came to mind in a moment. There are infinite other combinations that
you can use to create a lighting environment that is true to the setting,
conveys the mood you wish, and carries the desired emotional impact.
Size matters.
The size of a light source, like most of the other properties, often
will not matter in shots, but can occasionally be crucial to lending reality
to your lighting environment. What difference does size make? Mainly
the difference is in the shadows. Shadow shape and behavior will vary
depending on the size of the light source. A very large but distant source
like the sun will result in hard shadows near the object and softer shad
ows farther away. A very small light source such as a light-emitting
diode will result in very hard shadows that only become soft very far
away, if the light transmits that far. A large light source like the sky or
clouds will result in very soft shadows, usually beneath objects. The net
effect is that tiny light sources appear to result exclusively in hard shad-
ows, while very large light sources like the sky, computer monitors, or
large neon signs appear to create only very soft shadows. They don’t, in
fact, but they appear to do so. Remember that all shadows are sharp (or
in focus) at the point where the object casting the shadow touches the
object receiving the shadow, and soften more the farther away the
shadow is from the object casting it.
································Chapter 1: Properties of Light
Figure 1.16: An area light has been used in all three images to demonstrate the varying
size of a light source. The rendered images below them show the corresponding result of
each size difference. Nothing is changed except the size of the area light. A very small area
light acts as though it were a point source. This image uses a grid size of 1 meter.
On the other hand, a very small light source is more likely to result in
small areas of highlight on specular surfaces, while very large lights are
more diffused and are therefore less likely to result in small, bright spec
ular highlights. This is because, in CG, larger lights distribute their light
intensity over a larger area than small lights do.
This chapter has demonstrated the basic properties of light. The physi
cists among you will, no doubt, care to argue the physical accuracy of
several points; however, this is not a physics handbook. The understand
ing of the properties as described will enable you to light your scenes so
they appear to obey the laws of physics (which is very important) with
out actually having to obey every principle and law (which is not very
The final render matters. Whether or not you obeyed the letter of
physical law does not.
You should now be able to examine any lighting environment and
define the properties of intensity, color, direction, diffuseness, shadow,
shape, contrast, movement, and size. I urge you to examine each part of
this chapter, then examine real lights and real shadows. Try to discover,
for yourself, whether or not nature bears out what this chapter discusses
about light and shadow.
Part I: Lighting Theory ···································

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