<section class="section section--1">
  <canvas class="section__canv" data-src="https://images.unsplash.com/photo-1574158622682-e40e69881006?ixlib=rb-1.2.1&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=512&h=512&q=80"></canvas>
</section>
<section class="section section--2">
  <canvas class="section__canv" data-src="https://images.unsplash.com/photo-1592194996308-7b43878e84a6?ixlib=rb-1.2.1&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=512&h=512&q=80"></canvas>
</section>
<section class="section section--3">
  <canvas class="section__canv" data-src="https://images.unsplash.com/photo-1536590158209-e9d615d525e4?ixlib=rb-1.2.1&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=512&h=512&q=80"></canvas>
</section>
<section class="section section--4">
  <canvas class="section__canv" data-src="https://images.unsplash.com/photo-1518791841217-8f162f1e1131?ixlib=rb-1.2.1&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=512&h=512&q=80"></canvas>
</section>
<section class="section section--5">
  <canvas class="section__canv" data-src="https://images.unsplash.com/photo-1533738363-b7f9aef128ce?ixlib=rb-1.2.1&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=512&h=512&q=80"></canvas>
</section>

body {
  margin: 0;
}

.section {
  min-height: 75vh;
  display: grid;
  place-content: center;
  background-color: #bbb;
}

.section--1 {
  margin-top: 50vh;
}

.section--5 {
  margin-bottom: 30vh;
}

.section:nth-child(even) {
  background-color: #ddd;
}

.section__canv {
  display: block;
}

import {
  Renderer,
  Triangle,
  Program,
  TextureLoader,
  Transform,
  Mesh,
  Vec2,
  Vec3
} from "https://cdn.skypack.dev/ogl@0.0.76";

import ScrollMagic from "https://cdn.skypack.dev/scrollmagic@2.0.8";
import "https://cdn.skypack.dev/scrollmagic@2.0.8/scrollmagic/uncompressed/plugins/debug.addIndicators";

const vertex = /* glsl */ `
attribute vec2 uv;
attribute vec2 position;
varying vec2 vUv;
void main() {
  vUv = uv;
  gl_Position = vec4(position, 0, 1);
}`;

const fragment = /* glsl */ `
precision highp float;
uniform float uProgress;
uniform sampler2D tMap;
uniform vec3 uResolution;

varying vec2 vUv;

// Simplex 2D noise
//
vec3 permute(vec3 x) { return mod(((x*34.0)+1.0)*x, 289.0); }

float snoise(vec2 v){
  const vec4 C = vec4(0.211324865405187, 0.366025403784439,
           -0.577350269189626, 0.024390243902439);
  vec2 i  = floor(v + dot(v, C.yy) );
  vec2 x0 = v -   i + dot(i, C.xx);
  vec2 i1;
  i1 = (x0.x > x0.y) ? vec2(1.0, 0.0) : vec2(0.0, 1.0);
  vec4 x12 = x0.xyxy + C.xxzz;
  x12.xy -= i1;
  i = mod(i, 289.0);
  vec3 p = permute( permute( i.y + vec3(0.0, i1.y, 1.0 ))
  + i.x + vec3(0.0, i1.x, 1.0 ));
  vec3 m = max(0.5 - vec3(dot(x0,x0), dot(x12.xy,x12.xy),
    dot(x12.zw,x12.zw)), 0.0);
  m = m*m ;
  m = m*m ;
  vec3 x = 2.0 * fract(p * C.www) - 1.0;
  vec3 h = abs(x) - 0.5;
  vec3 ox = floor(x + 0.5);
  vec3 a0 = x - ox;
  m *= 1.79284291400159 - 0.85373472095314 * ( a0*a0 + h*h );
  vec3 g;
  g.x  = a0.x  * x0.x  + h.x  * x0.y;
  g.yz = a0.yz * x12.xz + h.yz * x12.yw;
  return 130.0 * dot(m, g);
}

vec2 cover(vec2 res, vec2 uv, vec2 pivot) {
  vec2 ratio = vec2(max(res.x, res.y)) / res;
  return (uv - pivot) / ratio + pivot;
}

void main() {
  vec2 uv = cover(uResolution.xy, vUv, vec2(0.5));
  float noize = snoise(uv * 6.0) * 0.5 + 0.5;
  noize = smoothstep(uProgress - 0.05, uProgress + 0.05, mix(0.05, 0.95, noize));
  
  vec4 tex = texture2D(tMap, uv);
  gl_FragColor.rgb = tex.rgb;
  gl_FragColor.a = 1.0 - noize;
}`;

function onSectionScroll(progress, renderer, scene, mesh) {
  mesh.program.uniforms.uProgress.value = progress;
  renderer.render({ scene });
}

const controller = new ScrollMagic.Controller({ addIndicators: true });

document.querySelectorAll(".section").forEach((section) => {
  const canvas = section.querySelector(".section__canv");
  
  const imageSrc = canvas.dataset.src;
  if (!imageSrc) return;
  
  const renderer = new Renderer({ canvas, antialias: true, alpha: true });
  renderer.setSize(300, 200);
  const gl = renderer.gl;
  gl.clearColor(0, 0, 0, 0);
  
  const scene = new Transform();
  const geometry = new Triangle(gl);
  const texture = TextureLoader.load(gl, { src: { jpg: imageSrc }});
  
  const program = new Program(gl, {
    vertex,
    fragment,
    uniforms: {
      uProgress: { value: 0 },
      uResolution: { value: new Vec3(300, 200, 1) },
      tMap: { value: texture },
    },
  });
  
  const mesh = new Mesh(gl, { geometry, program });
  mesh.setParent(scene);
  
  texture.loaded.then(() => renderer.render({ scene }));
  
  new ScrollMagic.Scene({
    triggerElement: section,
    duration: () => section.offsetHeight * 1
  })
    .on("progress", ({ progress }) => onSectionScroll(progress, renderer, scene, mesh))
    //.trigger("progress")
    .addTo(controller);
});