The sequence of experiments described in Section C.2 explored the effect of a foreground occlusion on an inside-out display roll-correction task. For these experiments, the foreground occlusion was a black, monocular iris mounted on a desk in front of a 20'' monitor. The iris could be adjusted to narrow or widen the FOV. The iris was mounted in such a way that its height could be easily altered to provide each participant with a comfortable seated view of the monitor through the foreground occlusion. An adjustable padded chinrest was also provided. The iris and chinrest were surrounded by black tarp which blocked out any peripheral visual cues from the laboratory. After choosing which eye to use for the trials, participants were fitted with an eyepatch which blocked the other eye. This avoided binocular rivalry distractions without the need for squinting. Room lights were turned off so that illumination came almost entirely from the monitor.
The monitor displayed a circular scene surrounded by a black annulus which covered the remainder of the screen. In the foreground occlusion condition, participants were asked to narrow the iris so that they could just barely see a red circle just inside the annulus. Thus, the iris blocked out all visual cues closer than the scene. To provide matched trials without the foreground occlusion, participants expanded the iris to match a red circle such that the black annulus surrounding the scene was clearly visible. In both conditions, the red circle disappeared prior to the start of the trials.
The monitor was viewed from a distance of about 20 cm. The FOV of the scene was about 30. The red circle for the foreground occlusion condition was set at about 27. In the wider condition, the FOV was about 45.