Unity platform

The VR BBT simulation was developed using the Unity platform (Unity Technologies, Austin TX, USA). Using Unity as the real-time simulation engine, the VR BBT simulation is completed using the Oculus Rift VR system on a 16 GB RAM Windows PC with an Intel Core i7-8700 processor. The BBT simulation features a set of logical constraints that align with the rules of the physical BBT. The virtual BBT is developed to have the same dimensions as the physical BBT within the virtual environment [53.7 cm (W) × 25.4 cm (H) × 8.5 cm (D)]. The virtual environment includes an enclosed room with 3 windows, a background made to look like a starry night, and a white scoreboard that displays a 1-min timer and BBT score directly in front of the user. The VR BBT simulation was developed in first-person perspective and the virtual avatar was represented as floating hands within the simulation space that the participants controlled (Fig. 6).Figure 6

Comparison of the VR BBT simulation (top) setup to the physical BBT (bottom setup).

The experiment was controlled by a desktop computer running an HTC Vive Virtual Reality device equipped with an SMI eye tracker. The HTC Vive headset has a resolution of 1080 x 1200 pixels, with a 110° by 113° field of view and a refresh rate of 90 Hz. The virtual experimental set-up was built using the Unity platform (Unity Technologies, 2017) [31 ]. The SMI eye tracker has a sampling rate of 250 Hz and was controlled using the SMI-designed Unity plugin. Tracking accuracy was maintained by performing a calibration every 20 trials. Calibration consisted of following a moving white circle with a red dot in the middle to 5 different regions. The SMI Unity plugin reports only success or failure of calibration, not accuracy, so calibration was repeated upon failure. Head movements (movements of the HTC Vive headset) were tracked using inertial measurement units inside the headsets that were calibrated via two infrared base stations (60 Hz) located on opposite corners of the room [32 (link)].