Game Development Reference
the Use For Matte drop down to Red Channel. This will use the
grayscale values of the red channel only to create transparency.
The result is that there is much less of the glow around the light-
ning used here, which creates a tighter matte (Fig. 5.60).
Figure 5.60 The result of using
the red channel to control the
If you selected the Invert Matte checkbox, then the lightning
would cut a transparent hole in the lava layer. This lightning has
already been animated. If you preview this comp, you'll see that
this inverted matte is actually a traveling matte (Fig. 5.61).
Figure 5.61 Selecting the
Invert Matte checkbox creates
a lighting-shaped area of
transparency in the lava layer.