A Quest for Co-Located Mixed Reality: Aligning and Assessing SLAM Tracking for Same-Space Multi-User Experiences

Abstract

Current solutions for creating co-located Mixed Reality (MR) experiences typically rely on platform-specific synchronisation of spatial anchors or Simultaneous Localisation and Mapping (SLAM) data across clients, often coupled to cloud services. This introduces significant costs (in development and deployment), constraints (with interoperability across platforms often limited), and privacy concerns. For practitioners, support is needed for creating platformagnostic co-located MR experiences. This paper explores the utility of aligned SLAM solutions by 1) surveying approaches toward aligning disparate device coordinate spaces, formalizing their theoretical accuracy and limitations; 2) providing skeleton implementations for audience-based, small-scale and large-scale co-location using said alignment approaches; and 3) detailing how we can assess the accuracy and safety of 6DoF/SLAM tracking solutions for any arbitrary device and dynamic environment without the need for an expensive ground truth optical tracking, by using trilateration and a $30 laser distance meter. Through this, we hope to further democratise the creation of cross-platform co-located MR experiences. CCS CONCEPTS • Human-centered computing → Virtual reality; • Computing methodologies → Mixed / augmented reality;

PassengXR: A Low Cost Platform for Any-Car, Multi-User, Motion-Based Passenger XR Experiences

“…This is challenging because XR headsets rely on in-built IMUs to track headset orientation changes, however these will also sense vehicle orientation changes. Moreover, 6DoF headsets rely on Visual Inertial Odometry (VIO [42]) / Simultaneous Localization and Mapping (SLAM [7,31]), fusing this IMU data with optical data about the local environment [53] to track the relative or global position of the headset. However this visual information is largely conflicting -capturing both the static and stable vehicle interior, and also the changing, moving exterior environmentwhich can undermine inside-out positional tracking.…”

Exploring User Behaviour in Asymmetric Collaborative Mixed Reality

“…To establish a shared coordinate system between the AR user and VR user, the CVE was aligned with the physical room of the AR user. We used a manual alignment procedure based on two known points 𝑄1 and 𝑄2, located on two corners of a large table, as described by McGill et al [24]. Upon the first launch of the system on the HL2, an initial calibration was needed.…”

Safety, Power Imbalances, Ethics and Proxy Sex: Surveying In-The-Wild Interactions Between VR Users and Bystanders

“…Scavarelli et al investigated notifications to prevent collisions between a VR user and nearby persons [46]. Others, meanwhile, have explored augmented reality (AR) systems to allow a bystander to better visualise the VR user's view in VR [35,44,50]. Gugenheimer et al took this a step further and built novel, cross reality experiences to encourage a bystander to directly interact with a VR user's virtual environment [15,18,19,22].…”

“…VR is often used in shared, social settings, but interactions between VR users and bystanders (those physically near the VR user but who cannot directly interact with the VR user's virtual environment) in uncontrolled social settings are not well understood. Recent work has investigated a range of systems to increase a VR user's awareness of nearby bystanders [14,34,36,40,54] and to facilitate interactions with them [18,19,25,33,35,57]. However, surprisingly little is known about VR usage within the real world settings where these systems might be used.…”