«PROFESSIONAL USER GUIDE © 2007 Adobe Systems Incorporated. All rights reserved. Copyright Adobe® After Effects® CS3 User Guide for Windows® and ...»
Jonas Hummelstrand and Dan Ebberts provide an animation preset and instructions for scaling and rotating a motion path: www.adobe.com/go/learn_ae_jonasscalemotionpath.
See also “Work with layer properties in the Timeline panel” on page 152 “About animation, keyframes, and expressions” on page 183 “Modify a Bezier mask path or shape path” on page 323 Show motion path controls
• To show motion path controls in the Composition panel, choose Composition View Options, and select Effect Controls, Keyframes, Motion Paths, and Motion Handles. To see a Position motion path in the Composition panel, the Position property must be selected.
• To show motion path controls in the Layer panel, choose the property or effect from the View menu at the bottom of the Layer panel.
• To specify how many keyframes to show for a motion path, choose Edit Preferences Display (Windows) or After Effects Preferences Display (Mac OS), and select an option in the Motion Path section.
Note: The current-time indicator does not need to be located on a keyframe before you drag it.
Drag a keyframe in the Composition panel to move one Position keyframe.
You can move multiple keyframes at one time by selecting them in the Timeline panel before you drag them in the Composition panel or Layer panel. To move the entire motion path, select all keyframes by clicking the property name in the Timeline panel before dragging a keyframe in the Composition panel.
Dragging all keyframes on a motion path by one keyframe
A new keyframe appears at the frame you clicked, on the motion path and in the Timeline panel. To move the keyframe, use the Selection tool.
Note: Though the results are different, the tools for manipulating motion-path curves with the Pen tool work in much the same way as those used to create and modify other Bezier paths, such as mask and shape paths.
Sketch a motion path with Motion Sketch You can draw a path for the motion of a selected layer using Motion Sketch, which records the position of the layer and the speed at which you draw. As you draw, a Position keyframe is generated at each frame.
Motion Sketch does not affect keyframes that you have set for other properties. For example, if you set Rotation keyframes for an image of a ball, you can use Motion Sketch to generate Position keyframes, so that the ball appears to roll along the path you created.
1 In the Composition or Timeline panel, select the layer for which you want to sketch a motion path.
2 In the Timeline panel, set the work-area markers to the duration in which you want to sketch motion.
3 Choose Window Motion Sketch.
4 Select the appropriate Motion Sketch options:
Show Wireframe Displays a wireframe view of the layer as you sketch the motion path.
Show Background Displays the static contents of the frame at which you started sketching in the Composition panel while you sketch. This is useful if you want to sketch motion relative to other images in your composition.
Smoothing Eliminates unnecessary keyframes from the motion path. This setting has the same result as using the Tolerance setting with The Smoother. Higher values produce smoother curves, but too high a value may not preserve the shape of the curve that you draw.
Note: You can smooth a motion path after it has been created by using the smooth expression or The Smoother.
Capture Speed At The ratio of the speed of the recorded motion to playback speed. If Capture Speed At is 100%, the motion is played back at the speed at which it was recorded. If Capture Speed At is greater than 100%, the motion plays back slower than it was recorded.
5 Click Start Capture and then drag in the Composition panel to create the motion path. Release the mouse button to stop capturing.
Note: After Effects automatically ends capturing when the capture time reaches the end of the work area (which, by default, is the composition duration).
See also “Set the work area” on page 112 “About animation, keyframes, and expressions” on page 183
• A path copied from Illustrator or Photoshop You can paste any of these paths into the Position or Anchor Point property for a layer, or into an effect control point’s position property. The pasted keyframes are set to rove in time, except for the first and last ones, to create a constant velocity along the path.
By default, the duration of the pasted motion path is 2 seconds. You can adjust the duration by dragging the first or last keyframe in the Timeline panel.
1 Copy a path to the clipboard:
• Select a Path property in the Timeline panel, and choose Edit Copy.
• Select a path in Illustrator or Photoshop, and choose Edit Copy.
2 In the Timeline panel, select the property into which to paste the path. The property must be animated—that is, it must have at least one keyframe or an expression.
3 Place the current-time indicator at the time for the first keyframe of the motion path.
4 Choose Edit Paste.
See also “Copy a path from Illustrator, Photoshop, or Fireworks” on page 324 “About paths” on page 313 Assorted animation tools Use motion blur When you view one frame of motion-picture film or video containing a moving object, the image is often blurred, because a frame represents a sample of time (in film, a frame is 1/24 of a second long). In that time, a moving object occupies more than one position as it travels across the frame, so it doesn’t appear as a sharp, still object. The faster the object moves, the more it is blurred. The camera shutter angle and shutter phase also affect the appearance of the blur, determining how long the shutter stays open and when the shutter opens relative to the beginning of the frame.
In contrast, in a single frame of a computer-generated animation, you may not be able to tell which objects are moving because all moving objects may appear as sharp and clear as nonmoving objects. Without motion blur, layer animation produces a strobe-like effect of distinct steps instead of an appearance of continuous change. Adding motion blur to layers you animate in After Effects makes motion appear smoother and more natural.
You enable motion blur for each layer individually, and you also determine whether the motion blur is rendered for previews and final rendering. Use the Enable Motion Blur composition switch at the top of the Timeline panel to enable or disable motion blur rendering for previews. Modify the render settings in the Render Queue panel to enable or disable motion blur rendering for final output.
Motion blur slows rendering, so you may want to disable the composition switch while working, and only enable it when you need to see the finished result.
AFTER EFFECTS CS3 201 User Guide You can use motion blur when you animate a layer—for example, moving a layer of text across the screen. You cannot add motion blur to motion that already exists within a layer, such as live-action video, by means of the Motion Blur layer switch and Enable Motion Blur composition switch. You can add motion blur to motion within a layer by using an effect. The CC Force Motion blur effect, which is included in the full version of After Effects, analyzes motion from frame to frame within a layer and uses this information to add motion blur to motion within the layer. The
ReelSmart Motion Blur effect from RE:Vision Effects performs a similar function:
If you want to smooth live-action video to which you assigned a frame rate much lower or higher than the original, use frame blending.
Note: Previous versions of After Effects included an effect called Motion Blur. That effect is now named Directional Blur, to avoid confusion with motion blur applied to layers.
• Click the Motion Blur layer switch for the layer in the Timeline panel.
• Select the layer and choose Layer Switches Motion Blur.
The number of samples that After Effects uses to calculate motion blur adapts for each layer, depending on the motion of that layer. This provides high-quality motion blur without unnecessarily sampling the motion of a slowmoving layer as frequently as that of a fast-moving layer. High sampling rates decrease rendering performance.
See also “Apply frame blending to a layer” on page 225 “Apply motion blur to a mask” on page 267 “Work with render settings” on page 597 “About effects” on page 348 Motion blur settings in the Advanced tab of Composition Settings Samples Per Frame The minimum number of samples. This is the number of samples used for frames for which After Effects is not able to determine an adaptive sampling rate based on layer motion. This sample rate is used for 3D layers and shape layers.
Adaptive Sample Limit The maximum number of samples.
Smooth motion and velocity Smooth motion paths, value curves, and velocity curves to eliminate bumpiness or excess keyframes using The Smoother, which adds keyframes or removes unnecessary keyframes. You can also use the smooth expression to accomplish this.
Although you can smooth a curve for any property, The Smoother is most useful when applied to curves that have been automatically generated by Motion Sketch, where you may have excess keyframes. Applying The Smoother to keyframes that have been set manually may result in unexpected changes to the curve.
Note: To avoid the need to use The Smoother on a path generated by Motion Sketch, set the Smoothing option in the Motion Sketch panel before sketching the motion path.
When you apply The Smoother to properties that change spatially (such as Position), you can smooth only the spatial curve (the curve defined by the motion). When you apply The Smoother to properties that change only in time (such as Opacity), you can smooth only the value and velocity curves (the curve defined by the value or the velocity).
In addition to adding keyframes or eliminating unnecessary keyframes, The Smoother also applies Bezier interpolation at each keyframe when smoothing the temporal curve.
1 In the Timeline panel, either select all the keyframes for a property to smooth the entire curve, or select at least three keyframes to smooth only a portion of a curve.
2 Choose Window The Smoother. In the Apply To menu, The Smoother automatically selects Spatial Path or Temporal Graph, depending on the type of property for which you selected keyframes in step 1.
3 Set a value for Tolerance. The units of Tolerance match those of the property you are smoothing. New keyframe values will vary no more than the specified value from the original curve. Higher values produce smoother curves, but too high a value may not preserve the original shape of the curve.
4 Click Apply and preview the results.
5 If necessary, choose Edit Undo The Smoother to reset the keyframes, adjust the value for Tolerance, and then reapply The Smoother.
See also “Sketch a motion path with Motion Sketch” on page 199 “Select keyframes” on page 188
3 For Apply To, select the type of curve you want The Wiggler to change. If you selected keyframes for a property that varies spatially, you can select Spatial Path to add deviations to the motion, or Temporal Graph to add deviations to the velocity. If you selected keyframes for a property that does not vary spatially, you can select only Temporal Graph.
4 Select a Noise Type option to specify the type of deviation due to randomly distributed pixel values (noise):
Smooth Noise Produces deviations that occur more gradually, without sudden changes.
Jagged Noise Produces sudden changes.
5 Select the dimensions of the property you want to affect:
One Dimension Adds deviations to only one dimension of the selected property. Choose the dimension from the menu.
All Dimensions Independently adds a different set of deviations to each dimension.
All Dimensions The Same Adds the same set of deviations to all dimensions.
6 Set Frequency to specify how many deviations (keyframes) per second After Effects adds to the selected keyframes. A low value produces only occasional deviations, while a high value produces more erratic results. A value between 0 and 1 creates keyframes at intervals of less than one per second. For example, a value of 0.5 creates one keyframe every 2 seconds.
7 Set Magnitude to specify the maximum size of the deviations. After Effects sets the specified magnitude to the units of the selected property, so a value for one property may produce very different results in another property.
8 Click Apply and preview the results.
9 If necessary, choose Edit Undo The Wiggler to reset the keyframes, adjust the values for Frequency and Magnitude, and then reapply The Wiggler.
See also“Select keyframes” on page 188
Convert audio to keyframes The Convert Audio To Keyframes keyframe assistant analyzes audio amplitude within the work area and creates keyframes for audio amplitude.
❖ Select the Timeline panel, and then choose Animation Keyframe Assistant Convert Audio To Keyframes.
This keyframe assistant creates a new Audio Amplitude layer representing all audio sources in the composition, with three Expression Controls effects with Slider properties that contain the keyframes: Left Channel, Right Channel, and Both Channels.
To make use of the keyframes created by this keyframe assistant, you must link the changes in audio amplitude to other layer properties. For example, use an expression to link the audio keyframes to the Scale property of a layer to make the layer grow and shrink as the amplitude increases and decreases.
Aharon Rabinowitz provides a video tutorial that shows how to link the audio amplitude keyframes to other
properties, in this case the properties of the Wave Warp effect, to synchronize animation with sound:
The Trapcode Sound Keys effect also converts audio values to keyframes, but provides more control than the builtin Convert Audio To Keyframes keyframe assistant: www.adobe.com/go/learn_ae_trapcodesoundkeys.
AFTER EFFECTS CS3 204 User Guide
See also“Set the work area” on page 112