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From the author of Compositing in the Timeline

Compositing in the Timeline

One of After Effects’ greatest strengths is its ability to composite elements. After Effects offers several powerful options including track mattes, layer masks, and 3D space. These options provide you with precise control on how the layers are mixed together in the Composition panel.

Using Track Mattes

Track mattes allow you to use one layer to create holes that allow another layer to show through. For example, you can use the shape of one layer (the matte) to define a pattern that the underlying layer (the fill) shows through.

Let’s use a second instance of the Blue BG pre-comp to create a masked effect.

  1. Select the Blue BG pre-composition in the Timeline panel.
  2. Choose Edit > Duplicate to create a second instance of the pre-comp.
  3. Drag the new copy so it is the second layer in the Timeline stack.
  4. Choose Edit > Deselect All so no layers are active.
  5. Click the Magnification ratio pop-up menu and choose 25% to see more of the canvas space.
  6. Click in the toolbar and choose Ellipse Tool.
  7. Drag with the Ellipse tool to create a shape.
  8. Activate the Selection tool in the toolbar.
  9. Click and drag the control handles to resize the shape layer as needed. You can click near a corner handle to rotate the shape layer.
  10. Drag the shape layer so it is immediately above the top instance of Blue BG.
  11. Click the Toggle Switches/Modes button to see blending modes.
  12. For the Blue BG layer, click the TrkMat menu to access the track matte controls:
    • No Track Matte. No transparency is created; next layer above acts as a normal layer.
    • Alpha Matte. Opaque when alpha channel pixel value is 100%.
    • Alpha Inverted Matte. Opaque when alpha channel pixel value is 0%.
    • Luma Matte. Opaque when the luminance value of a pixel is 100%.
    • Luma Inverted Matte. Opaque when the luminance value of a pixel is 0%.
  13. Choose Alpha Inverted Matte. The top copy of Blue BG only shows through where the ellipse shape does not exist. The mask layer automatically has its visibility turned off.
  14. Click the Magnification ratio pop-up menu and choose Fit. Then choose File > Save to save your work.

Using Masks

Another way to apply selective transparency in After Effects is to use masks. A mask is essentially a vector-based path that can be applied to a layer. You can create masks using the Shape or Pen tools. Additionally, you can copy and paste paths from Illustrator to a selected layer in After Effects for even more options. Let’s experiment with shapes by adding a vignette.

  1. Click the topmost layer in the Timeline and press the Home key.
  2. Choose Layer > New > Solid. The Solid Settings window opens.
  3. Enter Vignette into the Name field. Click the color swatch at the bottom of the window. A new window opens. Set the color to black and click OK. Click OK again to create the solid layer.
  4. Double-click the Ellipse tool to add an elliptical mask to the Vignette layer. The layer is masked, but it needs modification.
  5. The basic Mask properties are visible. Press M to hide them.
  6. Press MM to access the advanced Mask properties.
  7. Select the Inverted check box to invert the mask.
  8. Set Mask Feather to 250. Set Mask Opacity to 80%.
  9. Click the RAM Preview button to see the results so far. Choose File > Save to save your work.

Using 3D Space

After Effects offers powerful support and several options for 3D space. These options allow for objects to be rotated or positioned along the X, Y, or Z axes. To work in 3D space, an object must be converted to a 3D layer.

  1. Select logo start in the Timeline. Click its eye icon so it is active.
  2. Click the Toggle Switches/Modes button.
  3. Select the 3D column (it uses a cube-shaped icon).
  4. Press P for Position. Set the layer to 775.0, 325.0, 0.0.
  5. You want to animate the layer in 3D space so it swings into place. So you need to adjust the anchor point of the layer so it rotates around the left edge. Select the Pan Behind tool from the toolbar to adjust the layer’s anchor point without changing the visible position of the layer.
  6. Drag the anchor point of the layer so it lands just outside the logo.
  7. Figure 37 Using the Pan Behind tool, drag the anchor point to the outside edge to the right of the logo. Since the layer was trimmed, be sure to move the Current Time Indicator to view the logo.

  8. Press R for rotation to control the layer.
  9. Press I to move to the layer’s In point.
  10. Click the stopwatch to add a rotation keyframe for the Y Rotation. Enter a starting value of 60.0˚.
  11. Click the time display (at the bottom of the Composition panel or in the upper-left corner of the Timeline). Enter 2:25, and press Return (Enter).
  12. Set the Y Rotation to 0.0˚.
  13. Click the RAM Preview button to see the results so far. Choose File > Save to save your work.

Using Animation Presets

To speed up tasks, After Effects offers several animation presets that you can apply to layers. Included with After Effects are several options for Backgrounds, Shapes, Text, and Transitions. Additionally, more can be downloaded from Adobe’s Web site at http://www.adobe.com/cfusion/exchange.

Let’s apply one of the presets as a transition.

  1. Select the layer logo start in the Timeline.
  2. Press I to go to the layer’s In point.
  3. Click the Effects & Presets panel.
  4. Click the disclosure triangle next to * Animation Presets.
  5. Click the triangle next to Transitions – Dissolves. There are several options available.
  6. Knowing what each effect does by simply looking at its name is difficult. Fortunately, After Effects makes browsing easy. Click the submenu in the Effects & Presets panel and choose Browse Presets.
  7. Bridge opens with a folder for each category. Double-click the Transitions – Dissolves category to view the previews.
  8. Click a thumbnail to preview the Animation Preset.
  9. Let’s use the Dissolve – vapor.ffx on the logo layer. Double-click to apply the effect to the selected layer. Bridge is hidden and After Effects becomes the active application.
  10. Click the RAM Preview button and review the effect. The two transitions applied have different durations. Let’s confirm this by examining the keyframes applied to the layer.
  11. With the logo start layer selected, press U to see all the user added keyframes. If the keyframes are hidden, press U again to reveal them. This is a useful shortcut to quickly access animation controls. You now see two sets of keyframes and two expressions that are controlling the animation. Expressions are small computer programs written in a language called Javascript—a language similar to Flash’s ActionScript.
  12. Closely examine the sets of keyframes. Notice how the first two frames line up, but the second set does not.
  13. Click the second keyframe, hold down the Shift key, and drag the second keyframe for the Transition Completion property. As you get near the next keyframe, it snaps into place.
  14. Click the RAM Preview button to see the results so far. Choose File > Save to save your work.
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