Editors Guild by Ben Bardens
In the previous two installments in this series (Editors Guild Magazine MAR-APR 10, MAY-JUN 10), I covered time-tested and traditional techniques for rotoscoping footage using After Effects and Photoshop. These techniques, involving animated mask shapes or exporting frames to Photoshop, while fundamental and effective, require the user to determine the edge of the roto matte manually, and don’t really rely on the computer to assist with in-betweening matte shapes from frame-to-frame.
The result is that doing roto, even for a relatively simple clip, has always been a time-intensive and tedious task. Thanks to the new Roto Brush in Adobe After Effects CS5, roto artists now have a tool to use which features automatic edge detection and matte propagation, and can greatly reduce the amount of actual frame-by-frame work with which roto artists have to deal.
Users who are familiar with the Quick Selection tool available in recent versions of Photoshop will recognize the “context aware” behavior of the Roto Brush. Just like the Photoshop Quick Selection tool, it is not necessary to define the edge of your subject. You simply use the brush to define the area within the subject that you wish to keep, and then use the brush again to identify the areas that you wish to exclude. The context-aware technology works its magic, analyzing both color and shape, to automatically determine the edge of your matte––and does a remarkably good job at it. You can then control the range of frames that you wish the Roto Brush to analyze, and automatically generate the roto matte. read more...