As we mentioned in our last post, we’re going to be publishing on PVC videos from our retired Lynda.com course Insight Into Effects that we think are still relevant to users today. They use a much older version of After Effects, but it’s surprising how much of the program has stayed the same over the years. As a result, many tricks that were useful back then are still useful today. We’re going to focus on the “universal concepts” movies from that course first, and then move onto specific effects plug-ins.
This movie is about a mysterious switch that appears in some plug-ins: Repeat Edge Pixels. It’s useful when an effect has the option of blurring or otherwise extending a layer’s alpha channel, but there are no pixels beyond the original edge to process.
What should do you do in this event? Well, you either crop the alpha channel at its original boundaries rather than blur it, or you repeat the color of the pixels at the very edge so that you have something useful to process. Otherwise, After Effects may give the appearance of “pulling in” black pixels from the edge – but in reality, most of the time what you’re seeing is the black background.
Here’s that concept demonstrated, with some simple rules for when to enable or disable the Repeat Edge Pixels Option: