The Auto-trace feature in Adobe® After Effects® 6.0 gives you the ability to create one or more masks from the outlines of an alpha channel. Applying the new Scribble effect (similar to the Adobe Illustrator® Scribble Fill effect) to the mask provides endless possiblities for creative animations.

1. Import a footage file that includes an alpha channel.

Import a still-image file or a motion-footage file that contains an alpha channel. Auto-trace creates separate masks for each area of transparency, so try to avoid using footage with several separate areas of transparency, such as a line of text, as it could require several minutes to process.

Add the footage to a composition.

2. Apply Auto-trace.

Next, create masks using the alpha channel of your layer by selecting the layer in the Composition window or Timeline window and choosing Layer > Auto-trace.

In the Auto-trace dialog box, select Work Area to create masks for the duration of the layer, and choose Alpha from the Channel menu. (While you can create masks using the luminance channel, it’s best to use Luminance with high-contrast, black-and-white images only.)

If you want the resulting masks to tightly conform to the contours of the opaque areas of the layer, keep the Tolerance value low—high values result in angular masks. Changing the Threshold value has a subtler effect and shifts the mask vertexes only slightly. Blur helps to combine masks for a discontiguous alpha channel. If you want to create masks that outline transparent rather than opaque areas, select Invert. Or, to create masks on a different layer than your original image, select Apply to New Layer. Leave the other options at their default settings and click OK.

3. Adjust masks as needed.

Auto-trace creates one or more masks on your footage or on a new layer. If the masks don’t outline your image as closely as you’d like, choose Edit > Undo and reapply Auto-trace, adjusting the Tolerance, Threshold, or Blur settings.

5. Apply the Scribble effect to the mask layer.

Open the Effects palette and type Scribble in the Contains text box.When the icon for the Scribble effect appears, drag it to the auto-traced layer in the Timeline window. Or, if your layer is already selected, just double-click the effect to apply it.

5. Adjust the Scribble effect controls.

After you apply the Scribble effect to the layer, the Effect Controls window opens, displaying the Scribble effect controls. Here you choose the angle, color, and style of Scribble you’d like to add to the mask.

Choose a mask option from the Scribble control that best suits your auto-traced image. Adjust controls by dragging the underlined value. To create fun, loopy lines, increase the Curviness value in the Stroke Options controls.

To animate the Scribble effect, set the Wiggle control to Curvy.

6. Preview the final result.

In the Time Controls palette, click the RAM preview button. (If the Time Controls palette isn’t available, open it by choosing Window > Time Controls.) Even though you didn’t set any keyframes for the effect, After Effects animates the Scribble effect because you selected a Wiggle control that randomly varies the effect over time.

7. Save the effect as a Favorite.

If you like your final results, you can save these Scribble effect settings as a Favorite effect and reuse them in other projects. Each saved effect appears in the *Favorites category of the Effect palette so that you can use it in other After Effects sessions or projects.

You can reference a single frame as your clone source or set the clone source to advance in time. You can paint the same pixels each time you click the mouse or you can paint more of the source frame. And, you are not limited to painting in the same layer once you’ve set your source point, you can paint any other layer in a composition.

1. Import a motion footage file.

In a new project file, import a motion footage file. You can use any movie file or sequence of still images that After Effects supports. Drag the footage file to the Composition icon in the Project window to create a new composition with same dimensions and duration as the file.

2. Apply the clone stamp tool.

In the Composition window, double-click the footage to open it in the Layer window, which appears as a new tab in the Composition window. Select Auto Open Palettes, and then select the clone stamp tool in the Tools palette.

3. Choose a brush tip.

When Auto Open Palettes is selected in the Tools palette, the Brush Tips palette and the Paint palette appear. You can use any preset brush tip with the clone stamp tool or create your own tip by adjusting and saving the brush tip properties. To change the brush values, drag the underlined value. You can resize your brush tip as you draw by pressing Ctrl (Windows) or Command (Mac OS).

The Paint palette contains two options that are specifically for use with the clone stamp tool. For now, make sure that both options are deselected. Choose Constant from the Duration menu so that each clone stroke appears on all subsequent frames.

4. Set your clone source point.

To find an interesting element, drag the current time-indicator in the Layer window. Place your cursor over the element and Alt-click (Windows) or Option-click (Mac OS) to set the clone source point.

5. Paint a clone stroke on a video frame.

Advance the footage to a frame where you want to paint the pixels you just sampled. Then, drag in the Layer window to paint in the layer using sampled pixels from the source frame. Release the mouse, move the cursor a short distance away, and drag again to paint more of the original sample. Each stroke paints on the pixels from the source point.

(After Effects sets the duration between your clone source point and your initial stroke in the Time Shift value. When you advance the frame from your initial stroke, painted pixels change to reflect subsequent source frames. To prevent strokes from changing over time, use the Lock Source Frame option.)

6. Align your strokes.

Next, paint aligned clone strokes. Select Aligned in the Paint palette, and then locate a new area of interest in your footage and Alt-click (Windows) or Option-click (Mac OS) to set the clone source point.

7. Paint aligned clone strokes.

Advance the footage to the frame you want to paint. When you first drag in the layer, you paint on pixels from the location where you set your clone source point. However, as you release and drag in new locations of the frame, you paint on more of the source point frame rather than painting the same source pixels. If you continue to paint without releasing the mouse, you will eventually reproduce the entire source frame. In the example below, the clouds from the source frame are painted into other locations of the frame using aligned clone strokes.

You can achieve similar results with graphic images by using the clone stamp tool in Photoshop. After Effects and Photoshop provide additional cloning options, such as blending modes. For more information about the clone stamp tool, see After Effects online Help.

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1. Import an audio file.

In a new project, import an audio source file, such as a WAV, MP3, AIF or MOV file. Since you’re using the audio’s amplitude to animate the layer, music with a good beat works best, though any audio file will do. Create a new composition and limit the duration to a few seconds to speed up processing and previewing times. Add the audio file to the Timeline window.

2. Convert audio to keyframes.

Select the audio layer and choose Animation > Keyframe Assistant > Convert Audio to Keyframes. A new null layer called Audio Amplitude appears in the Timeline window with keyframes that contain values for the audio’s amplitude. To view these keyframes, select the Audio Amplitude layer in the Timeline window and press the U key on your keyboard. Leave the layer expanded.

3. Create a text layer to animate.

While you could use any type of source footage, text layers illustrate the capabilities of audio amplitude keyframes exceptionally well. Select the text tool in the Tools palette and click in the Composition window to create a new text layer. In the Character palette, choose a font and a font size that’s suitable for the size of your composition. (The composition shown has a 320 x 240 frame size and uses a 48 pixel font.) Leave the remaining controls at their default settings. Click in the Composition window and type a single word. Use the selection tool to reposition the text layer as needed.

4. Add an expression to the text layer.

The text layer includes several properties that you can animate with audio keyframes. To animate the size and color of the text layer, add an expression to the text layer’s Scale property. Later you’ll add an expression to the Hue property.

Expressions let you animate effects and properties by using mathematical variables, or by linking keyframes between layers with the pick whip.

Select the text layer and press the S key to reveal the layer’s Scale property. Then, select the Scale property and choose Animation > Add Expression. Drag the expression’s pick whip to the Both Channels slider for the Audio Amplitude layer.

5. Preview the animated text with audio.

Now, preview the composition to see how the audio keyframes adjust the scale of your text layer. Select the Audio button in the Time Controls palette to include music in your preview, and then click the RAM Preview button.

6. Edit the expression.

Audio amplitude values tend to be low. As a result, the text is likely to be too small. To increase the size, or scale, add a multiplier to the expression. Because expressions are too long to view in their entirety within the Timeline window, make edits by clicking anywhere in the expression and navigating with the right and left arrows. Type *10 after each of the two (“Slider”) values to magnify the amplitude by a factor of ten, thereby increasing the scale by a factor of ten. Click anywhere outside the expression to exit the edit mode. Try different multipliers to get the look you want.

Your final expression should look like this:

[thisComp.layer("Audio Amplitude").effect("Left Channel")("Slider")*10, thisComp.layer("Audio Amplitude").effect("Right Channel")("Slider")*10]

7. Animate the Hue property of the text layer.

Next, make the text appear more lively by animating its Hue property with the audio keyframes. In the Timeline window, expand the text layer and choose Fill Color > Hue from the Animate pop-up menu in the Switches column. Then, choose Animation > Add Expression. Drag the pick whip to the Both Channels slider to animate the Hue property using values from the audio keyframes. Then, type *10 (or a different value) at the end of the expression.

8. Preview the animation.

As you preview, note how the size and color of the text change as the volume of the audio changes. To add more interest, experiment with different types of music, create additional text layers, or add a background layer to your composition.

This is just one example of what you can do with audio amplitude keyframes—and only a fraction of what you can do with expressions! For more ideas on using these fun features, see the After Effects online Help.

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