Graphics Reference
In-Depth Information
Y-axis
mouse click is
(x
ndc
, y
ndc
, 0)
on near plane
(x
ndc
, y
ndc
, z
ndc
)
is a line
NDC
Cube
X-axis
exists at
(x
ndc
, y
ndc
, -1)
on far plane
Z-axis
Figure 15.12.
DC point is an NDC ray.
NDC-to-EC transform.
Remember that the NDC cube is transformed from a
view frustum. Figure 15.13 shows the view frustum in EC space and the corre-
sponding NDC cube. From this figure, we see that
transforms
←→
p
n
p
n
p
e
p
e
and
transforms
←→
p
n
p
n
p
e
p
e
.
We see that line segments that are parallel to the
z
-axis in NDC space transform
into projection rays in EC space. Let
p
n
x
n
,
y
n
,
z
n
)
,
=(
p
n
x
n
,
y
n
,
z
n
)
,
=(
p
e
x
e
,
y
e
,
z
e
)
,
=(
p
e
x
e
,
y
e
,
z
e
)
.
=(
In general,
y
e
y
n
=
y
e
y
n
,
or
y
n
y
e
y
e
=
y
n
.
(15.7)
In Figure 15.13,
y
n
=
1
.
0
,
(15.8)
y
e
=
n
tan
(
α
)
,
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