Graphics Reference
In-Depth Information
Figure 1.10.
Correct wrapped diffuse lighting from rectangular (top) and disk (bottom)
area light.
Intersect a ray from
p
in direction
h
with the light plane creating point
p
d
. This is the most important point in terms of importance sampling.
◦
Treat vector
−
pp
d
as a light vector for the diffuse equation, effectively
approximating the diffuse integral from equation (1.11):
Diffuse
(
p,ω
o
)=
L
n
A
(
n
)
◦
C
d
cos
θdω
i
(
n
)
∼
L
n
C
d
cos
θ
−−→
pp
d
dω
−−→
pp
d
.
(1.15)
In equation (1.15) we assume that
L
n
is constant for the whole area of the
light. The angle between the new light vector
−
pp
d
and surface normal
n
is
θ
−−→
pp
d
.
