Toward a More Standardized Multi-directional Tapping Task in VR: The Effect of Target Depth

The multi-directional tapping task has long served as a foundational tool for evaluating pointing performance in human-computer interaction research. However, its transition from 2D interfaces to virtual reality (VR) raises challenges, especially in standardizing target depth. This study explores how target depth influences performance in VR, focusing on two common techniques: Raycasting and Virtual Hand. We conducted two controlled experiments (each with $\mathrm{n}=20$) to isolate depth effects. In Experiment 1, fixed target size led to visual angle (VA) shifts across depths, affecting performance. Both techniques performed best when VA was between $1-4^{\circ}$; Raycasting peaked at 2 m, Virtual Hand at $0.4-0.5 ~\mathrm{m}$. In Experiment 2, we controlled VA to isolate depth itself. Raycasting remained stable beyond 2 m but degraded at close range due to biomechanical limits. Virtual Hand remained sensitive to depth despite fixed VA, but differences were smaller, with throughput unaffected. These results suggest VA should be the primary parameter for standardizing the task in VR. Depth-specific evaluation remains necessary, except for Raycasting beyond 2 m. We provide depth-aware guidelines to improve standardization and comparability while aligning with ISO protocols.