Game Development Reference
This display of Surface Normals is showing us which direction
each polygon is facing. Notice that the red areas tend to be fac-
ing right, green areas tend to be pointing upwards, and blue areas
tend to be facing the camera. Areas that face a direction between
these have blended colors.
Here's the magic, folks. Because the polygons facing upwards
are green, and if we can extract that green data and remap it,
we can relight the scene. And, that's exactly what we're going
Duplicate this layer and delete the 3D Channel Extract effect
from the bottom copy only. On the top copy of this garage scene,
apply the Shift Channels effect. In the Shift Channels effect,
change the Take Red From, the Take Green From, and the Take
Blue From values to Green. This will create a grayscale result that
displays the amount of green light in the Surface Normals in this
scene. Note that the areas that appear the most green are white
(Fig. 5.65 ).
Figure 5.65 The Shift Channels
effect can create a grayscale
map that represents the amount
of green light in the Surface
Then, in the Timeline panel, place the top copy of the garage
layer into the Overlay blend mode. This will remove the gray
areas of the image, and brighten the areas that are white on the
top copy, which adds more light to the scene (Fig. 5.66).
To really see the power of what just happened, I'm going to
zoom in closer to the car, and do a split screen. What we did here
couldn't have been accomplished by another luminance adjust-
ing effect, because we just increased the lightness of the objects
pointing upwards. This isn't possible without 3D data. Even the
crevasses of the hubcaps that are pointing upwards have been
relit in a very natural way.