Irrespective of the ability of a VR system to simulate the visual cues
necessary for the perception of three dimensions, the strength or
weakness of the illusion is also dependent upon the quality and update
rate of the final image, and the responsiveness of the system to user
input.
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Image quality is dependent upon a
number of factors, some of which can be traded off against each other.
Generally speaking, the visual quality of a 3D scene improves with the
detail of its geometric and surface description, but this comes at the
cost of a larger processing overhead. At the same time there is a need
for a rapid and consistent image update rate so that movement is
perceived as continuous. The update rate is dependent not only upon
processing power, but also on the refresh rate of the display system.
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System response time (also referred to as latency) is the
time lag between a user input (e.g. tracker movement) and this change
being reflected by the display. Part of this lag is accounted for by
the finite image update rate, while the rest is due to the time taken
to propagate and process the user input.