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Intensity/Color/Attenuation Parameters 1347
Inter face
Multiplier—Amplifies the power of the light by a
positive or negative amount. For example, if you
set the multiplier (page 3–977) to 2, the light will
be twice as bright. Multipliers are also usef ul for
subtracting light and selectively placing dark areas
in the scene. Default=1.0.
Using this parameter to increase intensit y can
cause colors to appear "burned out." It can also
generate colors not usable in videos. In general,
leave Multiplier set to its default of 1.0 except for
special effects and special cases.
High Mu ltiplier va lues wash out colors. For
example, if you set a spotlight to be red but then
increase its Multiplier to 10, the light is w hite in the
hotspot and red only in the falloff area, where the
Multiplier isn’t applied.
Negative Multiplier values result in "dark lig ht."
That is, the light darkens objects instead of
illuminating them.
Co lor Swat c h—Shows the color of the light.
Clicking the color swatch displays the Color
Selector (page 1–161) so you can choose a color
for the light.
Decay group
Decay is an additional way to make a light’s
int ensity reduce over distance.
Ty pe—Setsthetypeofdecaytouse. Thereare
three types to choose from.
•
None—(The default.) Applies no decay. The
light maintains full streng th from its source to
infinity, unless you turn on far attenuation.
•
Inver se—Applies inverse decay. The formula is
luminance=R
0
/R, where R
0
is the radial source
of the light if no attenuation is used, or the Near
End value of the lig ht if attenuation is used. R
is the radial distance of the illuminated surface
from R
0.
• Inver se Square—Applies inverse-square decay .
The formula for this is (R
0
/R)
2
.Thisisactually
the "real-world" decay of light, but you might
find it too dim in the world of computer
graphics.
This is the decay formula used by photometric
lights (page 2–1301).
Tip: IfInverseSquaredecaymakesthescenetoo
dim, you can try using the Environment Panel
(page 3–272) to increase the Global Lighting
Level value.
The point at which decay begins depends on
whetherornotyouuseattenuation:
• With no attenuation, decay begins at the source
of the light.
• With near attenuation, the decay beg ins at the
Near End position.
Once the beginning point is established, the decay
follows its formula to infinity, or until the light
itself is cut off by the Far End distance. In other
words, the distance between Near End and Far E nd
doesnotscale,orotherwiseaffect,theapparent
ramp of decay ing light.