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240 10. Stereopsis
riencing positive, negative or zero parallax. As the value of t approaches d,
the viewer can start to feel uncomfortable. As it exceeds d, divergent parallax
is being simulated, and the natural viewing perception is lost. For example,
sitting in front of a workstation where the average viewing distance is about
18 in., a good and comfortable stereoscopic effect can be obtained with a
parallax separation of about
1
2
in., equivalent to an angular parallax of 3
◦
.
When rendering images with the intention of providing a parallax sep-
aration of
1
2
in. on a typical monitor, it is necessary to determine the sepa-
ration between the