gsap-scrolltrigger

GSAP ScrollTrigger

由滚动驱动的动画和交互。

快速入门

npm install gsap

import gsap from 'gsap';
import { ScrollTrigger } from 'gsap/ScrollTrigger';

gsap.registerPlugin(ScrollTrigger);

gsap.to('.box', {
  x: 500,
  scrollTrigger: {
    trigger: '.box',
    start: 'top center',
    end: 'bottom center',
    scrub: true
  }
});

核心概念

基本 ScrollTrigger

gsap.to('.element', {
  x: 200,
  scrollTrigger: {
    trigger: '.element',  // Element that triggers the animation
    start: 'top center',  // When trigger hits viewport center
    end: 'bottom center', // When trigger leaves viewport center
    toggleActions: 'play pause resume reset'
  }
});

起始／结束位置

// Format: "trigger-position viewport-position"
start: 'top center'      // Trigger's top hits viewport center
start: 'top 80%'         // Trigger's top hits 80% down viewport
start: 'center center'   // Trigger's center hits viewport center
start: 'bottom top'      // Trigger's bottom hits viewport top
start: 'top top+=100'    // Trigger's top hits 100px below viewport top

位置参考

值	描述
top	顶部边缘
center	中心
bottom	底部边缘
80%	距顶部 80%
+=100	加 100 像素
-=50	减 50 像素

Scrub 动画

基本 Scrub

// Animation progress tied to scroll position
gsap.to('.progress-bar', {
  scaleX: 1,
  scrollTrigger: {
    trigger: '.content',
    start: 'top top',
    end: 'bottom bottom',
    scrub: true  // Directly linked to scroll
  }
});

平滑 Scrub

gsap.to('.element', {
  x: 500,
  scrollTrigger: {
    trigger: '.section',
    scrub: 1,    // 1 second smoothing
    // scrub: 0.5  // 0.5 second smoothing
    // scrub: 2    // 2 second smoothing (laggy feel)
  }
});

使用时间轴的 Scrub

const tl = gsap.timeline({
  scrollTrigger: {
    trigger: '.container',
    start: 'top top',
    end: '+=3000',  // Scroll distance
    scrub: 1,
    pin: true
  }
});

tl.to('.step1', { opacity: 1 })
  .to('.step2', { opacity: 1 })
  .to('.step3', { opacity: 1 });

固定

基本固定

ScrollTrigger.create({
  trigger: '.panel',
  start: 'top top',
  end: '+=500',      // Pin for 500px of scroll
  pin: true
});

带动画的固定

gsap.to('.content', {
  x: '-200%',
  ease: 'none',
  scrollTrigger: {
    trigger: '.horizontal-section',
    start: 'top top',
    end: () => '+=' + document.querySelector('.horizontal-section').offsetWidth,
    pin: true,
    scrub: 1
  }
});

固定间距

ScrollTrigger.create({
  trigger: '.section',
  pin: true,
  pinSpacing: true,   // Default: adds space for pinned duration
  // pinSpacing: false  // No extra space (content overlaps)
  // pinSpacing: '500px' // Custom spacing
});

切换操作

操作语法

// Format: "onEnter onLeave onEnterBack onLeaveBack"
toggleActions: 'play pause resume reset'

// Common combinations:
toggleActions: 'play none none none'     // Play once
toggleActions: 'play reverse play reverse' // Toggle direction
toggleActions: 'restart none none none'  // Restart each time
toggleActions: 'play complete reverse reset'

操作值

操作	效果
play	向前播放
pause	暂停
resume	从暂停处继续
reverse	向后播放
restart	从头重新开始
reset	重置到起点（不播放动画）
complete	跳到末尾
none	不执行任何操作

吸附点

基本吸附

ScrollTrigger.create({
  trigger: '.sections',
  start: 'top top',
  end: 'bottom bottom',
  snap: 1 / 4  // Snap to quarters
});

吸附到标签

const tl = gsap.timeline({
  scrollTrigger: {
    trigger: '.container',
    scrub: 1,
    snap: {
      snapTo: 'labels',
      duration: 0.5,
      ease: 'power2.inOut'
    }
  }
});

tl.addLabel('intro')
  .to('.a', { opacity: 1 })
  .addLabel('middle')
  .to('.b', { opacity: 1 })
  .addLabel('end');

吸附配置

snap: {
  snapTo: [0, 0.25, 0.5, 0.75, 1],  // Snap to specific points
  duration: { min: 0.2, max: 0.6 }, // Snap duration range
  delay: 0,                          // Delay before snap
  ease: 'power1.inOut',             // Snap easing
  directional: true                  // Snap in scroll direction
}

回调

ScrollTrigger 回调

ScrollTrigger.create({
  trigger: '.section',
  onEnter: () => console.log('Entered'),
  onLeave: () => console.log('Left'),
  onEnterBack: () => console.log('Entered from bottom'),
  onLeaveBack: () => console.log('Left going up'),
  onUpdate: (self) => console.log('Progress:', self.progress),
  onToggle: (self) => console.log('Active:', self.isActive),
  onRefresh: () => console.log('Refreshed')
});

基于进度的更新

ScrollTrigger.create({
  trigger: '.section',
  start: 'top bottom',
  end: 'bottom top',
  onUpdate: (self) => {
    // self.progress: 0 to 1
    // self.direction: 1 (down) or -1 (up)
    // self.velocity: scroll speed
    updateElement(self.progress);
  }
});

视差效果

基本视差

// Background moves slower than scroll
gsap.to('.background', {
  yPercent: -50,
  ease: 'none',
  scrollTrigger: {
    trigger: '.section',
    scrub: true
  }
});

// Foreground moves faster
gsap.to('.foreground', {
  yPercent: 50,
  ease: 'none',
  scrollTrigger: {
    trigger: '.section',
    scrub: true
  }
});

多层视差

const layers = [
  { selector: '.layer-1', speed: -20 },
  { selector: '.layer-2', speed: -40 },
  { selector: '.layer-3', speed: -60 },
  { selector: '.layer-4', speed: -80 }
];

layers.forEach(layer => {
  gsap.to(layer.selector, {
    yPercent: layer.speed,
    ease: 'none',
    scrollTrigger: {
      trigger: '.parallax-section',
      start: 'top bottom',
      end: 'bottom top',
      scrub: true
    }
  });
});

水平滚动

水平区段

const sections = gsap.utils.toArray('.panel');

gsap.to(sections, {
  xPercent: -100 * (sections.length - 1),
  ease: 'none',
  scrollTrigger: {
    trigger: '.horizontal-container',
    pin: true,
    scrub: 1,
    snap: 1 / (sections.length - 1),
    end: () => '+=' + document.querySelector('.horizontal-container').offsetWidth
  }
});

标记（开发）

ScrollTrigger.create({
  trigger: '.section',
  start: 'top center',
  end: 'bottom center',
  markers: true,  // Show visual markers
  // markers: { startColor: 'green', endColor: 'red', fontSize: '12px' }
});

批量动画

滚动时交错显示

ScrollTrigger.batch('.card', {
  onEnter: (elements) => {
    gsap.from(elements, {
      opacity: 0,
      y: 50,
      stagger: 0.1,
      duration: 0.5
    });
  },
  start: 'top 85%'
});

批量配置

ScrollTrigger.batch('.item', {
  interval: 0.1,  // Time between batches
  batchMax: 3,    // Max items per batch
  onEnter: batch => gsap.to(batch, { opacity: 1, y: 0, stagger: 0.1 }),
  onLeave: batch => gsap.to(batch, { opacity: 0, y: 20 }),
  onEnterBack: batch => gsap.to(batch, { opacity: 1, y: 0 }),
  onLeaveBack: batch => gsap.to(batch, { opacity: 0, y: -20 })
});

常见模式

滚动时显示

gsap.utils.toArray('.reveal').forEach(elem => {
  gsap.from(elem, {
    opacity: 0,
    y: 50,
    duration: 0.8,
    scrollTrigger: {
      trigger: elem,
      start: 'top 80%',
      toggleActions: 'play none none none'
    }
  });
});

进度指示器

gsap.to('.progress-bar', {
  scaleX: 1,
  transformOrigin: 'left center',
  ease: 'none',
  scrollTrigger: {
    trigger: 'body',
    start: 'top top',
    end: 'bottom bottom',
    scrub: 0.3
  }
});

粘性页眉变换

ScrollTrigger.create({
  start: 'top -80',
  onUpdate: (self) => {
    if (self.direction === 1) {
      gsap.to('.header', { y: -80, duration: 0.3 });
    } else {
      gsap.to('.header', { y: 0, duration: 0.3 });
    }
  }
});

时间坍缩模式

倒计时滚动显示

// Reveal countdown sections as user scrolls
const sections = ['days', 'hours', 'minutes', 'seconds'];

sections.forEach((section, i) => {
  gsap.from(`.countdown-${section}`, {
    opacity: 0,
    scale: 0.8,
    y: 50,
    duration: 0.8,
    ease: 'power3.out',
    scrollTrigger: {
      trigger: `.countdown-${section}`,
      start: 'top 80%',
      toggleActions: 'play none none none'
    }
  });
});

基于滚动的时间膨胀效果

gsap.timeline({
  scrollTrigger: {
    trigger: '.time-section',
    start: 'top center',
    end: 'bottom center',
    scrub: 1
  }
})
.to('.time-digit', {
  textShadow: '0 0 50px #00F5FF, 0 0 100px #00F5FF',
  scale: 1.1
})
.to('.particles', {
  opacity: 1,
  filter: 'blur(0px)'
}, '<');

性能提示

// Disable on mobile if needed
ScrollTrigger.matchMedia({
  '(min-width: 768px)': function() {
    // Desktop animations
  },
  '(max-width: 767px)': function() {
    // Simpler mobile animations
  }
});

// Refresh on resize
ScrollTrigger.refresh();

// Kill all ScrollTriggers
ScrollTrigger.killAll();

// Kill specific trigger
const st = ScrollTrigger.create({ ... });
st.kill();

参考

• 动画基础请参见 gsap-fundamentals
• 时间轴组合请参见 gsap-sequencing
• ScrollTrigger 的 React 集成请参见 gsap-react