Split reveal

When to use

Use when the next shot is behind the current one and the current one should open like a pair of doors. Shot A is drawn twice, each copy showing one half, so the seam is invisible until they part. The detail that sells it is the light in the gap: shot B waits in the dark, a shadow is cast beside each door, and B lights up and settles from 1.12x as the doors clear. Clip: split-reveal.mp4. Demo: demo/split-reveal.html.

The code

import { EASE } from '../../core/motion/presets.js';
const W = innerWidth, far = 0.62;
const t = { duration: 850, delay: 350, easing: EASE.settle, fill: 'both' };
// each .door is 50vw wide: a clipped full-width copy of shot A, plus an .edge gradient beside its inner side
left.animate([{ translate: '0 0' }, { translate: `${-W * far}px 0` }], t);
right.animate([{ translate: '0 0' }, { translate: `${W * far}px 0` }], t);
veil.animate([{ opacity: 0.85 }, { opacity: 0.8, offset: 0.4 }, { opacity: 0 }], t);   // black over shot B
shotB.animate([{ scale: 1.12 }, { scale: 1 }], { duration: 1100, delay: 350, easing: EASE.land, fill: 'both' });
// door blur: stdDeviation = 0.2 x one frame's travel, x only, set in vawe.onFrame as in push-blur

Easing and timing

The clip runs 1.6 s. The look is dusk.

The clip uses 2 named eases from core/motion/presets.js. Each is a pair of After Effects handles: influence is how far along the segment the handle reaches, and speed is how fast the value moves at the key, as a multiple of the segment's average speed. Motion in the docs explains both.

Notes

The doors travel 62 percent of the width, not 50: the shadow beside each door must also leave the frame, or a grey band stays on screen after the move. Keep the veil dark until the gap is wide (the 0.4 offset), or B is lit before it is uncovered and the gap reads as a hole. EASE.settle moves the doors fastest through the middle; a plain ease-in-out spends the move in two frames. No highlight line on the door edge: it reads as a border while the doors are still shut.

Looks (ground, type, radius, accent) live in demo/demo.css; this snippet keeps neutral tokens.

Sound

Sound: none; the light in the gap is the event, and it stays quiet.