Jim Helman (jimh++at++surreal)
Mon, 13 Nov 95 10:39:52 -0800
The explanation is quite simple. If your eye is tracking an object as
it moves across the screen, e.g. a telephone pole. Your eye is moving
at a continuously, tracking the average motion of the object. But
with a 30Hz frame rate, the object itself is being drawn in the same
location on the screen at two instants 1/60th of a second apart.
During this 1/60th of a second, your eye's direction has moved
slightly causing the telephone pole to be imaged at a slightly
different position on the retina than the previous one. This results
in two images on the retina (ghosting or doubling) when rendering at
30Hz, three images at 20Hz, and so on.
Some solutions are to render at the video rate, to reduce the rates of
motion such that the distance separating the images is very small, or
to reduce the contrast of edges in the scene.
In field sequential color displays (e.g. 180Hz R+G+B), the same
artifact appears. With a 60Hz frame rate on 180Hz field sequential,
you see three ghosts each with a different color, which gives the
illusion of little rainbows along high contrast edges.
rgds,
-jim helman
jimh++at++surreal.asd.sgi.com
415/933-1151
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