Contextual Blocking Entities: Transformation of Guardian Boundaries in Virtual Reality

Conventional Virtual Reality (VR) guardian systems communicate physical boundaries through grid-based overlays that effectively signal spatial limits, but disrupt narrative coherence and presence. To address this safety-presence trade-off, we propose Contextual Blocking Entities (CBEs), a boundary design approach that transforms guardian boundaries into narrative-integrated virtual objects by embedding spatial constraints within the internal logic of the virtual world. We define CBE design through three dimensions, Function Match, which signals impassability through visual form, Context Consistency, which determines how naturally the object belongs to the world, and Constraint Type, which determines how the boundary geometry engages spatial processing. To operationalize these dimensions, we first conducted a formative study classifying 80 candidate virtual objects, then carried out a controlled within-subject user study using a 2×2×2 factorial design to compare CBE conditions against a grid baseline across presence, spatial awareness, and boundary compliance. All CBE conditions produced significantly higher presence than the grid baseline, while four conditions showed no significant difference from the baseline in boundary violations and all conditions maintained comparable Mean Return Time. The three dimensions played asymmetric roles across boundary interaction. Function Match supported approach deterrence and conservative spatial estimation, Context Consistency supported post-violation correction, and Constraint Type shaped actual movement range more strongly than explicit spatial judgment. These findings show that the safety-presence trade-off depends on how spatial constraints are expressed, yielding practical guidelines for CBE selection and placement in room-scale VR.