Smear stretch

When to use

Use when a cut should feel elastic and fast, like an animator's smear frame: shot A's content stretches toward the exit on carry until it is streaks of its own colours, the cut lands at the peak, and shot B's content arrives as the same streak from the other side and snaps back to shape on pop. The detail that sells it is volume: the content thins as it stretches (scaleY 0.9) and bulges a few percent as the pop passes rest (scaleX 0.91, scaleY 1.08), so it reads as rubber, not as a scaled picture. Clip: smear-stretch.mp4. Demo: demo/smear-stretch.html.

The code

<svg width="0" height="0" style="position: absolute"><filter id="smear" x="-5%" width="110%"><feGaussianBlur id="mb" stdDeviation="0 0"/></filter></svg>
<div class="shot b"><div class="fg" style="transform-origin: 100% 50%; filter: url(#smear)">...</div></div>
<div class="shot a"><div class="fg" style="transform-origin: 0 50%; filter: url(#smear)">...</div></div>
<script type="module">
import '../../core/engine/page-api.js';
import { easeFn } from '../../core/motion/presets.js';
const clamp = (u) => Math.min(1, Math.max(0, u));
const OUT = 0.5, OUT_DUR = 0.16, IN_DUR = 0.62, PEAK = 9, carry = easeFn('carry'), pop = easeFn('pop');
const cut = OUT + OUT_DUR;
const stretch = (t) => (t < cut ? carry(clamp((t - OUT) / OUT_DUR)) : 1 - pop(clamp((t - cut) / IN_DUR)));
vawe.onFrame((t) => {
  const s = stretch(t);
  const sx = s > 0 ? 1 + (PEAK - 1) * s : 1 + 0.6 * s, sy = s > 0 ? 1 - 0.1 * Math.min(1, s * 1.5) : 1 - 0.5 * s;
  a.style.visibility = t < cut ? 'visible' : 'hidden';
  (t < cut ? fa : fb).style.transform = `scale(${sx}, ${sy})`;   // fa, fb: the .fg of each shot
  blur.setAttribute('stdDeviation', `${Math.abs(stretch(t + 1 / 60) - s) * PEAK * 14} 0`);
});
</script>

Easing and timing

The clip runs 1.4 s. The look is daylight.

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

Stretch the content, never the shot's ground: a ground squashed below full width shows a gap at the edge. The two origins are opposite (A anchored at its left, B at its right), so the streak runs one way through the cut. A peak of 8 to 10x turns type into clean streaks; under 5x it reads as a distorted word. EASE.pop passes rest once by about 15 percent; scale that undershoot by 0.6 so the squash is a few percent, since the full stretch factor makes it a bounce. Exit 0.16 s, entrance 0.62 s.

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

Sound

Sound: none; the streak already says speed, and the film keeps its one whoosh for a whip.