Following moving subjects

Doodles can follow a subject, like a star above a walking person's head or an arrow pointing at a rolling ball. Draw just one box and the whole video is tracked automatically.

Steps

1. Go to a frame where the subject is clearly visible.
2. Press Track box (T) and draw a box around the subject. Wait a moment while it tracks forward and backward through the video.
3. Select a doodle and, under Follow on the right, pick the track you just made (t1, etc.). The position shown right now becomes the reference, and the doodle keeps that offset as it follows.
4. To also scale the doodle as the subject gets closer or farther, turn on Scale too.

Drawing a good box

• Box a part with clear patterns or edges. Faces, logos and corners track better than the middle of a plain shirt.
• Fit it snugly so little background gets in. Too small, and it's easily lost.
• By default, tracking keeps the box size fixed and follows only the position. Scenes where the subject moves far closer or farther can drift more.

Fixing jumps

The color of the track stripe under the timeline shows its state.

1. Select the track and use Next problem ▶ to go to a red frame.
2. On that frame, drag the box back into place (resize from the bottom-right corner). That frame becomes 'set by hand'.
3. If Re-track automatically from fixed frames is on, it re-tracks from there to the next hand-set frame.

When the subject is hidden and reappears

When the subject passes behind something, tracking may wander off. Press I on the frame just before it's hidden and O on the frame where it reappears, then press Interpolate to join the stretch in between with a straight line.

Reducing jitter

Raising Reduce jitter averages the positions of neighboring frames to smooth the motion. Hand-set frames stay exactly as they are. Set too high, fast motion is followed with a lag.