Interior or Exterior
Perhaps one of the first decisions you will have to make about your light
ing is whether it is an interior or exterior shot. This is a basic and
general question that will provide you with a great deal of information
about your lighting setup. The shot might contain both interior and exte
rior elements, such as a room interior with a window through which the
street outside is visible. Or it might be an exterior shot that includes
someone leaning out a window and waving. There is interior lighting
behind that person. It may be subtle, but illuminating that interior prop
erly might make the difference between a shot that is believable to the
audience and one that is not. Or it may be nighttime and the light in the
window is spilling out into the yard. The question is whether the camera
is inside a building or out on the street. Interior and exterior light
sources may both play a part in the shot, but the location of the camera
(the shot) dramatically changes how the sources will be handled and
what the relative light intensities will be between interior and exterior.
Part I: Lighting Theory ···································
Figure 2.1: An interior image. Note lighting
sources and intensity.
Interior and exterior light react and complement each other all the time,
everywhere. Knowing how to create these complex interactions is as
simple as identifying and simulating each individual source.
Interior light sources, for example, are usually incandescent
lightbulbs, flames, or fluorescent lights. Exterior light sources are usu-
ally the sun, the sky, clouds, the moon, reflected sources, and reflected
diffuse sources (technically, all these sources are the sun, but let’s not
wear our picky hats today). Some of the sun’s light, diffused through the
air molecules in the sky, creates a global, diffused source. Or the sun
may be occluded by clouds that block the direct rays from the sun, in
which case the light is diffused among the water droplets in the clouds,
creating yet another diffuse source. Direct sunlight may strike a wall or
the ground, picking up the color of that wall or ground and reflecting it
onto another surface. In CG, we call this light bounce or reflection
radiosity. (Don’t get all nitpicky about the actual physics of light reflec
tion and radiosity yet. We’ll discuss all that later.) Sunlight may reflect off
the surface of a swimming pool, creating a hard reflection against the
pool house. In each circumstance, the sun is the light source. All the
other lighting events, with the exception of artificial light, are diffusions
or reflections of that primary source.
While it is theoretically possible to create a global lighting environ
ment with only one source and to provide diffusion and reflection events
consistent with the real world, render times would probably be
······························Chapter 2: What, Where, When?
Figure 2.2: An exterior image. Also note light sources, intensity, and

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