
2.3 Cameras 47
Similarly, an inner-pointing, unit-length normal and the bottom plane are
N
b
=
d
min
U − u
min
D
d
2
min
+ u
2
min
, N
b
.
(X − E) = 0 (2.56)
An inner-pointing, unit-length normal and the top plane are
N
t
=
−d
min
U + u
max
D
d
2
min
+ u
2
max
, N
t
.
(X − E) = 0 (2.57)
It is common when choosing a camera model to have an orthogonal view frus-
tum. The frustum is symmetric in that u
min
=−u
max
and r
min
=−r
max
. The four
independent frustum parameters are d
min
, d
max
, u
max
, and r
max
. An alternate way to
specify the frustum is to use the field of view in the U direction and the aspect ra-
tio for the viewport. In Figure 2.16 (c), the field of view is the angle 2θ
u
. The aspect ...