2009

increases, attenuation is in effect, or if the light has a color, the surface
intensity can be reduced.
In other words, the position and orientation of the light, relative to the object,
are what control the angle of incidence in a scene. The
Place Highlight
command
on page 1018 is one way to fine-tune the location of a light.
Attenuation
For standard lights,
attenuation on page 7915 is turned off by default. To shade
or render a scene with attenuation, you turn it on for one or more lights. All
types of standard lights support attenuation. You can set explicitly where
attenuation begins and where it ends. This is partly so you don’t have to worry
about setting up strictly realistic distances between light objects and the objects
they illuminate. More importantly, this feature lets you fine-tune the effect
of attenuation.
In outdoor scenes, attenuation can enhance the effect of distance. (Another
way to model environmental effects is to use the atmospheric settings when
you render. See
Environment and Atmosphere Effects on page 6687.) In an
indoor setting, attenuation is useful for low-intensity light sources such as
candles.
Photometric lights always attenuate, using an inverse-square falloff, as in
nature. (In the case of the IES Sun Light, its great intensity makes its
attenuation hardly apparent.)
Reflected Light and Ambient Light
Rendering with the default renderer and standard lights does not calculate
the effect of lights reflected from objects in the scene. Because of this, lighting
a scene with standard lights often requires you to add more light objects than
would be needed in real life. You can, however, use
radiosity on page 6168 to
show the results of reflected light.
When you do not use a radiosity solution, you can use the Environment panel
on page 6689 to adjust the color and intensity of ambient light. Ambient light
affects contrast. The higher the intensity of ambient light, the lower the
contrast in the scene. The color of ambient light tints the scene. Sometimes
ambient light is bounced light that gets its color from other objects in the
scene. Most of the time, however, the color of ambient light should be the
complement of the color of the principal light source for the scene.
Using Lights | 4985