Portals in Impossible VR Spaces: A Taxonomy and Effects on Spatial Memory

In virtual reality (VR), portals serve as a common metaphor for relocation, allowing users to navigate large virtual environments. However, portal design is often ad hoc, leaving developers without clear principles for their intentional design and placement to support specific experiential or performance goals. We present a taxonomy for VR portals, deconstructing them into three main dimensions: World-related, Portal-related, and User-related. Based on the suggested taxonomy, we implemented eight unique portals varying across three categories: World Integration (Integrated vs. Non-Integrated), Nature Definition (Obvious vs. Subtle/Hidden), and Destination Visibility (Preview vs. Occluded). We assess the impact of these factors, focusing on spatial memory, presence, and experience in a user study with 32 participants. Our results show that World-Integrated portals improve spatial memory and realism, while the exposure of portal’s unusual Nature mainly affects perceived realism. Visibility of the portal’s Destination positively affected user comfort, acceptance, and presence. We discuss the insights for the intentional design of a portal-based relocation techniques that support comfortable and intuitive navigation. Such techniques are particularly suitable for small physical spaces, where portals enable space-efficient, self-overlapping virtual architectures.