pupil swim

Pupil swim is geometric distortion in VR scene features
made visible by movements.

Distortions when panning fixed text are noted,

as in the example @ 0:19/0:41 of this video

Pupil swim becomes evident
during Vestibulo-ocular pupil movements
that compensate for head repositioning.

Pupil swim can be reduced
by digitally pre-warping scenes.

Eyebox is the small space where a lens yields best images.

For e.g. microscope and telescope eyepieces,
eyebox is centered at some distance called eye relief.
Resolution and sharpness outside eyebox
drop as aberrations increase.

Even within a nominal eyebox,
abberations can provoke pupil swim
in static scenes for pupils moving relative to headset.

Almalence demonstrates that pupil swim