Game Development Reference
Using Alpha Channels with Advanced Lightning
You can use alpha channels with the Advanced Lightning effect
to contain lightning within a layer, or to exclude the lightning and
have it strike around the alpha. This is one of the most powerful
features of the Advanced Lighting effect. If you wish to go along
with me, open the comp Logo Lightning-Start. This contains a
logo I created in Adobe Illustrator. Apply the Advanced Lightning
effect to the Arrows layer (Fig. 9.8).
Figure 9.8 The Logo Lightning-
When you fi rst apply the effect, the Arrows layer disappears. To
make it visible with the lightning, select Composite on Original.
What we're going to do here is to fi ll the Arrows layer with lightning,
but only where there are pixels already. To make our lightning more
visible, I'm going to take the Lightning Type value to Bouncey.
Then, all you have to do is adjust the Alpha Obstacle value.
That's it! Move the Alpha Obstacle value to a negative number to
force the lightning to stay within the confi nes of the arrows. You'll
also want to make sure that the Origin point is located on one of
the arrows, for best results. To get mine looking correctly, I had to
reduce the Glow Radius a bit. I also reduced the Core Radius and
Forking values a little (Fig. 9.9).