Eye tracking white sclera (limbus tracking). It presents another challenge for vertical eye movements due to obstruction of eyelids. Eye-tracking setups vary greatly: some are head-mounted, some require the head to be stable (for example, with a chin rest), and some function remotely and automatically track the head during motion. Most use a sampling rate of at least 30 Hz. Although 50/60 Hz is more common, today many video-based eye trackers run at 240, 350 or even 1000/1250 Hz, speeds needed in order to capture fixational eye movements or correctly measure saccade dynamics. Eye movements are typically divided into fixations and saccades
Eye of the Serpent civilization. If the scenario is played as a one-on-one scenario, the player character is accompanied by three non-player characters. UK5 "Eye of the Serpent" was written by Graeme Morris, with art by Tim Sell and was published by TSR in 1984 as a 32-page booklet with an outer folder. It is part of the UK-series of modules, written by British authors and developed by TSR's UK division. Chris Hunter reviewed the module for "Imagine" magazine, giving it a mixed review. Hunter described the scenario as climbing down a "rather artificial looking" mountain side. This constitutes the main part of the