Adding new base frames

After Effects creates an initial Roto Brush span of 20 frames. As you move through the frames, the span range may increase automatically, or you can drag it to extend the span. However, the further you move from the base frame, the longer After Effects requires to propagate, or calculate, the segmentation for each frame. 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.

After you have reached 1:20 (1 second, 20 frames) in the refining process, add a new base frame to the project.

1 Go to 2:10 in the Layer panel. This frame isn’t included in the initial span, so the segmentation boundary disappears.

2 Use the Roto Brush tool to add foreground and background strokes, defining the segmentation boundary.

A new base frame (represented by a gold rectangle) is added to the time ruler, and the Roto Brush Span extends twenty frames behind and ahead of the new base frame.

3 If there is a gap between the initial span and the new span, click the left edge of the new span, and drag it back to the edge of the previous one.

4 Press 1 to move backward one frame (from the base frame) and refine the segmentation boundary.

5 Continue to move backward through the span, refining the segmentation boundary until you reach the beginning of the new span.

6 Move back to the base frame, and then press 2 to move forward, correcting the segmentation boundary in each frame as necessary.

7 When you reach 3:00, create a new base frame at 3:20, and repeat the process. Create an additional base frame at 5:00, refining the segmentation boundary in each frame in the footage.

8 Move the time marker to the beginning of the time ruler in the Layer panel, and then press 2 repeatedly to progress through the clip. If you notice any errors, correct them with the Roto Brush tool.

9 Choose File > Save to save your work so far.

_ Tip: You can create a RAM preview to identify any errors in the segmentation boundary. Keep in mind, though, that After Effects begins the propagation calculations again for each span. Depending on your system and the complexity of the project, a RAM preview may take a long time.

Дата добавления: 2014-11-20