Collapse Transformations

Collapse Transformations

Switches Affect Nested Comps is enabled by default in General
Preferences. Enable frame blending or motion blur in a
master composition and those switches are passed through
to any nested composition. 3D position data and blending
modes, on the other hand, are ignored if Collapse Transformations
is not enabled. Enable it and it is as if
the precomposed layers resided in the Master comp.

Collapse Transformations prevents the application of a
blending mode on the collapsed layer. Apply any effect to
the layer (even disable it) and After Effects must render
the collapsed layer (making it what the Adobe developers
call a parenthesized comp, one that has qualities of being
both rendered and live). You can then apply a Blending
mode, but 3D data is not passed through.
Thus if you want to collapse transformations but not 3D data,
applying any effect—even one of the Expression Controls
effects that don’t by themselves do anything—will parenthesize
the comp. It’s a good trick to keep in your pocket.

Nested Time

After Effects is less rigid than most digital video applications
when working with time. All compositions in a given
project need not use the same frame rate, and as has been
shown, you can change the frame rate of an existing composition
on the fl y, and keyframes retain placement relative
to overall time.With power comes responsibility, of course, so pay particular
attention when you
. Import an image sequence.
. Create a new composition from scratch.
. Embed a composition with a given frame rate into
another with a different frame rate.
In the fi rst two cases you’re just watching out for careless
errors, but in the third, you might have reason to maintain
different frame rates in subcomps, in which case you must
set it deliberately on the Advanced tab of the Composition
Settings dialog, or apply the Posterize Time effect set to
the desired rate.