<script>
  // https://github.com/yiwenl/glsl-fbm/blob/master/3d.glsl
  const fbm = `
  #define NUM_OCTAVES 5

  float mod289(float x){return x - floor(x * (1.0 / 289.0)) * 289.0;}
  vec4 mod289(vec4 x){return x - floor(x * (1.0 / 289.0)) * 289.0;}
  vec4 perm(vec4 x){return mod289(((x * 34.0) + 1.0) * x);}

  float noise(vec3 p){
      vec3 a = floor(p);
      vec3 d = p - a;
      d = d * d * (3.0 - 2.0 * d);

      vec4 b = a.xxyy + vec4(0.0, 1.0, 0.0, 1.0);
      vec4 k1 = perm(b.xyxy);
      vec4 k2 = perm(k1.xyxy + b.zzww);

      vec4 c = k2 + a.zzzz;
      vec4 k3 = perm(c);
      vec4 k4 = perm(c + 1.0);

      vec4 o1 = fract(k3 * (1.0 / 41.0));
      vec4 o2 = fract(k4 * (1.0 / 41.0));

      vec4 o3 = o2 * d.z + o1 * (1.0 - d.z);
      vec2 o4 = o3.yw * d.x + o3.xz * (1.0 - d.x);

      return o4.y * d.y + o4.x * (1.0 - d.y);
  }


  float fbm(vec3 x) {
    float v = 0.0;
    float a = 0.5;
    vec3 shift = vec3(100);
    for (int i = 0; i < NUM_OCTAVES; ++i) {
      v += a * noise(x);
      x = x * 2.0 + shift;
      a *= 0.5;
    }
    return v;
  }
  `;
</script>
<canvas id="cnvsGradient" width="300" height="50" style="position: absolute; margin: 10px; border: 1px solid aqua"/>

body{
  overflow: hidden;
  margin: 0;
}

console.clear();

import * as THREE from "https://cdn.skypack.dev/three@0.136.0";
import { OrbitControls } from "https://cdn.skypack.dev/three@0.136.0/examples/jsm/controls/OrbitControls.js";

let scene = new THREE.Scene();
let camera = new THREE.PerspectiveCamera(60, innerWidth / innerHeight, 1, 100);
camera.position.set(0, 0, 7);
let renderer = new THREE.WebGLRenderer({ antialias: true });
renderer.setSize(innerWidth, innerHeight);
renderer.setClearColor(0xaaaaaa);
document.body.appendChild(renderer.domElement);

let controls = new OrbitControls(camera, renderer.domElement);

let light = new THREE.DirectionalLight(0xffffff);
light.position.setScalar(10);
scene.add(light);
scene.add(new THREE.AmbientLight(0xffffff, 0.5));

let tex = setGradient();

let objs = [
  createMesh(0.5, 0.5, 0.5, -2, 0, 0),
  createMesh(1, 3, 1, 0, 0, 0),
  createMesh(1.5, 2, 1.5, 2, 0, 0)
];

renderer.setAnimationLoop(() => {
  objs.forEach(o => {o.rotation.y += 0.01});
  renderer.render(scene, camera);
});

function createMesh(w, h, d, x, y, z) {
  let g = new THREE.BoxGeometry(w, h, d);

  let uniforms = {
    tex: {
      value: tex
    },
    scaling: {
      value: new THREE.Vector3()
    }
  };
  let m = new THREE.MeshLambertMaterial({
    metalness: 0.25,
    roughness: 0.75,
    onBeforeCompile: (shader) => {
      shader.uniforms.tex = uniforms.tex;
      shader.uniforms.scaling = uniforms.scaling;
      shader.vertexShader = `
      uniform vec3 scaling;
      varying vec3 vPos;
      ${shader.vertexShader}
    `.replace(
        `#include <begin_vertex>`,
        `#include <begin_vertex>
      //vPos = (modelMatrix * vec4(position, 1.0)).xyz;
      vPos = vec3(position * scaling);
      `
      );
      //console.log(shader.vertexShader);
      shader.fragmentShader = `
      uniform sampler2D tex;
      varying vec3 vPos;
      ${fbm}
      ${shader.fragmentShader}      
    `.replace(
        `vec4 diffuseColor = vec4( diffuse, opacity );`,
        `
      float d = fbm(vPos * 0.5);
      for(int i = 0; i < 4; i++){
        d = fbm(vPos * (float(i) + 1.) * d);
      }

      vec3 col = texture(tex, vec2(d, 0.5)).rgb;
      vec4 diffuseColor = vec4( col, opacity );`
      );
      //console.log(shader.fragmentShader);
    }
  });
  let o = new THREE.Mesh(g, m);
  scene.add(o);

  o.updateMatrixWorld();

  let box = new THREE.Box3().setFromObject(o);
  let size = new THREE.Vector3();
  box.getSize(size);

  let scaling = new THREE.Vector3(1, 1, 1);
  let sizeMin = Math.min(size.x, Math.min(size.y, size.z));
  let sizeMax = Math.max(size.x, Math.max(size.y, size.z));
  if (sizeMin < 1) scaling.setScalar(1 / sizeMax);

  uniforms.scaling.value.copy(scaling);
  
  o.position.set(x, y, z);
  
  return o;
}

function setGradient() {
  let canvas = document.getElementById("cnvsGradient");
  let ctx = canvas.getContext("2d");

  let gradient = ctx.createLinearGradient(0, 0, 300, 0);

  gradient.addColorStop(0.15, "#cbff7c");
  gradient.addColorStop(0.5, "#ff007f");
  gradient.addColorStop(0.85, "#0044ff");

  ctx.fillStyle = gradient;
  ctx.fillRect(0, 0, canvas.width, canvas.height);

  return new THREE.CanvasTexture(canvas);
}