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AE6.0 Overview Part 3: Motion Tracking

Single Point Tracking By Stephen Schleicher
Even better than being able to stabilize a shot is the ability for After Effects 6.0 to track regions or points in a layer and apply that tracking information to another layer in your composition. With the tracking feature, it becomes a simple matter of making computer-generated graphics, effects, or even complex compositions follow a point in your video.

The simplest type of motion tracking is to track a single point in a layer. As you may have guessed, this is very similar to tracking data for image stabilization that we covered in the last installment.


If you havent read parts one and two, you should become familiar with the interface by clicking here and here.

Even if you didnt read the last two installments, it is important to remember that the Anchor Point does not need to be located inside the Feature region box. The Anchor Point could be located outside the Feature region box because the area you want to place tracked layer could be a difficult area to get a solid lock.

In this exercise, well take some buttons created in Adobe Photoshop and track them to the tips of the subjects fingers creating a futuristic/Minority Report-ish type interface.

For this exercise, you can
download the project files and project here. These are in .sit format and are quite large.

Step 1: Create a new project (Option+command+N or Control+Alt+N) and import (Command+I or Alt+I) the video file and the button elements.

The button elements are layered Photoshop files. Bring them in as separate layers.

If you are not sure if the layered graphic you are importing has transparencies or not, begin with merged layers and check. If it has a non-transparent background layer, you will need to reimport the footage and choose the appropriate layer.


Step 2: Create a new composition by clicking and dragging the trackpoint.mov clip to the Create New Composition icon in the Project window.

If you look at the actors (i.e. ME) fingers closely, you will see red dots on the ends of the fingers. It is these dots that you will track the Photoshop buttons to. As a lucky twist of fate the actors fingers move so quickly at the beginning of the movement that the red dots are obscured until they reach the point where a button will be positioned. This saves us from having to digitally paint out the dots later on (although with the new Clone Tool this would be an easy fix).

Tracking dots on your subject (or on a blue screen wall) will serve as an easy way to track CG elements later on.


Step 3: Scroll through the Timeline until the actors left hand is at a position where he appears to be clicking on a button (Command+G or Alt+G and enter 1:06 to Go To Time).

Step 4: Position one of the interface buttons (in this case Purple Triangle Right) directly over the red dot on the actors finger. Make sure that the In point for the button layer is at the beginning of the Timeline, otherwise, the button will pop on screen.

Tracking markers can serve as a guide to properly place an element.


For this exercise well deal with just one button. Once you understand the tracking process, you can do the second track yourself.


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Related Keywords:Adobe, After Effects 6.0, ae6, tracking, motion tracking, single point tracking, schleicher

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