Virtual humans (VHs) in augmented reality (AR) can provide users an illusory sense of being together in the real space. However, such an illusion can easily break when the augmented VH conflicts (or is overlaid) with the real objects. Recent spatial understanding technology is starting to make physically plausible VHs in response to collisions, but there are still limitations (e.g., resolution, accuracy) and inevitable conflict situations (e.g., unexpected passer-by), especially in daily life. Moreover, depending on the situation, VH’s plausible behavior to avoid collision may rather interfere with the original interaction with the users. In this paper, we investigate three such situations: (1) when VH appears in a room through a closed door, (2) when the VH’s body overlaps with static real objects, and (3) when a real moving object passes through the VH. While we considered (2) as an avoidable situation where physically plausible behaviors of VHs might be required, (1) and (3) were considered as inevitable situations (e.g., VH appearing out of nowhere, or passer-by cannot be aware of a virtual being), and we may not present VH’s plausible behaviors, so alternatives might be required. Thus, for each of these notable situations in AR, we tested different visual effects as presentation methods for physical conflicts between a VH and real objects. Our findings indicate that visual effects improve VH’s social/co-presence and physicality depending on the situations and effect types as well as influence users’ attention/social behaviors. We discuss the implications of our findings and future research directions.

In this paper, we applied the concept of diminished reality to remove content-irrelevant pedestrian (i.e., real object) in the context of handheld augmented reality (AR). We prepared three view conditions: in Transparent (TP) condition, we removed the pedestrian entirely; in Semi-transparent (STP) condition, the pedestrian became semi-transparent; lastly, in Default (DF) condition, the pedestrian appeared as is. We conducted a user study to compare the effects of the three conditions on users’ engagement and perception of a virtual pet in the AR content. Our findings revealed that users felt less distracted to the AR content in TP and STP conditions, compared to the DF condition. Furthermore, users felt the virtual pet as more life-like, its behavior more plausible, and felt a higher spatial presence in the real environment, in the TP condition.

Virtual reality (VR) offers a compelling and immersive experience; however, cybersickness (or VR sickness) stands as a significant obstacle to its widespread adoption. When a user experiences cybersickness, one’s physical condition deteriorates with various symptoms, often accompanied by an increased and destabilized heart rate and even altered perception of one’s state. In this paper, we propose to provide “False but Stable Heart rate (FSH)” feedback through auditory and vibrotactile stimulation to reversely induce a stably perceived heart rate and, thereby, alleviate cybersickness while navigating a sickness-inducing VR content. The validation of the human experiment confirmed the intended effect in a statistically significant way. Furthermore, it was found that the lesser compatible FSH feedback had a more substantial sickness reduction effect but distracted the user with the reduced immersive experience. The compatible FSH feedback still showed moderate sickness reduction with the maintained sense of presence and immersion.

Cybersickness (CS) is a serious usability problem in virtual reality (VR). Postural instability theory has emerged as one major hypothesis for the cause of CS. Based on such a hypothesis, we present two experiments to observe the trends in users’ trained balance ability with respect to their susceptibilities to CS. The first experiment (as a preliminary study) evaluated the effects of 2-week balance training under three different operational conditions: training in VR (VRT), training in non-immersive media with a 2D projection display (2DT), and VR exposure without any training (VRO; Baseline). The effect toward CS was tested not only in the training space but also in a different VR content to observe for any transfer effect. As results clearly indicated that the non-VR 2DT was ineffective in gaining any significant tolerance to CS, we conducted a follow-up second experiment with 1-week balance training, focusing on comparing only the VRT and VRO conditions. Overall, the experimental findings have shown, aside from the obvious improvement in balance performance itself, that accompanying balance training had the stronger effect of increasing tolerance to CS than mere exposure to VR. Furthermore, the tolerance to CS developed through VR balance training exhibited a transfer effect, that is, with reduced levels of CS in another VR content (not used during the training sessions).

Augmented reality (AR) scenes often inadvertently contain real world objects that are not relevant to the main AR content, such as arbitrary passersby on the street. We refer to these real-world objects as content-irrelevant real objects (CIROs). CIROs may distract users from focusing on the AR content and bring about perceptual issues (e.g., depth distortion or physicality conflict). In a prior work, we carried out a comparative experiment investigating the effects on user perception of the AR content by the degree of the visual diminishment of such a CIRO. Our findings revealed that the diminished representation had positive impacts on human perception, such as reducing the distraction and increasing the presence of the AR objects in the real environment. However, in that work, the ground truth test was staged with perfect and artifact-free diminishment. In this work, we applied an actual real-time object diminishment algorithm on the handheld AR platform, which cannot be completely artifact-free in practice, and evaluated its performance both objectively and subjectively. We found that the imperfect diminishment and visual artifacts can negatively affect the subjective user experience.