The geometry of the vergence-accommodation conflict in mixed reality systems.

Mixed reality technologies, such as virtual (VR) and augmented (AR) reality, present promising opportunities to advance education and professional training due to their adaptability to diverse contexts. Distortions in the perceived distance in such mediated conditions, however, are well documented and have imposed nontrivial challenges that complicate and limit transferring task performance in a virtual setting to the unmediated reality (UR). One potential source of the distance distortion is the vergence-accommodation conflict-the discrepancy between the depth specified by the eyes' accommodative state and the angle at which the eyes converge to fixate on a target. The present study involved the use of a manual pointing task in UR, VR, and AR to quantify the magnitude of the potential depth distortion in each modality. Conceptualizing the effect of vergence-accommodation offset as a constant offset to the vergence angle, a model was developed based on the stereoscopic viewing geometry. Different versions of the model were used to fit and predict the behavioral data for all modalities. Results confirmed the validity of the conceptualization of vergence-accommodation as a device-specific vergence offset, which predicted up to 66% of the variance in the data. The fitted parameters indicate that, due to the vergence-accommodation conflict, participants' vergence angle was driven outwards by approximately 0.2°, which disrupted the stereoscopic viewing geometry and produced distance distortion in VR and AR. The implications of this finding are discussed in the context of developing virtual environments that minimize the effect of depth distortion.

Prolonged exposure to mixed reality alters task performance in the unmediated environment.

The popularity of mixed reality (MR) technologies, including virtual (VR) and augmented (AR) reality, have advanced many training and skill development applications. If successful, these technologies could be valuable for high-impact professional training, like medical operations or sports, where the physical resources could be limited or inaccessible. Despite MR's potential, it is still unclear whether repeatedly performing a task in MR would affect performance in the same or related tasks in the physical environment. To investigate this issue, participants executed a series of visually-guided manual pointing movements in the physical world before and after spending one hour in VR or AR performing similar movements. Results showed that, due to the MR headsets' intrinsic perceptual geometry, movements executed in VR were shorter and movements executed in AR were longer than the veridical Euclidean distance. Crucially, the sensorimotor bias in MR conditions also manifested in the subsequent post-test pointing task; participants transferring from VR initially undershoot whereas those from AR overshoot the target in the physical environment. These findings call for careful consideration of MR-based training because the exposure to MR may perturb the sensorimotor processes in the physical environment and negatively impact performance accuracy and transfer of training from MR to UR.