Scroll Cinema

Generate premium scrollytelling websites where scroll is the narrative engine. Three libraries coordinate as a unified system: Lenis provides buttery smooth locomotion, GSAP ScrollTrigger orchestrates cinematic section reveals with fluid color transitions, and Three.js renders a living painted-texture background that reacts to cursor position and scroll progress.

This is NOT a general animation skill, a 3D product viewer, or a scroll-hijacking pattern. Scroll-cinema produces pages where the reader moves through chapters — each chapter entrance is choreographed, the color palette flows between sections, and an ambient shader canvas breathes behind the content.

Quick Start

# Complete cinematic storytelling site
python3 ~/.claude/skills/scroll-cinema/scripts/scroll_cinema_generator.py \
  --mode full-cinema \
  --shader painted-dots \
  --chapters 5 \
  --pacing medium \
  --output story.html

# Chapter reveals with color transitions (no Three.js)
python3 ~/.claude/skills/scroll-cinema/scripts/scroll_cinema_generator.py \
  --mode chapter-reveal \
  --chapters 4 \
  --output chapters.html

# Standalone reactive shader background
python3 ~/.claude/skills/scroll-cinema/scripts/scroll_cinema_generator.py \
  --mode painted-backdrop \
  --shader watercolor \
  --output backdrop.html

# All three shader presets side by side
python3 ~/.claude/skills/scroll-cinema/scripts/scroll_cinema_generator.py \
  --mode catalog \
  --output catalog.html

Or describe a concept and let Claude generate directly from the templates and references.

Example: /scroll-cinema a story about the Mediterranean told in five chapters — from dawn on the Aegean to dusk on the Strait of Sicily

Modes

Core Architecture

┌──────────────┐     autoRaf: false      ┌─────────────────┐
│    Lenis     │ ──── lenis.raf(time) ──→ │   GSAP Ticker   │
│ (smooth DOM  │ ←── drives animation ─── │ (master clock)  │
│  scrolling)  │                          └────────┬────────┘
└──────┬───────┘                                   │
       │                                    ┌──────▼──────┐
       │ lenis.on('scroll')                 │ ScrollTrigger│
       │ → ScrollTrigger.update()           │ (orchestrate │
       │                                    │  sections)   │
       │                                    └──────┬───────┘
       │                                           │
       │  scroll progress                          │ drives
       │  + cursor position                        │
       ▼                                           ▼
┌──────────────┐                          ┌────────────────┐
│  Three.js    │                          │ Section Reveals │
│  Shader      │ ← uniforms: uScroll,    │ Color Interp.   │
│  Background  │   uMouse, uTime         │ Typography Anim │
└──────────────┘                          └────────────────┘

Non-negotiable initialization sequence — the single most important pattern in this skill:

// 1. Register GSAP plugins FIRST
gsap.registerPlugin(ScrollTrigger);

// 2. Init Lenis with autoRaf OFF — GSAP drives the loop
const lenis = new Lenis({ autoRaf: false });

// 3. Connect Lenis to GSAP ticker (single animation frame)
gsap.ticker.add((time) => {
  lenis.raf(time * 1000); // GSAP=seconds, Lenis=ms
});
gsap.ticker.lagSmoothing(0);

// 4. Sync ScrollTrigger with Lenis scroll position
lenis.on('scroll', ScrollTrigger.update);

Full integration details, cleanup, and SPA lifecycle: references/lenis-gsap-integration.md

Shader Presets

All shaders receive these uniforms from the orchestration layer:

• uTime — elapsed time from GSAP ticker
• uMouse — normalized cursor position, lerped at 0.08 for smoothness
• uScroll — Lenis smoothed scroll progress (0.0–1.0), lerped at 0.05
• uVelocity — scroll velocity magnitude (0.0–1.0), clamped ±3 then normalized, lerped at 0.10
• uChapter — smooth chapter index float, lerped at 0.03
• uMobile — 1.0 on viewports ≤768px, 0.0 otherwise (watercolor uses this to skip edge detection)
• uResolution — viewport dimensions for aspect correction
• uChapterHue / uChapterLightness — chapter color sync, lerped at 0.03

Full GLSL code, uniform pipeline, and lerp rates: references/painted-shader-patterns.md

Color System

Scroll-driven color transitions between chapters using OKLCH interpolation. sRGB interpolation produces muddy brown midpoints when transitioning between hues — OKLCH maintains perceptual uniformity.

Each chapter defines a palette via data attributes:

<section data-chapter="0" data-hue="250" data-chroma="0.15" data-lightness="0.25">

GSAP ScrollTrigger tweens CSS custom properties registered via @property for GPU-accelerated animation. Fallback to HSL interpolation where OKLCH is unsupported.

Full color system, @property registration, fallback strategy: references/color-interpolation.md

Cinematic Easings

Four custom easing curves for scroll-driven cinematic animation:

Timing philosophy and ScrollTrigger scrub values: references/cinematic-easings.md

Composition Parameters

Chapter Structure

Each chapter is a <section> element with sticky content. Minimum height scales with pacing. Entrance animations complete within the first 30% of the chapter's scroll distance — the reader never waits.

Section entrance patterns: fade-up (default), split-text, scale-reveal, clip-path-wipe.

Full chapter architecture, scroll pacing table, responsive layout: references/chapter-structure.md Design tokens (colors, typography, spacing, animation): references/design-tokens.md

Gotchas — What Claude Gets Wrong Without This Skill

1. Initializes Lenis with autoRaf: true alongside GSAP. Causes dual animation loops, stuttering, incorrect trigger firing. Must set autoRaf: false and let GSAP drive.
2. Interpolates chapter colors in sRGB. Produces muddy brown midpoints. Must use OKLCH or at minimum HSL.
3. Feeds raw scroll position to Three.js shaders. Produces jerky backgrounds. Must lerp the scroll value (rate 0.05).
4. Creates separate requestAnimationFrame loops for Three.js and GSAP. Must share a single tick via gsap.ticker.add().
5. Uses ScrollSmoother instead of Lenis. ScrollSmoother requires GSAP Club (paid). Lenis is free and equivalent.
6. Uses default GSAP easings. They feel robotic for cinematic scroll. Must define cinematicSilk/Smooth/Flow/Linear custom curves.
7. Animates CSS background-color per section. Expensive repaint. Must use CSS custom properties with @property for GPU acceleration.
8. Forgets cleanup in SPA contexts. Lenis, ScrollTrigger, and Three.js all need explicit .destroy() on unmount.
9. Uses position: fixed for the Three.js canvas inside the Lenis scroll wrapper. Fixed-position children inside a transformed parent resolve relative to the parent. Canvas must be a sibling of (not child of) the scroll content wrapper.
10. Puts text content inside the Three.js scene. Text should be HTML overlay — Three.js is background only. Content must be accessible without WebGL.
11. Omits prefers-reduced-motion. Must disable all animation, show final states, revert Lenis to native scroll.
12. Leaves will-change on permanently. GPU memory leak. Add before animation, remove after completion.
13. Missing gsap.ticker.lagSmoothing(0). Causes visible jumps in Lenis's smooth interpolation during lag frames.

Full anti-pattern catalog with wrong/right code examples: references/anti-patterns.md

Implementation Rules

1. Vanilla only. No React, Vue, Svelte. Plain HTML + CSS + JS. CDN imports for Three.js, GSAP, Lenis.
2. Single-file output. Everything in one HTML file. CDN imports only.
3. Single animation loop. GSAP ticker drives everything — Lenis, ScrollTrigger, Three.js render. No separate rAF.
4. performance.now() for timing. Never Date.now() in animation loops.
5. prefers-reduced-motion required. Every animated effect shows final state immediately. Shader animation freezes. Lenis reverts to native scroll.
6. Semantic HTML chapters. <section> with headings, readable without JS. Three.js canvas is aria-hidden="true".
7. OKLCH color interpolation with sRGB/HSL fallback. Never animate background-color directly — use @property-registered custom properties.
8. --sc-* token prefix for all CSS custom properties. Never hardcode colors or timing.
9. Lerped shader uniforms. Never feed raw values — smooth with lerp at rates defined in design tokens.
10. Device pixel ratio capped at 2.0 on desktop, 1.5 on mobile. Math.min(window.devicePixelRatio, isMobile ? 1.5 : 2.0).
11. Viewport meta required. <meta name="viewport" content="width=device-width, initial-scale=1">.
12. Resize handler. Update renderer size, resolution uniform, camera aspect. Debounced 80ms. Call setPixelRatio() before setSize() to avoid double framebuffer allocation.
13. Single global export. window.__scCleanup is the sole intentional global — a cleanup function for SPA integration. All other state lives in module scope.

Cross-Skill Relationships

• threejs-particle-canvas: scroll-cinema's painted backdrop produces the background canvas. threejs-particle-canvas produces ambient contemplative experiences. If scroll drives the narrative → scroll-cinema. If the canvas IS the experience → threejs-particle-canvas.
• conductor-motion: conductor-motion owns behavioral simulations (typewriter, progress bars). Scroll-cinema owns cinematic section choreography. A scroll-cinema page may embed conductor-motion patterns within individual sections.
• rocaille-shader: rocaille-shader's domain warping GLSL serves as the domain-warp preset upstream. Scroll-cinema orchestrates it with scroll. If standalone shader art → rocaille-shader. If scroll-driven background → scroll-cinema.
• grainient: grainient owns CSS surface effects (shadows, glass, aurora). Scroll-cinema owns scroll-driven orchestration. A scroll-cinema page may use grainient palettes. No overlap — grainient is 2D CSS, scroll-cinema is the 3D+scroll orchestration layer.
• shape / design-md: Upstream. .design-context.md and DESIGN.md feed color palette and typography into scroll-cinema. If .design-context.md exists with MOTION_INTENSITY dial, derive pacing from it (1-3 → slow, 4-6 → medium, 7-10 → fast).

CDN Versions

Pin these versions for stability:

<!-- Lenis 1.2.3 -->
<script src="https://unpkg.com/lenis@1.2.3/dist/lenis.min.js"></script>
<link rel="stylesheet" href="https://unpkg.com/lenis@1.2.3/dist/lenis.css">

<!-- GSAP 3.12 + ScrollTrigger + CustomEase -->
<script src="https://cdn.jsdelivr.net/npm/gsap@3.12/dist/gsap.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/gsap@3.12/dist/ScrollTrigger.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/gsap@3.12/dist/CustomEase.min.js"></script>

<!-- Three.js r170 -->
<script type="importmap">
{
  "imports": {
    "three": "https://cdn.jsdelivr.net/npm/three@0.170.0/build/three.module.js"
  }
}
</script>

References

Load on-demand when implementing specific aspects:

Validation

python3 ~/.claude/skills/scroll-cinema/scripts/validate_scroll_cinema.py output.html

Checks: Lenis CDN, GSAP CDN, Three.js CDN (if applicable), autoRaf: false, gsap.ticker.add with lenis.raf, ScrollTrigger.update in scroll callback, prefers-reduced-motion media query, aria-hidden on canvas, no setInterval for animation, viewport meta, no transition: all, semantic section elements, --sc-* custom properties, no standalone requestAnimationFrame, no raw scroll in uniforms, no direct backgroundColor animation, SRI integrity hashes, cleanup function, scroll-driven entrance animations with toggleActions, entrance reduced-motion gating.