Adobe 25510629 - After Effects CS3 Professional, Руководство пользователя

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72 How to
If the overlay covers part of the subject that should be in front and repositioning is not an
option, then you may need to split the scene in two, and delete or adapt the overlay in the
second part. For example, assume that there’s a doorway behind the subject and the area from
the door frame to the left is part of the overlay to create the illusion that the subject is entering
the scene through that door. It's likely that the subject’s right hand would be behind the
overlay when gesturing. For instructions on getting around this type of situation, see
“Advanced compositing tasks” on page 72 .
Advanced compositing tasks
You may want or need to have an element in the foreground in one segment of a scene but in
the background in another segment. Moving all or part of an image from the foreground to
the background, or vice versa, can help you to get the subject on the correct side of a wall,
doorway, or pillar. This can also help create the illusion of dimension within the scene.
All of the overlays in a particular session are always in front of the subject. However, you can
achieve this illusion of dimension by breaking the scene into two or more sessions. You can
then use the same input clip in each session, trimming it appropriately by setting the In point
and Out point so that the segments blend seamlessly. You should break the sessions at a
timepoint where the subject is not in front of or behind the element that is swapping layers.
For more information, see
“Trimming the In and Out Points in a video clip” on page 104 .
The images below represent a three-part scene.
Trim times Overlay Composited shot
In Point: 0:00.00
Out Point: 0:10.00