Advanced Compositing Features - The Focal Easy Guide to After Effects - page 204

Channels - paint on the Color, Alpha, or both channels.

Duration - methods of how the Paint Brush records your action over time,
with several operating options:

- Constant - the stroke appears always

- Write On - the stroke is recorded as you draw,

then can be played back at any reveal rate you
wish (forward or reverse)

- Single Frame - you manually advance the clip to each frame you need

to draw upon

- Custom - sets how often the clip advances with each stroke.

The Write On process is very simple and will make you smile:
1

Begin with a New Comp (Ctrl N) titled Right On! at 640 360 at

24 fps.

2

Create a Solid white layer, then double-click on it to open in the Layer
Window.

3

Select a Brush Tip that's solid and size 19.

4

Set the Duration to 'Write On'.

5

With the CTI at frame 0, draw a big circle in the center of the Layer
Window's screen.

6

Select the White Solid layer and press the 'U' key to open the layer's

Paint Brush 1 Stroke Options animated Keyframes.

When you finish the circle it disappears. This is because the CTI is still located
at frame 0 of the Timeline. Scrub the CTI to view the circle as it animates on.
7

Set the CTI to the last Keyframe of the circle 'Brush 1' stroke.

8

With the 'Brush 1' stroke not selected, draw a smile inside the circle.