Adobe After Effects - Manual (Page 395)

Roto Brush and Refine Matte | CS6
Note:
To the top
To the top
Online resources for the Roto Brush tool and Refine Matte effect
Roto Brush and Refine Matte overview and workflow
Tips for working with the Roto Brush tool
Roto Brush strokes, spans, and base frames
Roto Brush effect and Refine Matte effect reference
Freezing (caching, locking, and saving) Roto Brush segmentation
Layer panel view options
Separating a foreground object, such as an actor, from a background is a crucial step in many visual effects and compositing workflows. When
you’ve created a matte that isolates an object, you can replace the background, selectively apply effects to the foreground, and much more.
Conventionally, segmentation of a moving image into foreground and background elements has been accomplished through rotoscoping—defining
mattes by manually drawing Bezier curves (masks) on most frames, with some interpolation. (See Rotoscoping introduction and resources.)
The Roto Brush tool provides an alternative, faster workflow for this segmentation and creation of a matte.
With the Roto Brush tool, you draw strokes on representative areas of the foreground and background elements, and then After Effects uses that
information to create a segmentation boundary between the foreground and background elements. The strokes that you make on one area inform
After Effects about what is foreground and what is background in adjacent areas and on adjacent frames. Various techniques are used to track
regions across time, and this information is used to propagate segmentation forward and backward in time so that each stroke that you make is
used to improve the results on nearby frames. Even if an object moves or changes shape from one frame to the next, the segmentation boundary
adapts to match the object.
After you have created a segmentation boundary, you use the Refine Matte properties to improve the matte. The Refine Matte effect is also
available separately for the improvement of mattes created using features other than the Roto Brush tool.
After Effects CC includes enhancements to make rotoscopy easier. See Roto Brush and Refine Edge tools in After Effects CC.
Online resources for the Roto Brush tool and Refine Matte effect
For a collection of video tutorials and resources about the Roto Brush tool, see this article on the Adobe website .
For a video that demonstrates the use of the Roto Brush tool to quickly create a matte for selective color correction, see the Adobe website .
For a video that demonstrates the use of the Refine Matte properties in the Roto Brush effect to improve a matte, see the Adobe website .
John Dickinson provides a video tutorial on the Motionworks website that demonstrates the Roto Brush tool.
Chris & Trish Meyer share tips on the Roto Brush tool on the ProVideo Coalition website .
Roto Brush and Refine Matte overview and workflow
1. Activate the Roto Brush tool by pressing Alt+W (Windows) or Option+W (Mac OS).
2. Open the layer that you want to work on in the Layer panel.
note: Double-clicking a layer in the Timeline panel when the Roto Brush tool is active opens the layer in the Layer panel.
3. Preview the movie in the Layer panel to find a frame in which the greatest amount of the foreground object is in the frame and in which the
separation between the foreground and background is as clear as possible.
The frame on which you draw your first stroke is the base frame. (See Roto Brush strokes, spans, and base frames .)
391