This paper introduces the Simultaneous Presence (SP) Continuum, a novel concept designed to enhance the use of portals in virtual reality (VR) by understanding users' experiences across multiple environments. Portals traditionally provide access to secondary worlds, but their limited field of view (FoV) can hinder full engagement with these environments. To overcome this, we introduce portal overlays, which expand the portal's FoV by superimposing the secondary world over the user's view of the primary world. We explore several overlay techniques-Contours, Blended (Opacity and Stencil), and Absolute-to adjust user experience across the SP Continuum. The Contours overlay, renders only the edges of objects, offering a minimalistic view and immersion of the secondary world. The Blended overlay allows for adjustable immersion between worlds through opacity or the distribution of pixels. The Absolute overlay virtually immerses users completely in the secondary world. Importantly, these overlays are context-activated instead of always on, to suit situational needs. Our study revealed high SP was possible in both worlds, and overlays significantly impacted users' experiences on the SP Continuum. The Blended overlay provided balanced SP, while Contours had the highest primary presence but lower secondary presence. In contrast, the Absolute overlay, alternating full immersion between worlds, had the highest secondary presence but resulted in reduced primary presence, slower navigation and selection times, higher effort and frustration, and lower usability.

This paper introduces foundational techniques for Adaptive Portals (AP); portals that adjust to users’ needs in Virtual Reality (VR). At the forefront of our contributions is the AP-Reach technique, with Entry and Exit strategies, designed to overcome the spatial limitations of portals and VR, enabling users to comfortably extend their reach to objects beyond their immediate vicinity. In parallel, we present PH-Reach as an alternative to the AP concept, also aimed at extending user reach inside portals. The effectiveness of these reach techniques is evaluated through a comparative user study, which compared Entry AP-Reach, Exit AP-Reach, and PHReach techniquesagainst traditional natural reach as a baseline. Results show Exit AP-Reach surpassed both its counterparts and the baseline to various degrees in terms of reducing task completion time, physical movement/demand, effort, and frustration. Additionally, this paper introduces AP-Bounds and AP-Restriction.

This paper introduces Point & Portal, a novel Virtual Reality (VR) interaction technique, inspired by Point & Teleport. This new technique enables users to configure portals using pointing actions, and supports seamless action at a distance and navigation without requiring line of sight. By supporting multiple portals, Point & Portalenables users to create dynamic portal configurations to manage multiple remote tasks. Additionally, this paper introduces Relative Portal Positioning for reliable portal interactions, and the concept of maintaining Level Portals. In a comparative user study, Point & Portal demonstrated significant advantages over the traditional Point & Teleport technique to bring interaction devices within-arm’s reach. In the presence of obstacles, Point & Portal exhibited faster speed, lower cognitive load and was preferred by participants. Overall, participants required less physical movement, pointing actions, and reported higher involvement and “good” usability.

Transformative portals are a novel technique for supporting visualizations and interactions between locations that are not co-located in virtual reality (VR). We are interested in improving upon current portal rendering for VR, and supporting VR users to create new portals quickly and accurately. In this paper, we introduce a new high-level algorithm for rendering transformative portals in VR and present the benefits of our approach. By leveraging single-pass stereo and stencil portal rendering, we developed our algorithm to support multiple portals with “infinite” recursion, while running performant on mobile VR devices. We then benchmarked our performance against other common portal rendering implementations. In addition, we focused our research on VR interactions for handheld portals, in which the initial placement of the portal’s destination is imperative to its effectiveness. In this paper, we present four new portal creation interactions for handheld portals: fishing reel, raycast with fishing reel, marker, and projectile curve. Based on existing research, we also established standard controls for fine-grained portal manipulation. In a user study, we compared and evaluated how well the creation interactions performed and argue that projectile curve is the most suitable general-purpose technique.