point light will work fine, but sometimes you will find you need the
accuracy of radiosity lighting.
Note: Either Monte Carlo or Interpolated radiosity must be
enabled for this to work. Luminous surfaces will not emit light into
the scene if you have Backdrop Only radiosity selected.
Intensity or luminosity is one of the first things you may notice about a
light source’s quality. Is it very bright or very dim? Is it somewhere in
the middle? Is it so blindingly bright that it can only be the sun or a
nuclear blast? Or is it so gentle that it must be a candle or a firefly? The
intensity of a light source will often signal to the viewer what the light
source is, even if the source itself is not visible in frame.
Note: It is easy to let the audience know what and where your
light source is without being obtrusive or obvious. As you read
through these light properties, imagine how you might use each
one to let your audience know just how the scene is illuminated.
Color
Perhaps the second quality you may notice in a light source is the color.
Take the sun, for example. On a midsummer’s day, the sun can be very
close to white and slightly on the yellowish (amber) side. On an autumn
afternoon, it can be a fiery orange. Look in the shadows on a clear, bright
sunny day. Don’t they look blue? They are. Do you know why? What
about the living room with the fireplace burning? Here you see orange,
red, and yellow all spilling across the room. Or check out those mercury
vapor lamps used for streetlights. The light emitted from these is a light
orange.
Take a look at Figure 1.3.
There are three main light sources in this shot, resulting in three
distinct color ranges. In a few places, you can see direct sunlight, mainly
along the top of the image and at the bottom right. The sun is the key
light. It is nearly white, on the amber side of the spectrum. But the most
obvious light sources and colors are the fill sources. On the left of the
image, rock faces that angle upward are a deep blue. This is because
they are facing the blue sky on a bright, sunny day. The sky is highly
luminous and is emitting a blue-tinted diffuse light. On the right half of
································Chapter 1: Properties of Light
5
the image, the cliff face is undercut, making it face downward toward the
road where sunlight is reflecting off the dirt and creating an amber fill.
Note: This image is a great example not only of contrasting
color in a lighting environment, but also of fill lighting, bounce
lighting, and diffuse lighting sources.
Note: After the first edition of this book was released, there
was heated debate over the color of shadows on a sunny, clear,
blue-skied day. Some argue that shadows have no color, being by
nature the absence of light. On the other hand, it can be argued
that on earth shadows are never completely devoid of light. I sup
-
pose for the picky physicists in the room, the question should be
“What color of illumination fills the shadowed area?” I won’t
address the doubt, incredulity, debates, insults, or downright crying
that was involved, and I stand by my analysis of the lighting condi
-
tions. I urge you, incredulous reader, to simply go outside and do
some careful, thoughtful observation. Come to your own
conclusions.
There are as many colors for lights as there are colors in the visible
spectrum. In fact, you can divide up the visible spectrum of light into
many more wavelengths than can be discerned by the human eye. Your
computer monitor is probably capable of displaying about 16 million col
-
ors, and that’s only some of the available ones!
Part I: Lighting Theory ···································
6
Figure 1.3 (See color image.)

Get LightWave v9 Lighting (w/CD) now with O’Reilly online learning.

O’Reilly members experience live online training, plus books, videos, and digital content from 200+ publishers.