Add web animation skills (iart-ai/web-animation-skills)
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01GYeokZtSmqg42ZGWsLXX2C
This commit is contained in:
42 files changed
+4170
No files matched your search
@@ -0,0 +1,255 @@
|
||||
# ScrollTrigger + Lenis / Locomotive smooth-scroll sync
|
||||
|
||||
Wire GSAP ScrollTrigger together with Lenis (or Locomotive) smooth scrolling so there is no jitter, no marker drift, no broken pins, and no flipped/laggy scroll direction. Every one of those bugs has the same root cause: two animation loops running independently. Lenis transforms the scroll position on its own `requestAnimationFrame` loop while ScrollTrigger reads scroll on GSAP's ticker — when they tick separately, ScrollTrigger samples a stale position and everything desyncs. The fix is to run one loop: let GSAP's ticker drive Lenis, and tell ScrollTrigger to update on every Lenis scroll.
|
||||
|
||||
## The one canonical wiring (Lenis)
|
||||
|
||||
This is the entire correct setup. Do not add a separate `requestAnimationFrame` loop for Lenis — that is the most common mistake and the source of nearly all desync.
|
||||
|
||||
```js
|
||||
import Lenis from 'lenis';
|
||||
import gsap from 'gsap';
|
||||
import { ScrollTrigger } from 'gsap/ScrollTrigger';
|
||||
|
||||
gsap.registerPlugin(ScrollTrigger);
|
||||
|
||||
const lenis = new Lenis({
|
||||
duration: 1.2,
|
||||
smoothWheel: true,
|
||||
// do NOT enable Lenis's own rAF; GSAP's ticker drives it (below)
|
||||
});
|
||||
|
||||
// 1. Update ScrollTrigger every time Lenis scrolls
|
||||
lenis.on('scroll', ScrollTrigger.update);
|
||||
|
||||
// 2. Drive Lenis from GSAP's ticker (single shared loop).
|
||||
// gsap.ticker time is in SECONDS; Lenis expects MILLISECONDS.
|
||||
gsap.ticker.add((time) => {
|
||||
lenis.raf(time * 1000);
|
||||
});
|
||||
|
||||
// 3. Disable GSAP's lag smoothing so ScrollTrigger never defers/
|
||||
// catches up against Lenis (prevents jitter on heavy frames)
|
||||
gsap.ticker.lagSmoothing(0);
|
||||
```
|
||||
|
||||
Three lines do all the work:
|
||||
|
||||
1. `lenis.on('scroll', ScrollTrigger.update)` — ScrollTrigger recomputes positions the instant Lenis moves the page, so triggers/markers/pins track the smoothed scroll exactly.
|
||||
2. `gsap.ticker.add(time => lenis.raf(time * 1000))` — Lenis advances inside GSAP's loop, guaranteeing both run on the same frame and in the same order. Critical unit conversion: `gsap.ticker` passes seconds, `lenis.raf()` wants milliseconds, so multiply by 1000.
|
||||
3. `gsap.ticker.lagSmoothing(0)` — disables GSAP's catch-up behavior that, combined with Lenis, causes visible jitter when a frame is slow.
|
||||
|
||||
After this, never call `requestAnimationFrame(raf)` for Lenis yourself. If any tutorial code has a standalone `function raf(time){ lenis.raf(time); requestAnimationFrame(raf) }` loop, delete it — it competes with the ticker and reintroduces jitter and direction lag.
|
||||
|
||||
## Locomotive Scroll variant
|
||||
|
||||
Locomotive needs `scrollerProxy` because it scrolls an inner element, not `window`. The principle is identical (one loop, update ScrollTrigger on scroll), but the proxy maps coordinates:
|
||||
|
||||
```js
|
||||
const locoScroll = new LocomotiveScroll({
|
||||
el: document.querySelector('[data-scroll-container]'),
|
||||
smooth: true,
|
||||
});
|
||||
|
||||
locoScroll.on('scroll', ScrollTrigger.update);
|
||||
|
||||
ScrollTrigger.scrollerProxy('[data-scroll-container]', {
|
||||
scrollTop(value) {
|
||||
return arguments.length
|
||||
? locoScroll.scrollTo(value, { duration: 0, disableLerp: true })
|
||||
: locoScroll.scroll.instance.scroll.y;
|
||||
},
|
||||
getBoundingClientRect() {
|
||||
return { top: 0, left: 0, width: innerWidth, height: innerHeight };
|
||||
},
|
||||
pinType: document.querySelector('[data-scroll-container]').style.transform
|
||||
? 'transform' : 'fixed',
|
||||
});
|
||||
|
||||
ScrollTrigger.addEventListener('refresh', () => locoScroll.update());
|
||||
ScrollTrigger.refresh();
|
||||
```
|
||||
|
||||
Every ScrollTrigger then needs `scroller: '[data-scroll-container]'`. Lenis is simpler because it scrolls the real document, so no `scrollerProxy` is needed.
|
||||
|
||||
## Pins, refresh, and resize
|
||||
|
||||
- Pinned ScrollTriggers work without `scrollerProxy` under Lenis because Lenis scrolls the document body. If pins still jump, ensure no rogue rAF loop exists and that `ScrollTrigger.update` is wired.
|
||||
- On dynamic content/resize, call `ScrollTrigger.refresh()` after layout settles. With Lenis, also call `lenis.resize()` if container size changes.
|
||||
- For elements that should *not* be smoothed (e.g. a modal that scrolls natively), mark with `data-lenis-prevent` so Lenis ignores them.
|
||||
|
||||
## Anchor links with smooth scroll
|
||||
|
||||
Native `<a href="#section">` jumps bypass Lenis (instant jump, then Lenis fights it). Route anchors through `lenis.scrollTo`:
|
||||
|
||||
```js
|
||||
document.querySelectorAll('a[href^="#"]').forEach((a) => {
|
||||
a.addEventListener('click', (e) => {
|
||||
const id = a.getAttribute('href');
|
||||
if (id.length > 1) {
|
||||
e.preventDefault();
|
||||
lenis.scrollTo(id, { offset: 0 }); // accepts selector, element, or number
|
||||
}
|
||||
});
|
||||
});
|
||||
```
|
||||
|
||||
If a sticky header overlaps the target, pass a negative offset or an offset callback:
|
||||
|
||||
```js
|
||||
lenis.scrollTo(targetEl, { offset: -80 }); // 80px sticky header
|
||||
```
|
||||
|
||||
## Reduced-motion gate
|
||||
|
||||
Respect `prefers-reduced-motion`: skip smooth scrolling entirely (do not instantiate Lenis, or stop it) and let ScrollTrigger run on native scroll.
|
||||
|
||||
```js
|
||||
const prefersReduced = matchMedia('(prefers-reduced-motion: reduce)').matches;
|
||||
|
||||
let lenis;
|
||||
if (!prefersReduced) {
|
||||
lenis = new Lenis({ duration: 1.2 });
|
||||
lenis.on('scroll', ScrollTrigger.update);
|
||||
gsap.ticker.add((time) => lenis.raf(time * 1000));
|
||||
gsap.ticker.lagSmoothing(0);
|
||||
}
|
||||
// ScrollTrigger animations are defined normally and work with or without Lenis
|
||||
```
|
||||
|
||||
## Cleanup (SPA / React / route changes)
|
||||
|
||||
Destroy Lenis and remove the ticker callback on unmount, or stacked loops accumulate:
|
||||
|
||||
```js
|
||||
function setup() {
|
||||
const update = (time) => lenis.raf(time * 1000);
|
||||
lenis.on('scroll', ScrollTrigger.update);
|
||||
gsap.ticker.add(update);
|
||||
gsap.ticker.lagSmoothing(0);
|
||||
return () => {
|
||||
gsap.ticker.remove(update);
|
||||
lenis.destroy();
|
||||
ScrollTrigger.getAll().forEach((t) => t.kill());
|
||||
};
|
||||
}
|
||||
```
|
||||
|
||||
## Debugging checklist (work top to bottom)
|
||||
|
||||
1. **Is there a rogue rAF loop?** Search the codebase for `requestAnimationFrame` near `lenis.raf`. If Lenis is also driven by `gsap.ticker`, delete the standalone loop. Two loops = jitter, lag, flipped feel.
|
||||
2. **Unit conversion present?** Confirm `lenis.raf(time * 1000)` inside the ticker. Missing `* 1000` makes scroll feel stuck or wildly slow.
|
||||
3. **Is `ScrollTrigger.update` subscribed?** `lenis.on('scroll', ScrollTrigger.update)` must exist. Without it, markers and triggers drift behind the smoothed position.
|
||||
4. **Is `lagSmoothing(0)` set?** Without it, heavy frames cause GSAP to "catch up", visible as jitter.
|
||||
5. **Markers on for diagnosis.** Add `markers: true` to a trigger. If markers sit at the *native* scroll position but content moves with smoothed scroll, the update subscription is missing or a proxy is mis-set.
|
||||
6. **Pins jumping?** Confirm no proxy is set for Lenis (it scrolls the document). For Locomotive, confirm `pinType` and `scroller` are correct.
|
||||
7. **After dynamic content / fonts / images load**, call `ScrollTrigger.refresh()`. Stale measurements cause triggers to fire at wrong offsets.
|
||||
8. **Nested scroll areas** (modals, code blocks) misbehave? Add `data-lenis-prevent` to the scrollable child.
|
||||
9. **Cleanup on route change?** In SPAs, verify `gsap.ticker.remove(update)`, `lenis.destroy()`, and killing ScrollTriggers — otherwise each navigation stacks another loop.
|
||||
|
||||
## Symptom → cause table
|
||||
|
||||
| Symptom | Most likely cause |
|
||||
|---|---|
|
||||
| General jitter/stutter | Standalone rAF loop + ticker both driving Lenis |
|
||||
| Scroll stuck / barely moves | Missing `* 1000` unit conversion |
|
||||
| Markers offset from triggers | `ScrollTrigger.update` not bound to `lenis.on('scroll')` |
|
||||
| Jitter only on heavy frames | `lagSmoothing(0)` not set |
|
||||
| Pins jump / break | Proxy wrongly set under Lenis, or wrong `pinType` (Loco) |
|
||||
| Animations a frame behind | Two loops out of order; consolidate to one ticker |
|
||||
| Anchor links jump then snap back | Native `#hash` jump not routed via `lenis.scrollTo` |
|
||||
| Triggers fire at wrong scroll position | Missing `ScrollTrigger.refresh()` after content/layout change |
|
||||
| Worse after each route change | No cleanup; loops/triggers accumulating |
|
||||
| Inner scroll container won't scroll | Lenis intercepting; add `data-lenis-prevent` |
|
||||
|
||||
## Complete React integration (useGSAP)
|
||||
|
||||
```jsx
|
||||
'use client';
|
||||
import { useRef } from 'react';
|
||||
import Lenis from 'lenis';
|
||||
import gsap from 'gsap';
|
||||
import { ScrollTrigger } from 'gsap/ScrollTrigger';
|
||||
import { useGSAP } from '@gsap/react';
|
||||
|
||||
gsap.registerPlugin(ScrollTrigger, useGSAP);
|
||||
|
||||
export default function ScrollSection() {
|
||||
const root = useRef(null);
|
||||
|
||||
useGSAP(() => {
|
||||
const prefersReduced = matchMedia('(prefers-reduced-motion: reduce)').matches;
|
||||
|
||||
let lenis;
|
||||
let update;
|
||||
if (!prefersReduced) {
|
||||
lenis = new Lenis({ duration: 1.2, smoothWheel: true });
|
||||
lenis.on('scroll', ScrollTrigger.update);
|
||||
update = (time) => lenis.raf(time * 1000);
|
||||
gsap.ticker.add(update);
|
||||
gsap.ticker.lagSmoothing(0);
|
||||
}
|
||||
|
||||
gsap.to('.panel', {
|
||||
xPercent: -100,
|
||||
ease: 'none',
|
||||
scrollTrigger: {
|
||||
trigger: '.panel',
|
||||
start: 'top top',
|
||||
end: '+=1500',
|
||||
scrub: true,
|
||||
pin: true,
|
||||
// markers: true, // enable while debugging
|
||||
},
|
||||
});
|
||||
|
||||
return () => {
|
||||
if (lenis) {
|
||||
gsap.ticker.remove(update);
|
||||
lenis.destroy();
|
||||
}
|
||||
};
|
||||
}, { scope: root });
|
||||
|
||||
return (
|
||||
<div ref={root}>
|
||||
<section className="panel">…</section>
|
||||
</div>
|
||||
);
|
||||
}
|
||||
```
|
||||
|
||||
`useGSAP` auto-reverts GSAP tweens/ScrollTriggers created in its scope on unmount; the returned function additionally tears down Lenis and the ticker callback so nothing leaks across navigations.
|
||||
|
||||
## Plain useEffect equivalent
|
||||
|
||||
```jsx
|
||||
useEffect(() => {
|
||||
const lenis = new Lenis({ duration: 1.2 });
|
||||
lenis.on('scroll', ScrollTrigger.update);
|
||||
const update = (t) => lenis.raf(t * 1000);
|
||||
gsap.ticker.add(update);
|
||||
gsap.ticker.lagSmoothing(0);
|
||||
|
||||
const ctx = gsap.context(() => {
|
||||
// ...ScrollTrigger animations here...
|
||||
});
|
||||
|
||||
return () => {
|
||||
gsap.ticker.remove(update);
|
||||
lenis.destroy();
|
||||
ctx.revert();
|
||||
};
|
||||
}, []);
|
||||
```
|
||||
|
||||
## Excluding regions from smooth scroll
|
||||
|
||||
```html
|
||||
<div class="code-block" data-lenis-prevent>…natively scrollable…</div>
|
||||
```
|
||||
|
||||
`data-lenis-prevent` on a scrollable element makes Lenis ignore wheel/touch there, so inner scrolling works normally while the page stays smooth.
|
||||
|
||||
---
|
||||
Sync ScrollTrigger to smooth scroll and the timeline tracks the page perfectly. Built by **[iart.ai](https://iart.ai/?utm_source=github&utm_medium=readme&utm_campaign=web-animation-skills&utm_content=skill_footer&utm_term=gsap-web)** — the AI motion agent for editable, on-brand motion graphics.
|
||||
Reference in new issue
Block a user