glsl-hills.js

/**
 * GLSL animated hills (Three.js) — vanilla port for static pages.
 */
import * as THREE from "three";

const VERTEX_SHADER = `
#define GLSLIFY 1
attribute vec3 position;
uniform mat4 projectionMatrix;
uniform mat4 modelViewMatrix;
uniform float time;
varying vec3 vPosition;

mat4 rotateMatrixX(float radian) {
  return mat4(
    1.0, 0.0, 0.0, 0.0,
    0.0, cos(radian), -sin(radian), 0.0,
    0.0, sin(radian), cos(radian), 0.0,
    0.0, 0.0, 0.0, 1.0
  );
}

vec3 mod289(vec3 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 permute(vec4 x) { return mod289(((x*34.0)+1.0)*x); }
vec4 taylorInvSqrt(vec4 r) { return 1.79284291400159 - 0.85373472095314 * r; }
vec3 fade(vec3 t) { return t*t*t*(t*(t*6.0-15.0)+10.0); }

float cnoise(vec3 P) {
  vec3 Pi0 = floor(P);
  vec3 Pi1 = Pi0 + vec3(1.0);
  Pi0 = mod289(Pi0);
  Pi1 = mod289(Pi1);
  vec3 Pf0 = fract(P);
  vec3 Pf1 = Pf0 - vec3(1.0);
  vec4 ix = vec4(Pi0.x, Pi1.x, Pi0.x, Pi1.x);
  vec4 iy = vec4(Pi0.yy, Pi1.yy);
  vec4 iz0 = Pi0.zzzz;
  vec4 iz1 = Pi1.zzzz;
  vec4 ixy = permute(permute(ix) + iy);
  vec4 ixy0 = permute(ixy + iz0);
  vec4 ixy1 = permute(ixy + iz1);
  vec4 gx0 = ixy0 * (1.0 / 7.0);
  vec4 gy0 = fract(floor(gx0) * (1.0 / 7.0)) - 0.5;
  gx0 = fract(gx0);
  vec4 gz0 = vec4(0.5) - abs(gx0) - abs(gy0);
  vec4 sz0 = step(gz0, vec4(0.0));
  gx0 -= sz0 * (step(0.0, gx0) - 0.5);
  gy0 -= sz0 * (step(0.0, gy0) - 0.5);
  vec4 gx1 = ixy1 * (1.0 / 7.0);
  vec4 gy1 = fract(floor(gx1) * (1.0 / 7.0)) - 0.5;
  gx1 = fract(gx1);
  vec4 gz1 = vec4(0.5) - abs(gx1) - abs(gy1);
  vec4 sz1 = step(gz1, vec4(0.0));
  gx1 -= sz1 * (step(0.0, gx1) - 0.5);
  gy1 -= sz1 * (step(0.0, gy1) - 0.5);
  vec3 g000 = vec3(gx0.x,gy0.x,gz0.x);
  vec3 g100 = vec3(gx0.y,gy0.y,gz0.y);
  vec3 g010 = vec3(gx0.z,gy0.z,gz0.z);
  vec3 g110 = vec3(gx0.w,gy0.w,gz0.w);
  vec3 g001 = vec3(gx1.x,gy1.x,gz1.x);
  vec3 g101 = vec3(gx1.y,gy1.y,gz1.y);
  vec3 g011 = vec3(gx1.z,gy1.z,gz1.z);
  vec3 g111 = vec3(gx1.w,gy1.w,gz1.w);
  vec4 norm0 = taylorInvSqrt(vec4(dot(g000, g000), dot(g010, g010), dot(g100, g100), dot(g110, g110)));
  g000 *= norm0.x; g010 *= norm0.y; g100 *= norm0.z; g110 *= norm0.w;
  vec4 norm1 = taylorInvSqrt(vec4(dot(g001, g001), dot(g011, g011), dot(g101, g101), dot(g111, g111)));
  g001 *= norm1.x; g011 *= norm1.y; g101 *= norm1.z; g111 *= norm1.w;
  float n000 = dot(g000, Pf0);
  float n100 = dot(g100, vec3(Pf1.x, Pf0.yz));
  float n010 = dot(g010, vec3(Pf0.x, Pf1.y, Pf0.z));
  float n110 = dot(g110, vec3(Pf1.xy, Pf0.z));
  float n001 = dot(g001, vec3(Pf0.xy, Pf1.z));
  float n101 = dot(g101, vec3(Pf1.x, Pf0.y, Pf1.z));
  float n011 = dot(g011, vec3(Pf0.x, Pf1.yz));
  float n111 = dot(g111, Pf1);
  vec3 fade_xyz = fade(Pf0);
  vec4 n_z = mix(vec4(n000, n100, n010, n110), vec4(n001, n101, n011, n111), fade_xyz.z);
  vec2 n_yz = mix(n_z.xy, n_z.zw, fade_xyz.y);
  float n_xyz = mix(n_yz.x, n_yz.y, fade_xyz.x);
  return 2.2 * n_xyz;
}

void main(void) {
  vec3 updatePosition = (rotateMatrixX(radians(90.0)) * vec4(position, 1.0)).xyz;
  float sin1 = sin(radians(updatePosition.x / 128.0 * 90.0));
  vec3 noisePosition = updatePosition + vec3(0.0, 0.0, time * -30.0);
  float noise1 = cnoise(noisePosition * 0.08);
  float noise2 = cnoise(noisePosition * 0.06);
  float noise3 = cnoise(noisePosition * 0.4);
  vec3 lastPosition = updatePosition + vec3(0.0,
    noise1 * sin1 * 8.0 + noise2 * sin1 * 8.0 + noise3 * (abs(sin1) * 2.0 + 0.5) + pow(sin1, 2.0) * 40.0, 0.0);
  vPosition = lastPosition;
  gl_Position = projectionMatrix * modelViewMatrix * vec4(lastPosition, 1.0);
}
`;

const FRAGMENT_SHADER = `
precision highp float;
#define GLSLIFY 1
varying vec3 vPosition;

void main(void) {
  float opacity = (96.0 - length(vPosition)) / 256.0 * 0.6;
  vec3 color = vec3(0.6);
  gl_FragColor = vec4(color, opacity);
}
`;

function prefersReducedMotion() {
  return (
    window.matchMedia("(prefers-reduced-motion: reduce)").matches ||
    document.documentElement.getAttribute("data-reduced-motion") === "true"
  );
}

/**
 * @param {HTMLElement} container
 * @param {{ cameraZ?: number, planeSize?: number, speed?: number }} [options]
 * @returns {(() => void) | null}
 */
export function initGLSLHills(container, options = {}) {
  if (!container || prefersReducedMotion()) return null;

  const cameraZ = options.cameraZ ?? 125;
  const planeSize = options.planeSize ?? 256;
  const speed = options.speed ?? 0.5;

  const canvas = document.createElement("canvas");
  canvas.className = "glsl-hills__canvas";
  canvas.setAttribute("aria-hidden", "true");
  container.appendChild(canvas);

  class Plane {
    constructor() {
      this.uniforms = { time: { value: 0 } };
      this.mesh = new THREE.Mesh(
        new THREE.PlaneGeometry(planeSize, planeSize, planeSize, planeSize),
        new THREE.RawShaderMaterial({
          uniforms: this.uniforms,
          vertexShader: VERTEX_SHADER,
          fragmentShader: FRAGMENT_SHADER,
          transparent: true,
        })
      );
      this.time = speed;
    }
    render(delta) {
      this.uniforms.time.value += delta * this.time;
    }
  }

  const renderer = new THREE.WebGLRenderer({ canvas, antialias: false, alpha: true });
  const scene = new THREE.Scene();
  const camera = new THREE.PerspectiveCamera(45, 1, 1, 10000);
  const clock = new THREE.Clock();
  const plane = new Plane();

  const resize = () => {
    const w = container.clientWidth || window.innerWidth;
    const h = container.clientHeight || window.innerHeight;
    canvas.width = w;
    canvas.height = h;
    camera.aspect = w / h;
    camera.updateProjectionMatrix();
    renderer.setSize(w, h, false);
  };

  let animationId = 0;
  const renderLoop = () => {
    plane.render(clock.getDelta());
    renderer.render(scene, camera);
    animationId = requestAnimationFrame(renderLoop);
  };

  renderer.setClearColor(0x000000, 0);
  camera.position.set(0, 16, cameraZ);
  camera.lookAt(new THREE.Vector3(0, 28, 0));
  scene.add(plane.mesh);
  window.addEventListener("resize", resize);
  resize();
  renderLoop();

  return () => {
    cancelAnimationFrame(animationId);
    window.removeEventListener("resize", resize);
    plane.mesh.geometry.dispose();
    plane.mesh.material.dispose();
    renderer.dispose();
    canvas.remove();
  };
}