Comp Source

Renders another composition inside this one — the nested composition becomes a texture, clipped to its own frame and placed centered at its own size.

Category: Source Menu path: Source > Comp Source

Ports

Port	Type	Direction	Description
out	imageRgba16f	output	The nested composition's rendered frame
audio	audio	output	The nested composition's mixed audio. Wire it into the Output node's Audio input to hear and export it; leave it unwired to nest the picture alone.

Parameters

Param	Type	Default	Description
sourceCompId	string	""	The composition to render. Picked from a dropdown in the Properties panel that lists every composition this one can nest without creating a loop. An Open button next to it jumps into the nested composition for editing.
timeMode	enum	Layer	Layer: the nested composition starts at this layer's in-point and follows the clip (trimming the layer's start or sliding it shifts what plays). Composition: the nested composition's frame N plays at this composition's frame N regardless of the layer's in-point.

How It Works

Comp Source is how compositions nest (a "precomp"). The engine renders the referenced composition first — at its own resolution, frame rate, and duration, with its own layers, mattes, and motion blur — then places that finished frame into this composition's canvas, centered, one nested pixel per composition pixel. Anything in the nested composition that extends past its own frame is clipped, exactly as it would be if you exported that composition on its own. Transform, effects, and compositing then apply to the placed texture like any other image: put a Transform 2D after Comp Source to move or scale the whole nested composition.

Time is mapped per layer. With the default Layer time mode the nested composition plays from its first frame at this layer's in-point (the layer's offset shifts it), so trimming and sliding the clip behaves like a video clip. Frame rates are reconciled automatically: nesting a 60 fps composition in a 30 fps one advances two nested frames per host frame. Past the nested composition's duration the layer shows nothing.

Editing a nested composition updates every place it is used — the viewer, RAM previews, and exports all pick up the change immediately, and static nested compositions cache like any other unchanged image. A composition cannot nest itself, directly or through a chain; the picker hides those options, and a reference that becomes circular renders blank.

Audio

Comp Source has an Audio output alongside its image, the same way Audio Source does. Wire it into the Output node's Audio input and every Audio Source inside the nested comp (and inside anything it nests in turn) plays and exports through this layer, on the layer's clock: the same in-point, offset, time mode, and frame-rate handling that place the picture also place the audio, and nothing is heard outside the layer's clip or past the nested comp's duration. The layer's Output node acts as a bus: its Audio Gain, Audio Pan, and Mute apply to the whole nested mix, on top of whatever levels the nested comp's own layers set. This holds for live playback, RAM preview, and every export that carries audio.

Leave the Audio port unwired and the nested comp is silent here, even if it has sound of its own. Dropping a comp onto the timeline or viewer wires the port automatically when the comp has audio, so the default matches what you'd expect; disconnect it when you only want the picture. To combine this audio with other sounds on the same layer, run it through an Audio Mix, which gives it its own dB level there.

The timeline does not yet draw a waveform on a nested layer.

Usage Examples

Basic: Reuse an animated element

1. Build the element (a logo, a lower third) in its own composition
2. In the main composition, drag that composition from the Assets panel onto the timeline or viewer — a layer wired Comp Source → Output appears, named after the composition and trimmed to its length (with the Audio port wired too if the comp has sound)
3. Click the layer in the viewer to get a Transform 2D and position it

To nest a composition into a layer you already have, drag it onto the node graph instead: a Comp Source node pointed at it lands at the drop point, ready to wire.

Creative: Treat a whole composition as footage

Nest a composition, then run it through effects that need a single image: a Blur, a Tile, a UV Remap driven by a Noise field, or a Matte cut by a shape on another layer. Everything inside the nested composition stays editable — double-click it in the Assets panel or use the Open button in Properties.

Time offsets

Nest the same composition on several layers with different in-points to stagger copies of one animation. Each layer maps time independently.

Tips

• The nested composition renders at its own size. To fill a larger host, scale it with Transform 2D, or make the nested composition bigger.
• Content past the nested composition's frame is clipped by design. Enlarge the nested composition if you need overshoot to survive (a shadow or glow near its edge, for instance).
• Motion blur on the host layer blurs the placed texture's transform; the nested composition's own layers blur on their own settings. The shutter does not sample inside the nested composition at sub-frame times.
• Nesting is capped at eight levels deep; deeper references render blank with a console warning.
• Layer Source is the within-composition cousin: it references another layer of the same composition. Comp Source references a different composition.

Related Nodes

• LayerSource — reference another layer's output inside the same composition
• ImageSource — the same placement rules, for a still image
• VideoSource — clip-time mapping works the same way as timeMode: Layer
• Merge — combine the nested composition with other textures on one layer
• AudioMix — combine its audio with other sounds on one layer