Game Development Reference
Figure 2.2 After applying
the 3D Channel Extract effect,
the image is changed to shades of
gray that represent the depth of
the 3D objects.
this layer. The layer is then turned to shades of gray. These shades
of gray represent the levels of depth in the 3D fi le (Fig. 2.2).
Using the default values, it's diffi cult to see what's going on
here. But these grayscale values are supposed to represent the
3D depth of each object, with the objects closest to the camera in
white and the objects furthest from the camera in black. But right
now, everything is just gray. Let's fi x that.
In the options for the 3D Channel Extract effect in the Effect
Controls panel, we have three options. First is the 3D Channel
drop down, which specifi es which channel from the 3D fi le to
extract. The default setting is Z-depth (i.e., 3D depth), and we'll
leave it here for a moment. Next we come to the Black Point and
White Point values, which determine the furthest and closest 3D
points in this image, respectively. The numbers represent the dis-
tance in pixels the 3D objects are from the virtual camera.
But how do we know how exactly how far away they are? The
answer is simple—use the Info panel. With the 3D Channel
Extract effect active and selected in the Effect Controls panel,
click on the spot where the table is on the right-hand side of the
image. This table is the object closest to the camera. Once you
click in this image in the Composition panel, its Z-depth infor-
mation will show up at the bottom of the Info panel (Fig. 2.3).
Now we know that we need to set the White Point value to
about −89. And although we don't have the shadow information
corrected yet, we have more contrast in our depth map (Fig. 2.4).
Next, let's repeat the same procedure, but we'll use the back-
ground this time. With the 3D Channel Extract effect still selected
in the Effect Controls panel, click on the darkest point of this