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gaze contingent displays degrade resolution of peripheral image regions in order to reduce computational effort during
image transmission, retrieval or display

hi resolution region moves with users focus of attention -- tracked by eye tracker

GCDs help increase display speed through compression of peripheral image information
GCDS match resolvability of human vision so can be used to educate about the perceptual and performance consequences of 
vision loss

GCDs can either be screen based or model based.
screen based depends on image processing and model relies on graphics primitives

they have progressed from image based stimuli (sine waves) to complex image based stimuli (images/videos) to model based
stimuli (3d models)

AUIs are an instance of non-command interfaces, where screen objects or physical devices are controlled
by gaze.

In graphical systems, model-based methods aim at reducing resolution by directly manipulating graphical model geometry 
prior to rendering
real time or gaze contingent model manipulations has the benefit of display speedup in immersive displays or complex
graphical environments

does the resolution degredation/rendering time have a noticeable impact for the user? either performance based or perceptual?

Parkhurst and Niebur evaluated 2 perceptually adaptive rendering techniques - one velocity dependent and one gaze contingent.

Decreasing gaze contingent peripheral geometric detail was found to increase object detection reaction times. Reaction
times to localize a target, however, decreased. 

For environments containing significant topological detail, such as virtual terrains or complex objects,
rendering with multiple levels of detail, where the level is based on user position and gaze direction,
is essential to provide an acceptable combination of surface detail and frame rate

in one test case unattended scene objects are modeled with fewer polygons, even when they are not distant in the scene.
tracking the gaze with a monocular eye tracker to measure the viewers real time location of gaze, gaze contingent 
level of display reduction was found to lead to substantial performance improvements

another approach to gaze contingent modelling was done by O'Sullivean who considered temproal resolution in the periphery.
he developed a degradable collision handling mechanism to limit object collision resolution outside the central display region

Highly prioritized object collisions in the central region are allocated more processing time so that the contact model and 
visual response is more believeable.
he noticed a fall off in collision detection accuracy at about a 4 degrees visual angle, developed a gaze-contingent
collision handling system and reported an overall improvement in the perception of the tracked
simulation when the central region was synchronized to the viewerâ€™s gaze.


A related display variant to GCDs which are not necessarily gaze-contingent but share the foveal/
peripheral demarcation are focus plus context screens. Focus plus context screens achieve the highdetail/
low-detail effect by combining a large, wallsized low-resolution display with an embedded
high-resolution screen.

for example a large map in low resolution with moveing cars on it in high resolution

technical aspects of GCDs