Further, it is crucial that you understand the textures and materials
that you are lighting. You need to know the properties of those textures.
Are they highly specular or matte in finish? Should they be highly reflec
tive or glossy? Understanding how the textures should be reacting to
your lights is a big indicator as to whether or not your lighting is appro
priate or your textures are appropriate. If one or the other is too far off,
either the element will be unsuccessful or the compositing artist will
have a great deal of work to do to make it a success. As a lighting artist,
you should take pride in providing lighting and shading that requires lit
tle compositing alteration. If nothing else, this makes you a valuable
asset because you are saving your company money in compositing time.
About Plates and Light Sources
A plate describes the photographic element (either a still or an image
sequence) onto which we want to add some sort of computer-generated
element. Take, for example, the dinosaurs in the movie Jurassic Park.
The dinosaurs themselves, of course, were CG, but the background
plates were filmed. This is what we mean when we talk about
compositing a CG element onto a plate or background plate.
Now, how do we identify light sources? And how do we recreate
them for CG elements that will be added to the plate?
First, learn how to look at light and shadow. Understand the quali-
ties and properties of light. Know the color temperature, angle, size, and
everything else about every light source. It is very helpful to understand
the types of luminaries, or lighting instruments, gels, flags, and diffusion
filters used by the lighting crew on set. Second, learn how to use the
tools in LightWave. Know how to make a hard shadow and a soft one.
Understand inverse square falloff and how to create real soft shadows
and everything else there is to know about the lighting tools in
LightWave. Part II of this book and the LightWave manual both deal
extensively with how to use the toolset.
Probably the very easiest way to learn how to match CG lighting to
a plate is simply to look at some photographs, identify the light sources,
then proceed to set them up in LightWave, compositing the two at the
end. In this chapter we will look at a few different lighting scenarios.
After you have lit a few hundred CG elements to match plates, you
will probably get a feel for the lighting just by looking at any old photo.
But to begin, it may be beneficial to look at a couple of tools that can
help you identify light sources, their direction, and other properties. Per
haps the most used lighting analysis tool is a matte ball. Just any old
Styrofoam ball will do, although it should probably be at least 12" across
Part III: Creating Lighting ··································
to give you a good look at the lighting. Some prefer to use a gray ball. In
this case, I managed to get my hands on an 18% gray ball used in a fea
ture film and also a mirror ball (no, not the kind used in discos and high
school dances), which we will discuss later.
If you need to light CG elements to a plate and you are lucky enough
to have someone on set who will stick a ball in the shot and shoot a few
frames in exactly the same lighting context, your life will be made easier.
Rather than guessing at what the lighting might be, you will have a
better visual reference. Of course, a well-organized shoot will include
several feet of film containing nothing but the clean plate (empty set
with no performers) and a gray or mirror ball. If the footage is shot
through the same camera that is used to shoot the film, you’ll be that
much more likely to accurately match the lighting. Below is an image of
a gray ball in a studio setting.
In this context, the direction and relative intensity of the key lighting
source is completely obvious. We can see by the shadow on the ball that
there is one key light source and that it is above the ball to the left and
slightly closer to the camera than the ball. If the light source were
behind the ball, more than half the ball would be in shadow. But more
than half the ball is in the light, so we know that the light source is
closer to the camera than the ball is, thereby illuminating more of the
ball facing the camera.
Take a look at the next image and see if you can clearly identify the
················Chapter 24: Identifying and Recreating Light Sources in a Plate