“…To share the VR content of an HMD user with others, recent commercial HMDs have a function that mirrors the content onto other screens (e.g., [1,12]). Many previous studies also used external devices, such as desktop displays [81], touch displays [17,26,31,73], projections [14,23,28,79], and a CAVE-based display [32] to share VR content with nearby non-HMD users, where non-HMD users may be invited to interact with it. However, they require additional setup in advance and might not be suited for ad-hoc interaction [38] in mobile VR scenarios.…”