5. Use the Roto Brush tool to add to the foreground or subtract from the background as
necessary to refine the boundary.
6. Repeat steps 4 and 5 until you reach 1:00.Adding new base frames
After Effects creates an initial Roto Brush span of 40 frames (20 in each direction). As you move
through the frames, the span range may increase automatically, or you can drag to extend the
span. However, the further you move from the base frame, the longer After Effects takes to
propagate, or calculate, the segmentation for each frame, especially if the shot is complex. If the
scene changes significantly, it may be better to create multiple base frames for your footage than
to have one really long span. The scene in this project remains fairly consistent, so you could
extend the span and make additional adjustments as needed. However, you’ll create additional
base frames to gain experience using the tools, learn to connect spans, and see how the
segmentation shifts as you move further from a base frame.
You’ve reached 1:00 in the refining process. Now you’ll add a new base frame to the project.
1. Go to 1:20 in the Layer panel. This frame isn’t included in the initial span, so the
segmentation boundary includes the entire frame.
2. Use the Roto Brush tool to add foreground and background strokes, defining the
segmentation boundary.