Rotoscoping is referred to as a technique in which animators trace over footage, frame by frame, for use in live-action and animated films. Originally, recorded live-action film images were projected onto a frosted glass panel and re-drawn by an animator.
The music video for Aha’s “Take on Me” uses this technique.
However, “rotoscoping” can also refer to a special effects technique used in Adobe After Effects where a video clip is separated onto different layers using the rotobrush tool in order to manipulate depth. The rotobrush tool is simply a tool for selection within a video. To create this effect with images, separate your layers in photoshop, instead of rotobrushing in After Effects.
In the above example, the words “door zone” is cut off by the door creating an illusion of depth. This shot was composed by duplicating the video layer and then rotobrushing the clip to selecting for just the door. Then the door was arranged above text in the layers panel.
To begin rotobrushing in After Effects, import the video clip you want manipulate.
File > Import > File..
Next create a new composition.
Here are the setting we are using for HD video. Hit okay. This should open your new composition.
Next drag your footage from the project panel into the your new composition. If you want to maintain your footage in the background like we did in the example, duplicate your video layer by clicking and copy-and-pasting it. Lock your background layer and name the new layer “Rotobrush.”
Double click your “Rotobrush” clip within the layers panel inside your composition. This should open your open your clip in the layer window.
Next click the rotobrush tool button and move the playhead under the footage to the frame you want to start rotobrushing.
Working on top of your still frame, drag the mouse over areas you want to include in your selection and hold down option for areas you want to deselect.
Once you’re happy with your selection for the frame then extend the grey bar to tell After Effects how much of the clip to rotobrush. The program will generate a selection for you from frame to frame.
Move your playhead within the grey bar to finesse your selection using the same technique you used for the first frame.
Once you’re happy with your rotoscoping, click “freeze” and now you have isolated your video footage.
Return to the composition tab and make any adjustments needed to feather or smooth your rotoscoping.
Adjustments made without clicking the stopwatch will affect the clip consistently over time. To change these variables over time click the stopwatch and then click the diamond to create a keyframes on the timeline. However, in most cases this is not necessary.
Feel free to manipulate your layers to create interesting foreground/background interactions or change your background all together.