Game Development Reference
In-Depth Information
Chapter 7 Summary
Point Light Source Attenuation
The intensity of a point light source at a distance d from its position is given by
1
=
,
0
kkdkd
++
2
c
l
q
where is the color of the light, and the constants k , k , and k control the at-
tenuation.
Spot Light Source Attenuation
The intensity of a spot light source at a point Q lying at a distance d from the
light's position is given by
p
{
}
max
−⋅
RL
, 0
=
,
0
2
kkdkd
++
c
l
q
where is the color of the light; k , k , and k are the attenuation constants; R is
the direction in which the spot light is pointing; L is the unit vector pointing from
Q to the light position; and the exponent p controls the rate at which the intensity
falls off as the angle between R and
L increases.
Ambient and Diffuse Lighting
The ambient and diffuse contribution to the illumination color calculated at a
point Q on a surface is given by the expression
n
NL
{
}
=+
  
max
, 0
,
diffuse
i
i
i
=
1
where is the surface's diffuse reflection color, N is the normal vector to the
surface, L is the unit vector pointing from Q toward the i -th light, is the inten-
sity of the i -th light at the point Q , and represents the ambient light color.
Specular Lighting
The specular contribution to the illumination color calculated at a point Q on a
surface is given by the expression
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