Game Development Reference
lightness channel. Huh? To understand this, let's take a look at
only the red channel of the original layer (Fig. 5.28).
By remapping the red channel to the lightness channel, we're
telling After Effects to control the lightness of this image using
these grayscale values (in the red channel). You can even use the
attributes of a second layer by enabling the Use Second Layer
option, and selecting a layer from the Source Layer drop down.
So what cool stuff can you do with this? To see some more
practical examples of this, hop over to the Darken/Change Color
comp. It contains another instance of the same comp, with the
3D garage scene and the Channel Combiner effect. But, the effect
has already been set up for us here. In this case, the From value is
set to the blue values in this image, and the To value is again set
to the lightness values. This is far more interesting because yellow
and blue are opposites. That means that the car is very dark in the
blue channel because not much blue light is needed to make a
yellow car. So, when we use the blue channel to control the light-
ness of the image, we get a very dark car. Turn on the visibility of
the Channel Combiner effect in the Darken/Change color comp
to see the results (Fig. 5.29).
This is a very unusual result. It would be very challenging to
recreate this with a luminance-adjusting effect, like Levels or
Curves, because of all the intricate highlights, refl ections, and
other details on this car. But, they have not been dimmed at all
in this case because it took a lot of blue light to make those bright
highlights as well, so they remain bright when the lightness is
Very little is changed besides the car, which is another impres-
sive aspect of this result. Areas that had lots of blue to begin with
Figure 5.28 The red channel of
the original layer.