The Roto Brush is a revolutionary new approach in After Effects CS5 for Isolating moving foreground elements from their backgrounds. It is largely based on the Video SnapCut system, a research prototype that was jointly developed by Adobe and University of Minnesota, and was presented at SIGGRAPH 2009. Roto Brush works much like the Quick Select tool in Photoshop: you draw foreground and background strokes on key frames to make an initial selection, and the system automatically propagates the selection to other frames, which provides a fast workflow for generating masks in video.
Here are some links to learn this feature:
- Rotoscope with Roto Brush in After Effects CS5
- Refining a matte created with Roto Brush
- Roto Brush overview and workflow – Lynda.com