projector-quadcopter [12]; (2) Head-mounted displays [25, 31]. These technologies allow a mobile and dynamic augmentation of the environment since they are directly bound to the user by, e.g., wearing such devices. In general, body-bound devices allow the presentation of additional virtual information in any given environment, which is also visible in the number of use cases focused on navigational tasks (e.g., [24, 31, 35]). However, optimizing the display of these devices for the real-world environment is more challenging than using stationary setups embedded in the environment. Wearable projectors allow to augment a specific area on either the ceiling or the floor and are limited to the displayable area. In comparison, despite the low resolution of current OST HMDs, they enable to augment both the ceiling and the floor and other areas of the environment simultaneously while not being limited to the FoV of these devices. While Renner and Pfeiffer [25] and Thi Minh Tran and Parker [31] supported navigation task with the floor visualization, to the best of our knowledge, no previous studies have systematically investigated content placement both on the ceiling and the floor using AR HMDs. While investigating foot-tap interaction with an interface displayed on the floor, Müller et al. [18] found that this kind of interface should be used for short-term and fine-grained interactions. Renner and Pfeiffer [25] showed that interfaces requiring the user to permanently look at the floor for the navigation task are not optimal considering the ergonomics. However, while comparing map locations for a simulated AR pedestrian navigation interface in a fully immersive virtual environment, Thi Minh Tran and Parker [31] found that participants prefer the display location on the floor in front of them than on their hands or as a floating display. In their study, Reiner et al. [24] compared displaying a 2D map in front of the user and a topographic layout of the terrain in the upper visual field in a route confirmation task. While simulating the task in a fully immersive virtual environment, they found that participants with prior virtual reality experience were more accurate during the task with the presentation in the upper visual field.