Retinal optic flow during natural locomotion
Fig 9
A representative flow field during a perfect 250ms fixation (stabilized) and when undergoing 1 degree of slip.
An eye translation direction downwards and slightly to the left of fixation is examined. The top row shows the stabilized case (i.e. perfect fixation) and the second row shows the unstabilized case (i.e. retinal slip). The bottom row shows the difference between the two, calculated by simple subtraction. The two plots on the left show the flow fields for the stabilized and unstabilized cases, and are very similar qualitatively, with the focus of expansion slightly shifted in the opposite of motion slippage. The plots on the right are centered on the fovea, and show velocity fields, curl, and divergence values. During stabilization, velocities are low with 0 deg/s at the fovea due to simulated perfect fixation. For stabilization with slip, velocity at the fovea is 4.17 deg/s and velocities at other retinal locations are shifted either higher or lower depending on location, however the magnitude of this shift does not exceed the foveal slip. There are small changes in the curl and divergence fields but the patterns are very similar.