Smart Animate

Put your "before" in one composition and your "after" in another, give the elements the same names in both, and run Smart Animate to "…". You get a third composition — Before → After — where matching layers move, resize and rotate into place, layers that only existed in the first fade out, and layers that only existed in the second arrive.

After Effects has no equivalent. Figma's Smart Animate and Keynote's Magic Move are the reference; this is the same idea for a timeline.

How layers pair up#

Naming is how designers already express identity, so that is what the matcher reads. In priority order:

Kind must always agree. A text layer never matches a video, however alike the names.

There is deliberately no geometric or visual similarity rule. "Both roughly square and roughly here" produces matches nobody asked for, and a wrong match is far worse than none: an unmatched layer just fades, which reads as a deliberate cut, while a wrong one flies across the screen and turns into something else.

Each pass consumes what it matched, so a strong signal always beats a weak one — a layer paired by name is never re-paired by text later.

What gets written#

Only what actually differs. A layer whose position is identical in both boards gets no position track at all. That is not an optimisation: writing every property for every layer would bury the three things that move under ninety that do not, and the whole promise here is that the result is ordinary keyframes you go and tune afterwards.

Differences below a per-property noise floor are ignored too — positions that differ in the twelfth decimal are the same position, and a track for that is a flat line cluttering the graph editor.

Tweened: x, y, anchorX, anchorY, width, height, scale, scaleX, scaleY, rotation, opacity.

Departures and arrivals do not cross-dissolve#

A leaving layer holds at full opacity while everything else starts moving, then fades over the first 40% of the transition. An arriving layer stays invisible until 60% through, then fades up.

Those two numbers are one constant, and it has a correctness bound: above 0.5 the two fades overlap, which puts the old and new element on screen together — a cross-dissolve, which is exactly the look Smart Animate exists to replace. At 0.4 the outgoing layer is gone before the incoming one starts, and the gap between them is covered by the matched layers still moving.

The hold matters as much as the fade. Fading a departure from the first frame makes the board look like it was already dissolving; letting it sit while the layout rearranges around it reads as an exit.

It never edits either board#

The transition is built in a duplicate of the first composition. Both boards are things you designed and will keep designing — animating one in place would mean the source of the transition no longer shows the state it represents, with no way back except undo. A third composition also matches how the result is used: A and B are boards, A → B is a shot.

Arriving layers are cloned into the transition — subtree, components and keyframes — rather than referenced. A reference would tie the transition to later edits of the target board, which is the opposite of what a baked transition is for.

When nothing matches#

You get a cross-fade, and the toast says so explicitly: "Nothing matched — layers pair up by name, so give the elements the same names in both boards." A transition that silently dissolves looks like the feature is broken; naming the cause makes it a two-second fix.

Layout#

core/animation/
  layerMatch.ts           pure: which layer is which
  smartAnimate.ts         pure: what to write, and what not to
  smartAnimateApply.ts    the graph, the duplicate, the clones
  smartAnimateCommands.ts one command per target composition

The first two are pure — descriptors and values in, plans out — so the correspondence and the restraint are tested exhaustively without a scene graph.

There is one command per target composition rather than a dialog, so the feature is reachable by typing a board's name into the palette. Boards get created and renamed while the app runs and buildStaticCommands runs once at boot, so the set is kept in step by a subscription (installSmartAnimateCommandSync) rather than snapshotted — otherwise a board made after startup would have no command to animate to it.

Two things about that list are easy to get wrong, and both were found by running it rather than by a test:

• The excluded placeholder is pristine AND layerless. The default composition keeps pristine: true forever — nothing clears it when layers are added — so filtering on the flag alone hides the composition most people put their first board in. pristineCompToAdopt already states the correct rule: "a pristine comp the user has already drawn into is theirs by use".
• The sync key is the active COMPOSITION, not the active tab. A tab can be pointed at a different comp without its id changing, and the active comp is the one excluded from its own target list — so keying on the tab left the commands offering whichever board happened to be open when they were last built.