Expressions
How Prism writes working After Effects expressions — inertial bounce, wiggle, loops — while animation comes back as editable keyframes by default.
Expressions are the right tool for some motion and the wrong tool for most of it. Prism writes them when behavior should be procedural — an inertial bounce, a wiggle, a loop that keeps running — and otherwise returns plain, editable keyframes. Either way, what lands in your composition is a working After Effects expression you didn't have to paste or debug.
Keyframes first, expressions when they earn it
The default output of Prism's animation tools is keyframes — the same objects you'd set by hand, on the same properties, fully editable in the Graph Editor. That keeps your timeline legible and lets you tweak timing without reading code.
An expression is the better answer only when the motion is a rule rather than a fixed path. Ask for follow-through after a move and you want an inertial bounce that reacts to the keyframes; ask for idle life on a layer and you want a wiggle — gentle, never-repeating random movement; ask for a seamless cycle and you want a loop (in After Effects, a loopOut expression that repeats the keyframes). These don't want to be baked into keyframes — they want to stay procedural. Prism picks the expression in those cases and the keyframes everywhere else.
If you'd rather have keyframes you can scrub and reshape, say so — Prism will bake the motion instead of leaving an expression on the property.
What lands on the property
Prism writes the expression, checks it, and applies it to the property for you, so you never paste a snippet from a chat window — the output is editable AE motion, not a script (why that matters). Open the property to read or edit the expression like one you wrote yourself.
| You say | Prism does / writes | Stays procedural |
|---|---|---|
| "Add natural follow-through so the card keeps a little bounce after it lands" | An inertial-bounce expression on Position that reacts to the existing keyframes | Yes |
| "Give the background a slow, subtle drift" | A wiggle expression on Position with gentle amount and frequency | Yes |
| "Loop this spin forever" | A loop expression on Rotation | Yes |
| "Make the shadow follow the icon's position" | A linking expression tying one property to another | Yes |
| "Just move it from A to B and ease out" | Plain, editable keyframes | No |
If an expression can't reference a layer: when the layer or property it needs isn't in the comp, Prism tells you what it couldn't find instead of leaving a broken expression that errors on the first frame, so you can re-ask with the right target.
The decision itself comes from reading your composition: Prism works against the real layers, properties, and existing keyframes in your active comp, then chooses a path (keyframes) or a rule (expression). That read-and-write loop is described in how Prism works.
Notes and limits
Related
- Real keyframes, not scripts — why the output is editable motion, not code.
- Lifelike motion — anticipation, follow-through, overshoot, and settle.
- Compositions — the active comp is the context Prism reads against.
- How Prism works — the read, reason, write loop and reversibility.
Effects
Apply and configure After Effects effects and presets in plain language with Prism — native, editable controls, undoable in one step, with honest re-run handling.
Timeline
Retime layers, set in and out points, and add comp or layer markers in After Effects through Prism — frame-accurate timing you can pair with beat markers for music sync.