Hi @stimulant, The EyeX allows for free head movements while a user’s head is located within a track box, which has the shape of a frustum with the vertex positioned in the center of the device. Thus, the allowable horizontal and vertical head movements change as a function of the distance of the user from the screen.
For example, at a distance of 700mm users may move their head 240mm leftwards or rightwards and 195mm upwards or downwards. The maximum recommended screen size is 24 inches. Considering a user positioned at the far limit of the operating distance (800 mm), the working range of the device in degrees of visual angle is [−18°, 18°] on the x-axis, and [−10.5°, 10.5°] on the y-axis. The device will likely provide gaze estimates at wider gaze angles, to the detriment however of accuracy and precision, particularly in the corners of the monitor. -Gibaldi, A., Vanegas, M., Bex, P.J. et al. Behav Res (2016).
Hope this answers your question!