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10.1. Parallax 245
Figure 10.8. Parallax geometry. The plane of zero parallax is at the front of the scene.
To determine d, write tan
2
=
P
max
/2
y
=
d/2
L
+ y
then d = P
max
(1 +
L
y
).
(Note: P
max
and P
min
are measured in the units of the world coordinate sys-
tem.)
In the case where we want the minimum angular parallax
min
= 0
◦
,the
distance of zero parallax is D
zpx
= y
min
= L
. The equality with L is true
because it is usually assumed that the plane of zero parallax lies at the average
distance between viewpoint and objects in the scene (see Figure 10.8).
To satisfy this constraint, the cameras must be separated by a distance d
(in world coordinate units) given ...