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Here you can Sed posuere consectetur est at lobortis. Donec ullamcorper nulla non metus auctor fringilla. Maecenas sed diam eget risus varius blandit sit amet non magna. Donec id elit non mi porta gravida at eget metus. Praesent commodo cursus magna, vel scelerisque nisl consectetur et.

HTML

              
                <canvas id="canvas"></canvas>

<h1>What's behind the curtain ?</h1>
<p>This funny interactive curtain is made with ThreeJS, polylines and verlet constraints (adapted from verlet-js).</p>
<p>Feel free to play with conf (<em>nx</em>, <em>gravity</em>...)</p>
              
            
!

CSS

              
                body, html {
  height: 100%;  
}
body {
  margin: 0;
  font-family: 'Montserrat', sans-serif;
  background-image: radial-gradient(circle, #ffffff, #aaaaaa);
}
canvas {
  position: fixed;
  top: 0;
  bottom: 0;
  z-index: 1;
}
h1 {
  font-size: 50px;
  text-align: center;
  width: 60%;
  margin: 0 auto;
  padding-top: 10%;
}
p {
  font-size: 30px;
  text-align: center;
  width: 50%;
  margin: 1em auto 0;
}

              
            
!

JS

              
                function App() {
  const conf = {
    el: 'canvas',
    gravity: -0.2,
    nx: 100,
    ny: 40,
    size: 1.5,
    stiffness: 5,
    mouseRadius: 10,
    mouseStrength: 0.4
  };

  let renderer, scene, camera;
  let width, height;
  const { randFloat: rnd, randFloatSpread: rndFS } = THREE.Math;

  const mouse = new THREE.Vector2(), oldMouse = new THREE.Vector2();
  const verlet = new VerletJS(), polylines = [];
  const uCx = { value: 0 }, uCy = { value: 0 };

  init();

  function init() {
    renderer = new THREE.WebGLRenderer({ canvas: document.getElementById(conf.el), antialias: true, alpha: true });
    camera = new THREE.PerspectiveCamera();

    verlet.width = 256;
    verlet.height = 256;

    updateSize();
    window.addEventListener('resize', updateSize, false);

    initScene();
    initListeners();
    animate();
  }

  function initScene() {
    scene = new THREE.Scene();
    verlet.gravity = new Vec2(0, conf.gravity);
    
    const loader = new THREE.TextureLoader();
    // loader.load('https://klevron.github.io/codepen/misc/curtain.jpg', texture => {
    //   initCurtain(texture);
    // })
    initCurtain();
  }

  function initCurtain() {
    const material = new THREE.ShaderMaterial({
      transparent: true,
      uniforms: {
        uCx, uCy,
        // tDiffuse: { value: texture },
        uSize: { value: conf.size / conf.nx }
      },
      vertexShader: `
        uniform float uCx;
        uniform float uCy;
        uniform float uSize;
        attribute vec3 color;
        attribute vec3 next;
        attribute vec3 prev;
        attribute float side;

        varying vec2 vUv;
        varying vec4 vColor;

        void main() {
          vUv = uv;
          vColor = vec4(color, 0.5 + smoothstep(0.0, 0.5, uv.y) * 0.5);

          vec3 pos = vec3(position.x * uCx, position.y * uCy, 0.0);
          vec2 sprev = vec2(prev.x * uCx, prev.y * uCy);
          vec2 snext = vec2(next.x * uCx, next.y * uCy);

          vec2 tangent = normalize(snext - sprev);
          vec2 normal = vec2(-tangent.y, tangent.x);

          float dist = length(snext - sprev);
          normal *= smoothstep(0.0, 0.02, dist);

          normal *= uSize;// * (1.0 - uv.y);
          pos.xy -= normal * side;

          gl_Position = vec4(pos, 1.0);
        }
      `,
      fragmentShader: `
        // uniform sampler2D tDiffuse;
        varying vec2 vUv;
        varying vec4 vColor;
        void main() {
          // vec4 tex = texture2D(tDiffuse, vUv);
          // tex.a = 0.95;
          // gl_FragColor = tex;
          gl_FragColor = vColor;
        }
      `
    });

    const dx = verlet.width / conf.nx, dy = -verlet.height / (conf.ny - 1);
    const ox = -dx * (conf.nx / 2 - 0.5), oy = verlet.height / 2 - dy / 2;
    // const cscale = chroma.scale([chroma.random(), chroma.random()]);
    // const cscale = chroma.scale([0x09256f, 0x6efec8]);
    const cscale = chroma.scale([0x051924, 0xc00a1c]);
    for (let i = 0; i < conf.nx; i++) {
      const points = [];
      const vpoints = [];
      for (let j = 0; j < conf.ny; j++) {
        const x = ox + i * dx, y = oy + j * dy;
        points.push(new THREE.Vector3(x, y, 0));
        vpoints.push(new Vec2(x, y));
      }
      const polyline = new Polyline({ points, color1: cscale(rnd(0, 1)), color2: cscale(rnd(0, 1)), uvx: (i + 1) / conf.nx, uvdx: conf.size / conf.nx });
      polylines.push(polyline);

      polyline.segment = verlet.lineSegments(vpoints, conf.stiffness);
      polyline.segment.pin(0);
      // polyline.segment.particles.forEach(p => { p.pos.x += rndFS(5); });

      const mesh = new THREE.Mesh(polyline.geometry, material);
      scene.add(mesh);
    }

    for (let i = 0; i < verlet.width; i++) {
      const ox = -verlet.width / 2;
      setTimeout(() => {
        _move(new THREE.Vector2(ox + i, 0), new THREE.Vector2(ox + i + 1, 0));
      }, i * 15);
    }
  }

  function updatePoints() {
    polylines.forEach(line => {
      for (let i = 0; i < line.points.length; i++) {
        const p = line.segment.particles[i].pos;
        line.points[i].x = p.x;
        line.points[i].y = p.y;
      }
      line.updateGeometry();
    });
  }

  function updateColors() {
    const c1 = chroma.random(), c2 = chroma.random();
    const cscale = chroma.scale([c1, c2]);
    console.log(c1.hex(), c2.hex());
    // #21a25f #a0fa42
    // #09256f #6efec8
    polylines.forEach(line => {
      line.color1 = cscale(rnd(0, 1));
      line.color2 = cscale(rnd(0, 1));
      const cscale1 = chroma.scale([line.color1, line.color2]);
      const colors = line.geometry.attributes.color.array;
      const c = new THREE.Color();
      for (let i = 0; i < line.count; i++) {
        c.set(cscale1(i / line.count).hex());
        c.toArray(colors, (i * 2) * 3);
        c.toArray(colors, (i * 2 + 1) * 3);
      }
      line.geometry.attributes.color.needsUpdate = true;
    });
  }

  function animate() {
    verlet.frame(16);
    updatePoints();
    renderer.render(scene, camera);
    requestAnimationFrame(animate);
  }

  function initListeners() {
    if ('ontouchstart' in window) {
      document.body.addEventListener('touchstart', updateMouse, false);
      document.body.addEventListener('touchmove', move, false);
    } else {
      document.body.addEventListener('mouseenter', updateMouse, false);
      document.body.addEventListener('mousemove', move, false);
    }
    document.body.addEventListener('click', updateColors, false);
  }

  function move(e) {
    updateMouse(e);
    _move(oldMouse, mouse);
  }

  function _move(oV, nV) {
    const v1 = new THREE.Vector2(), v2 = new THREE.Vector2();
    polylines.forEach(line => {
      for (let i = 0; i < line.points.length; i++) {
        const p = line.segment.particles[i].pos;
        const l = v1.copy(oV).sub(v2.set(p.x, p.y)).length();
        if (l < conf.mouseRadius) {
          v1.copy(nV).sub(oV).multiplyScalar(conf.mouseStrength);
          p.x += v1.x; p.y += v1.y;
        }
      }
    });
  }

  function updateMouse(e) {
    if (e.changedTouches && e.changedTouches.length) {
      e.x = e.changedTouches[0].pageX;
      e.y = e.changedTouches[0].pageY;
    }
    if (e.x === undefined) {
      e.x = e.pageX;
      e.y = e.pageY;
    }

    oldMouse.copy(mouse);
    mouse.set(
      (e.x - width / 2) * verlet.width / width,
      (height / 2 - e.y) * verlet.height / height
    );
  }

  function updateSize() {
    width = window.innerWidth;
    height = window.innerHeight;
    uCx.value = 2 / verlet.width; uCy.value = 2 / verlet.height;
    renderer.setSize(width, height);
    // camera.aspect = width / height;
    // camera.updateProjectionMatrix();
  }
}

// adapted from https://github.com/oframe/ogl/blob/master/src/extras/Polyline.js
const Polyline = (function () {
  const tmp = new THREE.Vector3();

  class Polyline {
    constructor(params) {
      const { points, color1, color2, uvx, uvdx } = params;
      this.points = points;
      this.count = points.length;
      this.color1 = color1; this.color2 = color2;
      this.uvx = uvx; this.uvdx = uvdx;
      this.init();
      this.updateGeometry();
    }

    init() {
      // const cscale = chroma.scale([chroma.random(), chroma.random()]);
      const cscale = chroma.scale([this.color1, this.color2]);
      this.geometry = new THREE.BufferGeometry();
      this.position = new Float32Array(this.count * 3 * 2);
      this.prev = new Float32Array(this.count * 3 * 2);
      this.next = new Float32Array(this.count * 3 * 2);
      const side = new Float32Array(this.count * 1 * 2);
      const uv = new Float32Array(this.count * 2 * 2);
      const color = new Float32Array(this.count * 3 * 2);
      const index = new Uint16Array((this.count - 1) * 3 * 2);

      const c = new THREE.Color();
      for (let i = 0; i < this.count; i++) {
        const i2 = i * 2;
        side.set([-1, 1], i2);
        const v = 1 - i / (this.count - 1);
        // uv.set([0, v, 1, v], i * 4);
        uv.set([this.uvx, v, this.uvx - this.uvdx, v], i * 4);

        c.set(cscale(v).hex());
        c.toArray(color, i2 * 3);
        c.toArray(color, (i2 + 1) * 3);

        if (i === this.count - 1) continue;
        index.set([i2 + 0, i2 + 1, i2 + 2], (i2 + 0) * 3);
        index.set([i2 + 2, i2 + 1, i2 + 3], (i2 + 1) * 3);
      }

      this.geometry.setAttribute('position', new THREE.BufferAttribute(this.position, 3));
      this.geometry.setAttribute('color', new THREE.BufferAttribute(color, 3));
      this.geometry.setAttribute('prev', new THREE.BufferAttribute(this.prev, 3));
      this.geometry.setAttribute('next', new THREE.BufferAttribute(this.next, 3));
      this.geometry.setAttribute('side', new THREE.BufferAttribute(side, 1));
      this.geometry.setAttribute('uv', new THREE.BufferAttribute(uv, 2));
      this.geometry.setIndex(new THREE.BufferAttribute(index, 1));
    }

    updateGeometry() {
      this.points.forEach((p, i) => {
        p.toArray(this.position, i * 3 * 2);
        p.toArray(this.position, i * 3 * 2 + 3);

        if (!i) {
          tmp.copy(p).sub(this.points[i + 1]).add(p);
          tmp.toArray(this.prev, i * 3 * 2);
          tmp.toArray(this.prev, i * 3 * 2 + 3);
        } else {
          p.toArray(this.next, (i - 1) * 3 * 2);
          p.toArray(this.next, (i - 1) * 3 * 2 + 3);
        }

        if (i === this.points.length - 1) {
          tmp.copy(p).sub(this.points[i - 1]).add(p);
          tmp.toArray(this.next, i * 3 * 2);
          tmp.toArray(this.next, i * 3 * 2 + 3);
        } else {
          p.toArray(this.prev, (i + 1) * 3 * 2);
          p.toArray(this.prev, (i + 1) * 3 * 2 + 3);
        }
      });

      this.geometry.attributes.position.needsUpdate = true;
      this.geometry.attributes.prev.needsUpdate = true;
      this.geometry.attributes.next.needsUpdate = true;
    }
  }

  return Polyline;
})();

App();

              
            
!
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