Chapter 28: AE Comps and Comp Layers

An AE comp is an After Effects composition brought into your template the way it was built: its own layers, its own size, frame rate and duration. A Comp Layer places a comp in a scene — or inside another comp — with its own timing, the way a precomp layer does in After Effects. Comps are fully editable: open one and the canvas becomes that comp, with a breadcrumb back to where you came from.

AE comps are not imported scenes. An imported scene (Chapter 16) is a read-only snapshot of a scene from another FX Express template. An AE comp comes from an After Effects project and is yours to edit. Each has its own tab in the Media panel.

Where comps come from

How	What you get
New Template from an `.aep`, or File ▸ Import Template… with an `.aep`	A new template: the project’s main composition becomes the scene, and every composition it uses becomes an AE comp
Media ▸ Import ▾ ▸ After Effects comps…	The comps of a project added to the template that is open — the main composition and every composition it uses, all as comps. No scene changes; you place them

Both read the project the same way, and both take a zipped Collect Files folder in place of the .aep to bring its footage along; Chapter 27 describes what comes across. There is no way yet to make an empty comp, or to precompose a selection, in the editor.

Importing comps into an open template

Open the Media tab in the left sidebar.
Click Import ▾ and choose After Effects comps….
Pick the .aep file, or a ZIP of the folder After Effects’ Collect Files wrote.

The project is read on the server, which takes a few seconds; from a ZIP, each footage file the comps use is uploaded beside the template first, which takes as long as the files are large. When it is done, the Media panel switches to its AE Comps tab and the import report opens: what came across, the media and fonts the project only references, the comps it brought, and everything that could not be carried over.

A comp whose name is already used in this template gets 2, 3… added.
The variables the comps use are added to the template’s variables, with the value the project held. A variable the template already has keeps its value.
The import is one step: Undo removes every comp it added.

If the project cannot be read — an .aepx, a ZIP with no project or with two, or a file that is not an After Effects project — an Import failed dialog gives the reason, with the same AEP_… codes the New Template dialog shows, and the template is left exactly as it was. AEP_COMPS_UNAVAILABLE: This needs the updated After Effects importer — the server returned an older format. means the server answered in the older, flattened format: until it is updated, import the project with New Template, which still works (flattened).

The AE Comps tab

The Media panel has three tabs under its Import ▾ button — Files, Scenes and AE Comps. It remembers the last one you picked.

AE Comps shows every comp in the template as a card:

a thumbnail at the comp’s own aspect ratio
its name, and a line such as 1920×1080 · 25 fps · 4.0 s
how many Comp Layers use it

Hover a card for rename (pencil — rename in place) and delete (trash). Delete asks first and tells you how many layers use the comp; deleting it also removes every Comp Layer that shows it.

With no comps yet the tab reads None yet. Use Import → After Effects comps…

Placing a comp

Drag its card onto the canvas. It lands as a Comp Layer centred on the drop point, at the comp’s natural size — one comp pixel per canvas pixel — and shrunk to fit if the comp is bigger than the canvas.

A comp can be placed any number of times, in scenes and inside other comps. Every placement shows the same comp.

You cannot place a comp inside itself, or inside a comp that it already contains, directly or further down: the drop — or a paste of such a Comp Layer — is refused with a message.

Opening a comp

Any of these opens a comp for editing:

double-click a Comp Layer on the canvas
select a Comp Layer and choose Edit comp in its floating toolbar
double-click the comp’s card in the AE Comps tab

While a comp is open:

the canvas takes the comp’s own width and height
the timeline shows the comp’s layers and its duration, and Play plays the comp’s own timeline
everything you do to layers works as in a scene — add, move, restyle, animate, group, delete, copy, paste, duplicate
with nothing selected, Copy and Duplicate do nothing (in a scene they would take the whole scene; a comp is not a scene), and a copied scene cannot be pasted inside a comp
the Preview button’s “Current Scene” entries and View ▸ Preview Current Scene are unavailable — Play the comp’s timeline instead, or preview the entire video
edits change the comp itself, so every Comp Layer that shows it updates at once, in every scene
undo and redo work as everywhere; undoing inside a comp keeps it open as long as it still exists

Above the canvas a breadcrumb shows where you are. Opened from a layer in Scene 1, and then from a layer inside that comp, it reads Scene 1 › Lower third › Logo. Opened from the AE Comps tab, it starts at the tab: AE Comps › Lower third.

Click a crumb to go back up to it.
Press Esc to go up one level. If a layer is selected, the first Esc deselects it; Esc leaves text fields and dialogs alone, and stops play-in-place first. Once nothing is selected, Esc goes up one comp level.
Selecting a scene in the Scenes panel closes the comp and goes straight to that scene.

Comp settings

With a comp open and nothing selected, the properties panel shows the comp’s settings:

Setting
Comp Name	Editable
Duration	Editable, in seconds — how long the comp runs before a Comp Layer holds or loops it
Thumbnail	Poster Time: the frame shown on the comp’s card in the Media panel. Editable
Background	Editable. Transparent by default: a comp draws over whatever lies beneath its layer
Size	Read-only: the comp’s width × height in pixels
Frame rate	Read-only

The panels that only make sense for a scene of the movie are hidden while a comp is open: transition, scene mode and conditions, scene sounds and voiceover, subtitles, and endcard. A comp only ever plays inside a Comp Layer.

Frame rate. A comp keeps the frame rate After Effects gave it, for reference, but always plays at the template’s frame rate — After Effects’ own default for nested comps.

Comp Layer properties

From the outside a Comp Layer is an ordinary layer: position, size, scale, rotation, anchor, opacity, blend mode, effects, track matte, keyframes, appearance animation and the visibility switch all work as on any layer. Hiding a Comp Layer is how you switch a whole comp off.

Its floating toolbar has the layer name, Edit comp, timing, Animate… and lock. Its own section in the Layer properties has:

Control	What it does
Comp	Which comp the layer shows, with an Open link
Content Offset (s)	How far into the comp the layer starts: at the layer’s In Time the comp is already this many seconds in, like a video’s Content Offset. It cannot go below 0
Stretch (%)	The comp’s speed. 100% plays it as built; 200% plays it at half speed, taking twice as long; 50% at double speed. Must be above 0
Loop	When the layer runs longer than the comp: off (the default) holds the comp’s last frame, on starts the comp over
Reset to comp size	Puts the layer’s box back to the comp’s natural size
Variable mapping (blank = same name)	Which template variable each of the comp’s variables reads — see below

Resizing a Comp Layer’s box out of proportion stretches its content, in the editor and in the rendered movie alike.

Variable mapping

Inside a comp, the variables in text, media and visibility conditions have names of their own — the comp’s local names. Each Comp Layer decides which template variable each one reads, for that placement only. The Variable mapping (blank = same name) table has one row per variable the comp exposes: the names its own layers use, plus the names its nested Comp Layers map to. Pick an existing template variable for a row, or type a new name.

A row you leave alone passes straight through: the comp’s {title_01} reads the template’s title_01. Publishing writes the mapped names into the movie, so the rendered video follows the mapping exactly as the editor shows it.

That is how one comp serves several placements. A lower third placed twice can show two different titles: the first Comp Layer leaves title_01 as it is, the second maps title_01 → title_01_2. The After Effects importer fills these mappings in for you, reproducing the variable names a flattened import used to give, so a template’s personalisation fields do not change because its precomps are now comps.

Comp Layers on the timeline

A Comp Layer’s bar has its own icon and colour.
Drag its ends to set In Time and duration, as for any layer.
Shift-drag the content bar to change Content Offset, as with a video (Chapter 10): dragging left starts the layer later in the comp. It stops at 0.
The comp’s end is marked on the bar. Past it the layer holds the comp’s last frame, or starts over with Loop.
The row does not expand into the comp’s own layers; double-click the layer to open the comp instead.

Nesting

Comps can contain Comp Layers of other comps, to any depth. A comp can never end up inside itself: every way of placing one checks first. A hand-edited template file that loops anyway is cut off after 10 levels, in the editor and at publish, and publishing warns about it.

When a comp is missing

A Comp Layer whose comp no longer exists — only possible in a hand-edited file, since deleting a comp removes its layers — shows a dashed Missing comp box. Publishing skips it with a warning.

Limits

Stretch and video. A video inside a stretched comp plays at its normal speed in the rendered movie.
Audio inside comps. Audio layers inside a comp do not play in the editor’s play-in-place.
Motion tracking cannot be applied to a Comp Layer.
Not carried from After Effects: time remapping (a remapped comp plays straight through), Collapse Transformations (the comp is drawn as one flat picture) and “Preserve frame rate when nested”. The import report names each case.
Pre-encoding treats a Comp Layer as one unit, so a template that used to import flattened may prepare less in advance at publish.

AE comps and imported scenes

	AE comp	Imported scene
Comes from	An After Effects project	A scene of another FX Express template
Editable	Yes — open it	No — re-import to change it
Size	Its own width × height	The template canvas
Media resolves against	This template’s folder	The source template’s folder
Variables	Mapped per Comp Layer	Fixed
Media tab	AE Comps	Scenes
Placed by	Comp Layer	Scene layer

Scene from template… does not bring comps along. Importing a scene from another template (Chapter 16) takes the scene’s own layers only: its Comp Layers are left out, so their contents are missing in the imported scene. The Import Scene dialog warns you when the scene you pick has any. To reuse an After Effects template’s comps in another template, import them from the .aep with Media ▸ Import ▾ ▸ After Effects comps… instead.

Troubleshooting

I can’t drop a comp onto the canvas while another comp is open. The comp you are dropping already contains the one that is open, so the drop would put a comp inside itself. Place it in a scene, or in a different comp.

I changed a comp and every placement changed. That is what a comp is: one design shown by every Comp Layer that uses it. To make one placement differ, change the layer itself — its timing, Content Offset, Stretch, or its variable mapping.

Two placements of the same comp show the same text. Both Comp Layers read the same template variable. Select one and map the comp’s variable to a different template variable in its Variable mapping.

Esc doesn’t leave the comp. A layer is still selected (the first Esc deselects it), you are in a text field or a dialog, or play-in-place is running (Esc stops it). Press Esc again once none of those applies, or click a crumb in the breadcrumb.

After Effects comps… says it needs the updated importer. The server still runs the previous After Effects importer, which only knows the flattened format. Until it is updated, import the project with New Template.

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