Figure 4.

Gaze accuracy and the 3-D reference frame transformations for gaze-shifts. Rightward gaze-shifts are simulated from five different vertical altitudes with either a fixed symmetric horizontal gaze-shift, −40 cm left to 40 cm right, on a flat target screen (A–C), or from the same initial positions with a fixed retinal error of 60° right (D–F). First row shows the initial and desired target positions on the screen and the development of gaze direction on the screen during the gaze-shift. Second row shows the development of the target position in retinal coordinates during gaze-shift. Third row shows the development of the 2-D angular gaze position during gaze-shift. For both conditions, the model parameters are set to α = β = δ = 0.5. Circles show initial target locations while stars show the desired positions of target. Note that in (B) even though the targets are due right in spatial coordinates, they have variable vertical components in retinal coordinates, whereas conversely retinal errors in (E) start and end at the same positions, and correspond to different gaze trajectories.