烟圈（smoke ring）

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示例

HTML

<div class="app">
<canvas id="c"></canvas>
<svg id="s" viewBox="0 0 600 600" xmlns="http://www.w3.org/2000/svg" preserveAspectRatio="xMidYMid meet" stroke="#fff" fill="none">
  <defs>
    <mask id="m1">
      <rect fill="#fff" width="100%" height="100%"/>
      <circle fill="#000" cx="300" cy="300" r="285"/>
    </mask>
    <mask id="m2">
      <rect fill="#fff" width="100%" height="100%"/>
      <circle fill="#000" cx="300" cy="300" r="272"/>
    </mask>    
  </defs>

  <circle class="ring1" cx="300" cy="300" r="210" stroke-width="220" stroke="#000" />  
  
  <g id="marks">
    <path mask="url(#m1)" opacity="0.5" d="M0.2,289.5l599.6,20.9 M6.6,237.6l586.9,124.7 M21.8,187.6l556.3,224.8 M45.6,141l508.8,318 M77.1,99.3
      L300,300 M115.3,63.6L300,300 M300,300L159.2,35.1 M207.3,14.7L300,300 M258.2,2.9L300,300 M300,300L310.5,0.2 M362.4,6.6L300,300
       M412.4,21.8L300,300 M459,45.6L300,300 M500.7,77.1L99.3,522.9 M63.6,484.7l472.8-369.4 M35.1,440.8l529.8-281.7 M14.7,392.7
      l570.6-185.4 M2.9,341.8l594.2-83.5 M0.7,279.1l598.5,41.9 M8.9,227.4l582.2,145.2 M25.9,178l548.1,244 M51.3,132.2l497.4,335.5
       M84.2,91.6L300,300 M123.7,57.3L300,300 M300,300L168.5,30.4 M217.3,11.6L300,300 M268.6,1.6L300,300 M300,300L320.9,0.7
       M372.6,8.9L300,300 M422,25.9L300,300 M467.8,51.3L300,300 M508.4,84.2L91.6,515.8 M57.3,476.3l485.4-352.7 M30.4,431.5l539.3-263
       M11.6,382.7l576.8-165.4 M1.6,331.4l596.7-62.7 M1.6,268.6l596.7,62.7 M11.6,217.3l576.8,165.4 M30.4,168.5l539.3,263 M57.3,123.7
      l485.4,352.7 M91.6,84.2L300,300 M132.2,51.3L300,300 M300,300L178,25.9 M227.4,8.9L300,300 M279.1,0.7L300,300 M300,300L331.4,1.6
       M382.7,11.6L300,300 M431.5,30.4L300,300 M476.3,57.3L300,300 M515.8,91.6L84.2,508.4 M51.3,467.8l497.4-335.5 M25.9,422
      l548.1-244 M8.9,372.6l582.2-145.2 M0.7,320.9l598.5-41.9 M2.9,258.2l594.2,83.5 M14.7,207.3l570.6,185.4 M35.1,159.2l529.8,281.7
       M63.6,115.3l472.8,369.4 M99.3,77.1L300,300 M141,45.6L300,300 M300,300L187.6,21.8 M237.6,6.6L300,300 M289.5,0.2L300,300
       M300,300L341.8,2.9 M392.7,14.7L300,300 M440.8,35.1L300,300 M484.7,63.6L300,300 M522.9,99.3L77.1,500.7 M45.6,459l508.8-318
       M21.8,412.4l556.3-224.8 M6.6,362.4l586.9-124.7 M0.2,310.5l599.6-20.9"/>

    <path mask="url(#m2)" d="M4.6,247.9l590.9,104.2 M18.1,197.4l563.8,205.2 M40.2,150l519.6,300 M70.2,107.2l459.6,385.7 M107.2,70.2
      L300,300 M150,40.2L300,300 M300,300L197.4,18.1 M247.9,4.6L300,300 M300,0v300 M300,300L352.1,4.6 M402.6,18.1L300,300 M450,40.2
      L300,300 M492.8,70.2L300,300 M529.8,107.2L70.2,492.8 M40.2,450l519.6-300 M18.1,402.6l563.8-205.2 M4.6,352.1l590.9-104.2 M0,300
      l600,0"/>
  </g>
  
  <circle class="st2" cx="300" cy="300" r="118" stroke-width="1.5" opacity="0.7"/>  

  
  <g class="needle" stroke-width="2">
    <circle class="ring2" cx="300" cy="300" r="100" stroke-width="4.5" />  
    <line x1="300" y1="400" x2="300" y2="600" stroke-width="3"/>
  </g>

  <circle class="ring3" cx="300" cy="300" r="300" stroke-width="1.5" />
  
  <circle class="redzone" cx="300" cy="300" r="315" stroke-width="6" stroke="hsl(10,85%,50%)" />
  
  <text class="txt" x="300" y="328" text-anchor="middle" stroke="none" fill="#fff">0</text>
</svg>
</div>

CSS

@import url('https://fonts.googleapis.com/css2?family=Montserrat:wght@300&display=swap');

html, body, .app {
  width:100%;
  height:100%;
  background:#000;
  overflow:hidden;
  font-family: 'Montserrat', sans-serif;
  font-size:85px;
}

canvas, svg {
  position:absolute;
  user-select:none;
}

.app {
  opacity:0;
}

JS

var n = 4,
    dur = 3,
    props = {x:0, y:0, hue:185},
    mph = 0,
    mouseDown = false,
    c = document.getElementById('c'),
    ctx = c.getContext('2d'),
    size, cw, ch,
    img = new Image(),
    ring = new Image(),
    particles = [],
    Particle = function(index){
      this.index = index;
      this.x = this.y = this.progress = this.opacity = this.scale = 1;

      this.draw = function(){
        ctx.translate( cw/2, ch/2 );
        ctx.rotate(this.rot);
        ctx.globalAlpha = this.opacity;
        ctx.globalCompositeOperation = 'overlay'//(this.index%2==0)?'lighter':'overlay';
        ctx.drawImage(img, -size*this.scale/2, -size*this.scale/2, size*this.scale, size*this.scale);
        ctx.rotate(-this.rot);
        ctx.translate( -cw/2, -ch/2 );
      }

      this.tl = gsap.timeline({repeat:-1, repeatRefresh:true})
          .fromTo(this, {
            rot:()=>Math.random()*-0.8,
            scale:()=>3+Math.random(),
          },{
            duration:dur,
            scale:()=>0.5+Math.random(),
            rot:()=>(this.index%2==0)?1:-0.8,
            ease:'none'
          }, 0)
          .fromTo(this, {opacity:0}, {duration:dur/2, opacity:1, yoyo:true, repeat:1, ease:'power1.inOut'}, 0)
          .progress(this.index/n);
    }

ring.src = 'https://assets.codepen.io/721952/speedometerAlpha3.png';
img.src = 'https://assets.codepen.io/721952/grayscaleFlame.jpg';

img.onload = function(){
  updateSize();
  for (var i=0; i<n; i++) particles.push(new Particle(i));
  gsap.ticker.add(redraw);
  gsap.set('.app', {opacity:1});
}

window.onresize = updateSize;
window.onmousedown = window.ontouchstart = (e)=>{ mouseDown=true };
window.onmouseup = window.ontouchend = (e)=>{ mouseDown=false };

window.onmousemove = window.ontouchmove = (e)=>{
  if (e.touches) {
    e.clientX = e.touches[0].clientX;
    e.clientY = e.touches[0].clientY;
  }  
  gsap.to('#c, #s', {
    rotationY:-20+e.clientX/innerWidth*40,
    rotationX:10-e.clientY/innerHeight*20
  });
}

gsap.set('.needle',  { transformOrigin:'100px 100px', rotation:40 });
gsap.set('.ring1',   { transformOrigin:'50% 50%', rotation:130 });
gsap.set('.ring3',   { transformOrigin:'50% 50%', rotation:130, drawSVG:0 });
gsap.set('.redzone', { transformOrigin:'50% 50%', drawSVG:'2.8% 11.2%' });
gsap.set('.app', { perspective:400 });
gsap.set('#s', {overflow:'visible', width:'66.7%', height:'66.7%', left:'50%', top:'50%', xPercent:-50, yPercent:-50, z:20})


function updateSize(){
  cw = (c.width = window.innerWidth);
  ch = (c.height = window.innerHeight);
  size = Math.min(cw/1.5, ch/1.5);
}

function redraw(){ 
  ctx.clearRect(0,0,cw,ch);
  for (var i=0; i<n; i++) particles[i].draw();
  ctx.globalAlpha = 1;
  ctx.globalCompositeOperation = 'multiply';
  ctx.fillStyle = "hsl("+props.hue+", 100%, 50%)";
  ctx.fillRect(cw/2-size/2, ch/2-size/2, size, size); 
  ctx.globalCompositeOperation = 'destination-in';
  ctx.drawImage(ring, cw/2-size/2, ch/2-size/2, size, size);
  
  if (mouseDown && mph<1) {
    mph+=0.0015;
    (mph>0.88 && Math.random()>0.5) ? mph -= 0.002 : mph += 0.0015; // make it quiver at the top end
  }
  else if (mph>0) {
    (mph<0.05) ? mph=0:mph-=0.005;
  }
  
  gsap.to('.txt',     { duration:()=>(mph<0.01)?0.001:0.5, innerHTML:mph*221, snap:{innerHTML:1} })
  gsap.to('.ring3',   { drawSVG:'0 '+mph*75+'%' })
  gsap.to('.ring1',   { drawSVG:mph*75+'% 100%' })  
  gsap.to('.needle',  { rotation:40+mph*270 })
  gsap.set(props,     { hue:()=>(mph<0.9)?185:10 })
}