Chris Meyer |
Thursday, April 11, 2013
Refine Edge: A new way to deal with hair
As you no doubt know by now, Adobe has started to reveal some plans for its next generation of pro video tools. I’ve had the privilege of working with a pre-release version of Adobe After Effects, and recorded two hours of lynda.com training about it. In this blog, I’ll give you an overview of the Refine Edge tool, an important addition to the Roto Brush technology that will make rotoscoping hair and other soft, detailed areas much easier than ever before.
Roto Brush and Refine Edge
The Roto Brush tool in After Effects has been significantly upgraded with the addition of a companion Refine Edge tool. To review, Roto Brush allows you to make a series of general paint strokes defining the foreground and background areas of an image (such as an actor over a complex background—in other words, not green screen). With this information, as well as judicious tweaking of its propagation parameters, Roto Brush then detects the edge between the foreground and background, and creates a matte. When used properly (as demonstrated in my course After Effects Apprentice 13: Paint, Roto, and Puppet), it can greatly reduce the labor involved in cutting elements out of video.
After the Roto Brush module has been used to create a good binary matte, the Refine Edge module then goes after those nuanced areas of partial transparency—such as fine, wispy hair. Using the same brushstroke paradigm as Roto Brush, you create Refine Edge brushstrokes to indicate where the areas of partial transparency are, as well as help define tricky areas that should be fully transparent or opaque. These refine strokes track along with the matte edge created by Roto Brush, greatly reducing the number of corrective strokes you need to make.
Below is a sequence that shows the original shot, the user interface to define the area to be refined, and the resulting alpha channel:
During the course of this shot, the model turns her head, causing her hair to fly about. This would normally be near impossible to mask, and difficult to key even if she was shot on a green-screen stage.
(credit: clip #10076482 courtesy iStockphoto/Milax)
After Roto Brush has been used to create a general binary matte (the pink outline still visible on her arms), the Refine Edge brush is then used to define areas of partial transparency. The result of these strokes is shown as an “X-ray view” that reveals the alpha channel in this region. The foreground is still in color; the background is in black-and-white, but not dropped out altogether so you can spot stray strands of hair during this stage.
The resulting alpha channel after a little tweaking of the Refine Edge Matte parameters to get better contrast and more definition in the flyaway hair.
Although hair is the obvious use for Refine Edge, it can help with any partially transparent edge. Indeed, it has a companion effect called Refine Soft Matte (which has the Roto Brush section removed) that can be applied to already masked or keyed footage. I’ve found it does wonders restoring heavily motion-blurred areas after keying.
Some tools save you hours. Refine Edge crosses that line toward allowing you to tackle shots you would have given up on otherwise. No, it’s not completely automated and foolproof; you will have to spend a little time mastering it (and that’s where I hope my videos prove useful for you), and using it properly. But once you do, the time involved in rotoscoping hair will drop to minutes versus hours, or tens of minutes versus “not in your lifetime.”
For a demonstration of Refine Edge in action, please see my new course After Effects Technology Preview. In my next blog, I’ll move on to the visual effects tools Warp Stabilizer VFX and 3D Camera Tracker.
Interested in more?
• Start a free trial membership at lynda.com
• The full After Effects Technology Preview series
• Courses by Chris Meyer on lynda.com
• All lynda.com After Effects courses
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Tags: Adobe after effects, After Effects, Rotoscoping, Video
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