arXiv subjects

Timothy N. Welsh

Publications and source records attributed to Timothy N. Welsh.

4 recordsLinked to original sources

arXiv2026

Divergent Perceptuomotor Recalibration in Virtual Reality and Video-Passthrough Mixed Reality on the Same Head-Mounted Display

Virtual reality (VR) and video-passthrough mixed reality (MR-VPT) can be delivered on the same headset, but it is unclear whether these two interaction modalities produce comparable perceptuomotor behavior. Although delivery through the same headset controls many display-level characteristics, VR and MR-VPT differ in both their visual-feedback pipelines and the action-relevant visual information available to guide movement, such as whether the surrounding environment and the user's body are synthetically rendered or preserved through passthrough. This study compared visually guided manual pointing in VR and MR-VPT using the same headset. Forty adults were assigned to either a VR or MR-VPT group and completed a pointing task in the physical, unmediated reality (UR) before and after performing the same task in their assigned XR modality. The analyses revealed numerous important insights. First, groups had comparable baseline performance in UR prior to XR exposure. Second, the two modalities produced opposite initial biases during XR exposure: the VR group undershot the target, whereas the MR-VPT group overshot. Third, although both groups reduced error with continued exposure to XR, there were differences in the patterns of adaptation: the VR group adapted more slowly and exhibited stronger distance-dependent undershooting than the MR-VPT group. Finally, after XR exposure, both groups showed significant undershooting aftereffects with the VR group retaining a persistent residual undershoot, suggesting incomplete de-adaptation. The results suggest that perceptuomotor recalibration is shaped not only by display-level constraints but also by the action-relevant visual information available within the interaction environment. These findings highlight the need to validate perceptuomotor interaction techniques separately in VR and MR-VPT, even when they are implemented on the same hardware.

cs.HC↗

arXiv2026

Dissociable Spatial and Temporal Effects of Interaction Latency in Virtual Reality

Motion-to-photon latency is inherent in immersive virtual reality (VR) systems and can arise from multiple sensorimotor loops, including view-contingent latency between head movement and display update and interaction latency between hand movement and the virtual effector. Although prior work shows that interaction latency can impair VR performance, it remains unclear whether common spatial, temporal, and efficiency measures reveal the same latency-related disruption. This study addressed this question by experimentally imposing delays between the physical and virtual hands during manual pointing in VR. Participants pointed to targets on a horizontal surface in VR and in the physical environment as an unmediated baseline. In VR, pointing was performed with a virtual hand avatar controlled by a motion capture pipeline, and additional delays (0-500 ms) were imposed between the participant's hand movement and the rendered movement of the virtual hand. Relative to the baseline, performance in VR showed greater endpoint error, longer movement time, greater endpoint variability, and lower throughput. Within VR, added interaction latency further increased endpoint error and variability, reduced throughput, and altered movement time, but these effects followed different profiles: endpoint error increased even at the shortest delays, whereas movement time remained stable at short delays and increased primarily at longer delays. These findings show that interaction latency produces dissociable spatial and temporal consequences in immersive VR, such that endpoint accuracy revealed disruption before movement time or throughput. Thus, latency-sensitive VR interactions cannot be fully evaluated using movement time or efficiency measures alone. Instead, HCI evaluations should assess both spatial and temporal performance, particularly when VR tasks involve visually guided manual actions.

cs.HC↗

arXiv2025

Virtual Reality Alters Perceived Functional Body Size

Virtual reality (VR) introduces sensory perturbations that may impact perception and action. The current study was designed to investigate how immersive VR presented through a head-mounted display (HMD) affects perceived functional body size using a passable aperture paradigm. Participants (n=60) performed an action task (sidle through apertures) and a perception task (adjust aperture width until passable without contact) in both physical, unmediated reality (UR) and VR. Results revealed significantly higher action and perceptual thresholds in VR compared to UR. Affordance ratios (perceptual threshold over action threshold) were also higher in VR, indicating that the increase in perceptual thresholds in VR was driven partly by sensorimotor uncertainty, as reflected in the increase in the action thresholds, and partly by perceptual distortions imposed by VR. This perceptual overestimation in VR also persisted as an aftereffect in UR following VR exposure. Geometrical modelling attributed the disproportionate increase in the perceptual threshold in VR primarily to depth compression. This compression, stemming from the vergence-accommodation conflict (VAC), caused the virtual aperture to be perceived as narrower than depicted, thus requiring a wider adjusted aperture. Critically, after mathematically correcting for the VAC's impact on perceived aperture width, the affordance ratios in VR became equivalent to those in UR. These outcomes demonstrate a recovered invariant geometrical scaling, suggesting that perception remained functionally attuned to action capabilities once VAC-induced distortions were accounted for. These findings highlight that VR-induced depth compression systematically alters perceived body-environment relationships, leading to an altered sense of one's functional body size.

cs.HC↗

arXiv2025

Investigating A Geometrical Solution to the Vergence-Accommodation Conflict for Targeted Movements in Virtual Reality

While virtual reality (VR) holds significant potential to revolutionize digital user interaction, how visual information is presented through VR head-mounted displays (HMDs) differs from naturalistic viewing and interactions in physical environments, leading to performance decrements. One critical challenge in VR development is the vergence-accommodation conflict (VAC), which arises due to the intrinsic constraints of approximating the natural viewing geometry through digital displays. Although various hardware and software solutions have been proposed to address VAC, no commercially viable option has been universally adopted by manufacturers. This paper presents and evaluates a software solution grounded in a vision-based geometrical model of VAC that mediates VAC's impact on movement in VR. This model predicts the impact of VAC as a constant offset to the vergence angle, distorting the binocular viewing geometry that results in movement undershooting. In Experiment 1, a 3D pointing task validated the model's predictions and demonstrated that VAC primarily affects online movements involving real-time visual feedback. Experiment 2 implemented a shader program to rectify the effect of VAC, improving movement accuracy by approximately 30%. Overall, this work presented a practical approach to reducing the impact of VAC on HMD-based manual interactions, enhancing the user experience in virtual environments.

cs.HC↗