Compositing with Nodes - Mastering Blender - page 688

Animating the Garbage Matte
Now that you've set up the curve and activated the add-on, you can animate the garbage matte to cover the ne-
cessary background throughout the entire clip. To do that, follow these steps:
1. Position the points so that the matte covers everything on the left side of the background. Advance to a
framejustbeforetheoutlineofthefigurebeginstointersectwiththepieceofhardwareyouwanttomatte
out, and position the curve's control points so that they separate the figure from the hardware, as shown
in Figure 9-62 .
2. Insert a keyframe for this curve shape by pressing the Insert button on the AnimAll panel, as shown in
Figure 9-63 .
3. Hold Shift while pressing the up-arrow key on your keyboard to advance 10 frames at a time. Each
time you advance, adjust the positions of the curve's control points so that the matte covers the back-
ground and follows the contours of the foreground figure in places where background garbage and the
figure intersect, as shown in Figure 9-64 . It's not necessary for the matte to follow the entire contour of
thefigure—it'sonlynecessarytodistinguishinthoseplaceswherethebackgroundgarbageoverlapswith
the figure. When the figure has filled the screen, your matte should be keyed completely out of the Cam-
era view.