Retinal optic flow during natural locomotion
Fig 2
Retinal vs head-centered optic flow.
Optic flow patterns (down-sampled) for a sequence of 5 video frames from S3 Video, altered for visibility in print. Head centered flow shows optic flow in the reference frame of the head mounted “world” camera, and represents optic flow free from the effects of eye movements. Retinal flow shows optic flow in the references frame of a spherical pinhole camera stabilized on the subject’s fixation point. Purple and white lines show the integral curves of the measured flow fields, determined by using the streamlines2 function in Matlab to make a grid of particles drift along the negation of the flow fields measured by the DeepFlow optical flow detection algorithm in OpenCV. The red trace shows the movement of the head-centered FoE moving down and to the right across the 5 frames. In contrast, note the stability of the retina-centered flow over the same period.