Extended Reality (XR) is uniquely capable of spatial and embodied simulations for various modes of worlds, beings, and relations, which makes it a medium especially well suited to exploring, realizing, and advancing posthuman/more-than-human HCI agendas. However, the three major domains of HCI research on XR—space, body, and interaction—have largely been shaped by anthropocentric design assumptions that prioritize perceptual fidelity, human-like representation, and instrumental control. This paper argues for a critical reorientation beyond these norms by shifting the direction for the domains: the design of XR environments as speculative worlding; embodiments as distributed decentering; and enactments as entangled becoming. It further recognizes XR and posthuman/more-than-human HCI to be mutually enabling, and proposes a co-constitutive framework where they can both evolve as the three domains continuously shape one another. Its contribution is a conceptual provocation that provides a diagnostic vocabulary and schema to reinvent XR as a site for cultivating speculative, inclusive, and transformative futures through HCI research.

Augmented Reality (AR) is regarded as an innovative storytelling medium that presents novel experiences by layering a virtual narrative space over a real 3D space. However, understanding of how the virtual narrative space and the real space are connected with one another in the design of augmented narrative spaces has been limited. For this, we conducted a systematic literature review of 64 articles featuring AR storytelling applications and systems in HCI, AR, and MR research. We investigated how virtual narrative spaces have been paired, functionalized, placed, and registered in relation to the real spaces they target. Based on these connections, we identified eight dominant types of augmented narrative spaces that are primarily categorized by whether they virtually narrativize reality or realize the virtual narrative. We discuss our findings to propose design recommendations on how virtual-real connections can be incorporated into a more structured approach to AR storytelling.

We propose Object Cluster Registration (OCR) using Geometric Spatial Affordance Graph (GSAG) to support user interaction with multiple objects in a shared space generated from two dissimilar rooms. Previous research on generating a shared virtual space from dissimilar real spaces has only reflected the information of individual objects and aimed at maximizing the area of the shared space. This led to limited interactions relying on the singular affordances of objects, neglecting to consider the usability and effectiveness of the generated shared spaces. The proposed OCR with GSAG, which considers the relationship between objects based on facing formation, extracts optimal object cluster pairs to align dissimilar rooms in generating shared virtual spaces. In an evaluation study involving 100 multi-cluster space pairs, applying OCR using GSAG showed greater effectiveness in preserving object correlations compared to cases where OCR was not used. Furthermore, the size of the shared space did not significantly differ between the two methods. This suggests that factoring in the relationship between objects does not compromise the objective of maximizing the shared virtual space. The proposed method is expected to serve as a foundation for generating shared virtual spaces that are more user-oriented and efficient by facilitating a wider range of collaborative activities for remote users in dissimilar real spaces with varied configurations.

We report on a qualitative study in which 22 participants created Augmented Reality (AR) stories for outdoor cultural heritage sites. As storytelling is a crucial strategy for AR content aimed at providing meaningful experiences, the emphasis has been on what storytelling does, rather than how it is done, the end user’s needs prioritized over the author’s. To address this imbalance, we identify how recurring patterns in the spatial trajectories and narrative compositions of AR stories for cultural heritage sites are linked to the author’s intent and creative process: While authors tend to bind story arcs tightly to confined trajectories for narrative delivery, the need for spatial exploration results in thematic content mapped loosely onto encompassing trajectories. Based on our analysis, we present design recommendations for site-specific AR storytelling tools that can support authors in delivering their intent while leveraging the placeness of cultural heritage sites as a creative resource.

A critical yet unresolved challenge in designing space-adaptive narratives for Augmented Reality (AR) is to provide consistently immersive user experiences anywhere, regardless of physical features specific to a space. For this, we present a comprehensive analysis on a series of user studies investigating how the size, density, and layout of real indoor spaces affect users playing Fragments, a space-adaptive AR detective game. Based on the studies, we assert that moderate levels of traversability and visual complexity afforded in counteracting combinations of size and complexity are beneficial for narrative experience. To confirm our argument, we combined the experimental data of the studies (n=112) to compare how five different spatial complexity conditions impact narrative experience when applied to contrasting room sizes. Results show that whereas factors of narrative experience are rated significantly higher in relatively simple settings for a small space, they are less affected by complexity in a large space. Ultimately, we establish guidelines on the design and placement of space-adaptive augmentations in location-independent AR narratives to compensate for the lack or excess of affordances in various real spaces and enhance user experiences therein.

Despite the importance of avatar representation on user experience for Mixed Reality (MR) remote collaboration involving various device environments and large amounts of task-related information, studies on how controlling visual parameters for avatars can benefit users in such situations have been scarce. Thus, we conducted a user study comparing the effects of three avatars with different transparency levels (Nontransparent, Semi-transparent, and Near-transparent) on social presence for users in Augmented Reality (AR) and Virtual Reality (VR) during task-centric MR remote collaboration. Results show that avatars with a strong visual presence are not required in situations where accomplishing the collaborative task is prioritized over social interaction. However, AR users preferred more vivid avatars than VR users. Based on our findings, we suggest guidelines on how different levels of avatar transparency should be applied based on the context of the task and device type for MR remote collaboration.

This paper evaluates factors of social presence during a dynamic remote collaboration task in a technologically asymmetric Mixed Reality (MR) setting for two spatial layouts. While active movement during MR remote collaboration is afforded by how the shared 3D space is mediated and configured, studies investigating the impact of these conditions on user experience have been scarce. In a between-group study $(\mathrm{n}=48)$, a host user in Augmented Reality (AR) and a remote user in Virtual Reality (VR), both wearing Head Mounted Displays (HMDs), simultaneously moved around the shared space to find and assemble parts of a Mars exploration rover together, one group in a Peripheral layout and the other in a Scattered layout with disparate levels of spatial affordance. Results show that while VR facilitates higher co-presence and spatial presence than AR through HMDs, the Peripheral layout enables users to pay more attention to one another than the Scattered. We analyze the results and derive implications aimed at bridging the AR-VR gap in social presence for dynamic MR remote collaboration through the adaptive placement of virtual content in shared spaces.

This paper investigates how the size of virtual space and objects within it affect the threshold range of relative translation gains, a Redirected Walking (RDW) technique that scales the user’s movement in virtual space in different ratios for the width and depth. While previous studies assert that a virtual room’s size affects relative translation gain thresholds on account of the virtual horizon’s location, additional research is needed to explore this assumption through a structured approach to visual perception in Virtual Reality (VR). We estimate the relative translation gain thresholds in six spatial conditions configured by three room sizes and the presence of virtual objects (3 × 2), which were set according to differing Angles of Declination (AoDs) between eye-gaze and the forward-gaze. Results show that both size and virtual objects significantly affect the threshold range, it being greater in the large-sized condition and furnished condition. This indicates that the effect of relative translation gains can be further increased by constructing a perceived virtual movable space that is even larger than the adjusted virtual movable space and placing objects in it. Our study can be applied to adjust virtual spaces in synchronizing heterogeneous spaces without coordinate distortion where real and virtual objects can be leveraged to create realistic mutual spaces.

Space-adaptive algorithms aim to effectively align the virtual with the real to provide immersive user experiences for Augmented Reality(AR) content across various physical spaces. While such measures are reliant on real spatial features, efforts to understand those features from the user’s perspective and reflect them in designing adaptive augmented spaces have been lacking. For this, we compared factors of narrative experience in six spatial conditions during the gameplay of Fragments, a space-adaptive AR detective game. Configured by size and furniture layout, each condition afforded disparate degrees of traversability and visibility. Results show that whereas centered furniture clusters are suitable for higher presence in sufficiently large rooms, the same layout leads to lower narrative engagement. Based on our findings, we suggest guidelines that can enhance the effects of space adaptivity by considering how users perceive and navigate augmented space generated from different physical environments.

We propose the concept of relative translation gains, a novel Redirected Walking (RDW) method to create a mutual movable space between the Augmented Reality (AR) host's reference space and the Virtual Reality (VR) client's space. Previous RDW methods have focused on maximizing the movable space at the expense of aligning the coordinates between the AR and VR side, and could only be applied to collaborative scenarios involving sequential tasks. Our method solves these problems by adjusting the remote client's walking speed for each axis of a VR space to modify the movable area without coordinate distortion. We estimate the relative translation gain threshold, defined as the extent to which the walking speed can be altered without creating a perceived difference in distance. In order to reflect features of the reference space in generating the mutual space, we then examine how changing its size affects the threshold value. Our study showed that for remote clients connected to the larger reference space, relative translation gains can be increased to utilize a VR space bigger than their real space. Our method can be applied to create optimal mutual spaces for a wider variety of asymmetric Mixed Reality (MR) remote collaboration systems.

One of the main challenges in creating narrative-driven Augmented Reality (AR) content for Head Mounted Displays (HMDs) is to make them equally accessible and enjoyable in different types of indoor environments. However, little has been studied in regards to whether such content can indeed provide similar, if not the same, levels of experience across different spaces. To gain more understanding towards this issue, we examine the effect of room size and furniture on the player experience of Fragments, a space-adaptive, indoor AR crime-solving game created for the Microsoft HoloLens. The study compares factors of player experience in four types of spatial conditions: (1) Large Room - Fully Furnished; (2) Large Room - Scarcely Furnished; (3) Small Room - Fully Furnished; and (4) Small Room - Scarcely Furnished. Our results show that while large spaces facilitate a higher sense of presence and narrative engagement, fully-furnished rooms raise perceived workload. Based on our findings, we propose design suggestions that can support narrative-driven, space-adaptive indoor HMD-based AR content in delivering optimal experiences for various types of rooms.