8

286 Chapter 18: Effects and Environments
Lights group
Pick Light—Click the light that you want to enable
for volume light in any viewport.
You can pick multiple lights. Click Pick Light and
then press H.ThisdisplaysaPickObjectdialog
that lets you choose multiple lights from the list.
Remove Light—Deletes a light f rom the list.
Volume group
Fog Colo r—Sets the color for the fog that makes up
the volume of the light. Click the color swatch,
and then choose the color you want in the
Color
Selector (page 1–157)
.
You can animate the color effect by changing the
fog color at a nonzero frame with the Auto Key
button on.
Unlike the other fog effects, this fog color combines
w ith the color of the light. Possibly the b e st effec t
is to use white fog and then color it with a colored
light.
Attenuation Color—Attenuates volume light over
distance. The volume light ramps from the Fog
Color to the Attenuation color over the light’s Near
and Far attenuation distances. Clicking the color
swatch displays a color selector so you can change
the attenuation color.
Attenuation Color interac ts with Fog Color.
Forexample,ifyourfogcolorisredandyour
attenuation color is green, in the rendering your
fog will shade to purple. Typically the attenuation
color should be very dark and neutral—black is
agoodchoice.
Use Attenuation Color—Makes attenuation color
active.
Exponential—Increases density exponentially w ith
distance. When turned off, density increases
linearly with distance. Activate this check box only
when you want to render transparent objects in
volume fog.
Density —Sets t he density of the fog. The denser
the fog, the more the light reflects off it inside the
volume. Densities of 2 to 6 percent probably m ake
the most realistic fog volumes.
Left: Original scene
Right: Increasing the density
Max Light% —Represents the maximum glow effect
that you can achieve (defaults to 90 percent). By
turningthisdown,youcanlimitthebrightnessof
the glow so that it doesn’t get denser and denser as
it gets farther away from the light and "whites out."
Note: When your scene includes transparent
objects inside a volume light, set Max Light to 100
percent.
Min Light% —Similar to an ambient light (page
3–1002)
setting. If Min Light% is greater than 0,
areas outside the light volume will glow also. Note
that this means areas of open space (w here the
lightraycantravelforever)willendupthesameas
the fog color (just as with normal fog).
Without objects behind the fog, the scene will
always be as brig ht as the fog color if the Min
Light% is greater than 0 (no matter what the actual
value is). This is because the fog goes to infinit y
and is accumulated infinitely. If you’re going to use
min light% values greater than 0, you should make
sure that you enclose your scene by geometry .
Atten. Mult. (Attenuat ion Mu ltipl ier)—Adjusts the
effect of the attenuation color.