There; now it looks like there are two balls in the shot instead of one. All
we used was Backdrop Only GI and no lights. The render took less than
5 seconds, which is quicker, if you can believe it, than an area light ren-
der, which took 13 seconds.
A More Complex Lighting Environment
Figure 24.21 is a photo of a typical sunny winter day in Vancouver. (Note
the magnificent North Shore Mountains freshly dusted with snow —
skiing just half an hour from the city core!)
Although this image is black and white, it demonstrates a lighting
environment with three discrete lighting sources. The primary source,
or key, is the sun. The two secondary, or fill, sources are the diffused
skylight and the bright reflection from the wooden roof deck in the fore
-
ground. We can approximate the angle of the sunlight not only by the
shadow terminator on the test ball but also by the direction of the shad
-
ows on the ground.
················Chapter 24: Identifying and Recreating Light Sources in a Plate
359
Figure 24.20
Recreating this lighting requires an understanding of the nature of each
of these light sources. So what do we know about them?
We know that our key source, the sun, is the brightest of the three,
produces the hardest shadows of the three, and is somewhere in the
amber range of color. We know from our environment that this is a win-
ter scene. We know that it’s in the Northern Hemisphere above the 49th
parallel, so the sun is fairly low in the sky. The length of the shadows on
the ground confirms this. We know the mountains in the image are to
the north of the city (hence “North Shore”); therefore the sun is in the
west, indicating an afternoon timeframe. We know that the sky, one of
our two fill sources, is very large and therefore creates very soft shad
-
ows. We know that the sky’s color is somewhere in the blue range of the
color spectrum. The second fill, the light that is being reflected off the
wooden roof deck (this light is also known as a “bounce” light), is proba
-
bly a light grayish or brownish color. It is also a fairly large diffused light
source, although not nearly as large as the sky.
Part III: Creating Lighting ··································
360
Figure 24.21
My first inclination is to use a distant light for the sun, even though
the shadows will not be perfectly accurate, and two area lights, one for
the sky fill and one for the bounce light. The sky fill light will be consid
-
erably larger than the bounce light.
Now there are a number of different ways I could approach this
lighting problem using any number of lights and any number of combina
-
tions. There are methods that will render more quickly and there are
methods that will render more slowly. (Believe me, there are always
methods that will render more slowly!) I have selected this method as
being a sort of “middle-of-the-road” solution. Quality is likely to be fairly
high without monstrous render times.
First, let’s take some object and throw it into the scene. Then load
up the background image as we have done in previous sections. This
image is called Vancouver.tga and can be found on the companion CD.
I’ve decided to throw an old Egyptian monolith into the scene. Never
mind what an old Egyptian monolith is doing on a roof deck in Vancouver
in the middle of winter.
················Chapter 24: Identifying and Recreating Light Sources in a Plate
361
Figure 24.22

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