Prerendering Layers and Sequences

Some layers are expensive to draw on every frame: a particle system, a grid of hundreds of cards, a stack of effects with motion blur, a long HTML page, a sequence full of layers. Prerendering renders such a layer once, in the background, to a transparent video, and plays that video in its place. Playback gets smoother, and a render of the whole project has less to do.

The Video Editor has two kinds of prerender:

	Layer Prerender	Prerender sequence
Where	The Prerender tab of the inspector	The SEQUENCE section of a selected sequence layer
Works on	Any layer that draws a picture, sequences included	Sequence layers
What it renders	The layer with everything applied to it: effects, transform, keyframes, speed curve, In and Out animations, filters, mask and sound	The sequence’s inner timeline
Used by	The preview and every export	The preview only; exports always render the sequence live
When you edit	The prerender goes stale and the layer plays live until you prerender again	Any edit inside the sequence drops the prerender
The file	Saved to the board’s Media Library	Kept out of the Media Library

Both need a saved project on a board, and both save the project for you before they start: the render is made from the saved timeline.

Layer Prerender

Prerender a layer

Select the layer.
Click Prerender on the inspector’s rail (the clapper icon, between 3D and Sound).
In the PRERENDER section, click Prerender.

The layer is rendered on its own, over transparency, for exactly the length it has on the timeline. While it runs, the section shows the stage and percentage over a progress bar; Cancel stops the render and leaves the layer as it is. A sound plays when it is done.

Layer Prerender works on video, image, text, shape, MotionFast, sequence, grid, particle, 3D model and HTML clip layers. Audio layers, adjustment layers, the camera and the Scene Rig can’t be prerendered and have no PRERENDER section. Grid and particle layers keep their own inspector layout without the rail; there, PRERENDER is one of the layer’s sections.

What changes once it is done

The rendered file is stored on the layer, and the preview and every export play it in the layer’s place for as long as it matches the layer.

The clip on the timeline gets a PRERENDER badge.
The PRERENDER section and its rail icon get the green dot that marks a changed section.
The section reads Prerendered with the file’s name; point at it to see when it was made.
The layer itself is untouched. The inspector, the timeline and undo still show the original layer with all its settings, so you can keep editing it.

The file is also saved to the board’s Media Library. Copies of the layer keep the prerender, and undoing an edit made after a long render doesn’t throw the render away.

When a prerender goes stale

Edit the layer in a way that changes its picture or its sound — move it, add an effect, trim it, change its speed curve or its volume — and the prerender no longer matches:

the badge turns amber and reads STALE,
the section reads Edited since the prerender — playing live,
the preview and exports play the layer live again, with your edits.

The file is kept until you prerender again, so undoing the edit brings the prerender back into use. A different project frame size or render frame rate makes a prerender stale too.

Some changes never make it stale: renaming the layer, moving it along the timeline, muting it, and changing its parent or track matte links. Those stay live on top of the prerender. The prerender always carries the layer’s sound, and muting the layer silences it as usual.

The buttons

Button	What it does
Prerender / Prerender again	Renders the layer from its current state and replaces the file. Use it after a prerender has gone stale.
Revert to Original	Removes the prerender from the layer. The layer plays live again, with all its edits. Undo brings the prerender back. Clicking the section’s green dot does the same.
Save as Rendered	Commits the render: the file becomes a new video clip in the project, named after the layer with (rendered), and the layer is rebuilt from default settings around it. From then on it is a plain video layer with the look baked in. It keeps its place on the timeline, its custom name, its mute, its cross transition with the clip before it and its parent and track matte links. One undo brings the original layer back. Disabled while the prerender is stale, because the file predates your edits.

What a layer prerender doesn’t include

The layer is rendered on its own, so anything that comes from outside it is not in the file: the layer it is parented to, its track matte source, the camera, and adjustment layers above it. Those keep working live on the prerendered layer.

When to use it

A heavy layer (particles, a large grid, many effects, motion blur) makes playback stutter.
A render fails because the graphics card is overloaded. The error names the heaviest layers on screen at that moment; prerender the heaviest one and render again.
You want a layer’s final look as a real video clip: prerender it, check it, then Save as Rendered.

Prerender a sequence

A sequence can hold dozens of layers, and the preview draws all of them on every frame. Prerender sequence renders the sequence’s inner timeline to a transparent video in the background, so the preview decodes one video per frame instead.

Select the sequence layer on the timeline.
In the Layer tab of the inspector, find the SEQUENCE section.
Click Prerender sequence.

The button shows Prerendering… with the percentage while it works — click it to cancel. When the render lands it reads Prerendered, and the preview plays the video instead of the live inner timeline. Click Prerendered to discard the prerender. If the render fails, the button reads Prerender failed — retry.

A sequence prerender is a preview aid:

Any edit inside the sequence drops it at once, as does a change of the project’s frame size or render frame rate. The preview goes back to the live inner timeline.
Exports always render the sequence live, at full quality, whether or not it is prerendered.
The file is kept out of the board’s Media Library and your Downloads.
Nested sequences can be prerendered too.

To use a sequence’s rendered look in exports as well, use Layer Prerender on the sequence layer instead.

Where to go next

Sequences and Presets — group layers into sequences and reuse them as presets
HTML Clips — web pages as layers, which can be prerendered like any other layer
Particle Solver — one of the heaviest layer types to prerender
Rendering and Output Formats — export the project
Performance Tuning — more ways to keep playback smooth