Adobe After Effects CS4 - Manual (Page 268)

262 USING AFTER EFFECTS CS4
Animation and keyframes
Last updated 12/21/2009
David Torno provides extensive video tutorials that show how to use mocha-AE as part of a workflow to replace one
face with another in a movie. Todd Kopriva provides links and details on his
After Effects Region of Interest blog.
Mathias Möhl provides the MochaImport script and a set of related tutorials on his AExtensions website .
MochaImport automates common parts of the workflow of using mocha-AE with After Effects.
Jeff Foster provides tips and tutorials about mocha for After Effects on his Pixel Painter website .
Jeff Foster provides a tutorial on the ProVideo Coalition website that demonstrates the use of mocha for After Effects
to replace a sign on the side of a moving truck in a shaky video clip.
Motion tracking overview and resources
With motion tracking, you can track the movement of an object and then apply the tracking data for that movement
to another object—such as another layer or an effect control point—to create compositions in which images and effects
follow the motion. You can also stabilize motion, in which case the tracking data is used to animate the tracked layer
to compensate for movement of an object in that layer. You can link properties to tracking data using expressions,
which opens up a wide variety of uses.
After Effects tracks motion by matching image data from a selected area in a frame to image data in each succeeding
frame. You can apply the same tracking data to different layers or effects. You can also track multiple objects in the
same layer.
For information about Imagineer Systems mocha for After Effects, see “ Tracking and stabilizing motion ” on page 261.
More Help topics
“ Expression basics ” on page 646
Uses for motion tracking and stabilization
Motion tracking has many uses. Here are some examples:
• Combining elements filmed separately, such as adding video to the side of a moving city bus or a star to the end of
a sweeping wand.
• Animating a still image to match the motion of action footage, such as making a cartoon bumblebee sit on a swaying
flower.
• Animating effects to follow a moving element, such as making a moving ball glow.
• Linking the position of a tracked object to other properties, such as making stereo audio pan from left to right as a
car races across the screen.
• Stabilizing footage to hold a moving object stationary in the frame to examine how a moving object changes over
time, which can be useful in scientific imaging work.
• Stabilizing footage to remove the jostling (camera shake) of a handheld camera.
Depending on the encoder you use, it is possible to decrease the size of your final output file by stabilizing motion
footage. Random motion, such as from the jostling of a handheld camera, can make it difficult for many
compression algorithms to compress your video.
Motion tracking user interface and terminology overview
You set up, initiate, and apply motion tracking with the Tracker panel.
As with all properties, you can modify, animate, manage, and link tracking properties in the Timeline panel.