particles/chua-attractor.html at main · danlex/particles · GitHub

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<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Chua Attractor — Particles</title>
  <meta name="description" content="Leon Chua's famous chaotic circuit. A double-scroll shape from a piecewise-linear nonlinearity.">
  <meta name="author" content="Alexandru DAN">
  <meta name="theme-color" content="#050505">
  <link rel="canonical" href="https://particles.alexandrudan.com/chua-attractor.html">
  <link rel="icon" type="image/svg+xml" href="favicon.svg">

  <!-- Open Graph -->
  <meta property="og:type" content="website">
  <meta property="og:url" content="https://particles.alexandrudan.com/chua-attractor.html">
  <meta property="og:title" content="Chua Attractor — Particles">
  <meta property="og:description" content="Leon Chua's famous chaotic circuit. A double-scroll shape from a piecewise-linear nonlinearity.">
  <meta property="og:image" content="https://particles.alexandrudan.com/og-image.svg">
  <meta property="og:site_name" content="Particles">

  <!-- Twitter -->
  <meta name="twitter:card" content="summary_large_image">
  <meta name="twitter:title" content="Chua Attractor — Particles">
  <meta name="twitter:description" content="Leon Chua's famous chaotic circuit. A double-scroll shape from a piecewise-linear nonlinearity.">
  <meta name="twitter:image" content="https://particles.alexandrudan.com/og-image.svg">
  <style>
    * { margin: 0; padding: 0; box-sizing: border-box; }
    body { background: #000; overflow: hidden; font-family: 'Courier New', monospace; }
    canvas { display: block; }
    #controls {
      position: fixed;
      bottom: 24px;
      left: 50%;
      transform: translateX(-50%);
      display: flex;
      gap: 20px;
      background: rgba(0,0,0,0.6);
      backdrop-filter: blur(12px);
      border: 1px solid rgba(255,255,255,0.08);
      border-radius: 12px;
      padding: 14px 28px;
      z-index: 10;
      align-items: center;
    }
    .ctrl-group {
      display: flex; flex-direction: column; align-items: center; gap: 4px;
    }
    .ctrl-group label {
      color: rgba(255,255,255,0.4); font-size: 9px;
      text-transform: uppercase; letter-spacing: 1.5px;
    }
    .ctrl-group input[type="range"] {
      -webkit-appearance: none; width: 100px; height: 3px;
      background: rgba(255,255,255,0.15); border-radius: 2px; outline: none;
    }
    .ctrl-group input[type="range"]::-webkit-slider-thumb {
      -webkit-appearance: none; width: 12px; height: 12px;
      border-radius: 50%; background: #fff; cursor: pointer;
    }
    #info {
      position: fixed; top: 24px; left: 28px; z-index: 10;
    }
    #info h1 {
      color: rgba(255,255,255,0.7); font-size: 14px; font-weight: 400;
      letter-spacing: 3px; text-transform: uppercase;
    }
    #info p {
      color: rgba(255,255,255,0.25); font-size: 10px;
      margin-top: 6px; letter-spacing: 1px;
    }
    #fps {
      position: fixed; top: 24px; right: 28px;
      color: rgba(255,255,255,0.2); font-size: 10px;
      letter-spacing: 1px; z-index: 10;
    }
    #back {
      position: fixed; top: 24px; left: 50%; transform: translateX(-50%);
      z-index: 10;
    }
    #back a {
      color: rgba(255,255,255,0.2); font-size: 9px; text-decoration: none;
      letter-spacing: 2px; text-transform: uppercase;
      transition: color 0.3s;
    }
    #back a:hover { color: rgba(255,255,255,0.5); }
      .zoom-btn {
      width: 32px; height: 32px; border-radius: 50%;
      background: rgba(255,255,255,0.06); border: 1px solid rgba(255,255,255,0.12);
      color: rgba(255,255,255,0.5); font-size: 18px; cursor: pointer;
      display: flex; align-items: center; justify-content: center;
      transition: background 0.2s;
      font-family: monospace;
    }
    .zoom-btn:hover { background: rgba(255,255,255,0.12); }
  </style>
</head>
<body>
  <div id="info">
    <h1>Chua Attractor</h1>
    <p id="particle-count"></p>
  </div>
  <div id="fps"></div>
  <div id="back"><a href="index.html">Gallery</a></div>
  <div id="controls">
    <div class="ctrl-group">
      <input type="range" id="speed" min="0.1" max="5" step="0.1" value="1">
      <label>Speed</label>
    </div>
    <div class="ctrl-group">
      <input type="range" id="bloom" min="0" max="3" step="0.1" value="0.4">
      <label>Bloom</label>
    </div>
    <div class="ctrl-group">
      <input type="range" id="size" min="0.5" max="4" step="0.1" value="1.0">
      <label>Size</label>
    </div>
    <div class="ctrl-group">
      <input type="range" id="hueShift" min="0" max="1" step="0.01" value="0">
      <label>Hue</label>
    </div>
    <button class="zoom-btn" id="zoomOut">−</button>
    <button class="zoom-btn" id="zoomIn">+</button>
  </div>

  <script type="importmap">
  {
    "imports": {
      "three": "https://cdn.jsdelivr.net/npm/three@0.160.0/build/three.module.js",
      "three/addons/": "https://cdn.jsdelivr.net/npm/three@0.160.0/examples/jsm/"
    }
  }
  </script>
  <script type="module">
    import * as THREE from 'three';
    import { OrbitControls } from 'three/addons/controls/OrbitControls.js';
    import { EffectComposer } from 'three/addons/postprocessing/EffectComposer.js';
    import { RenderPass } from 'three/addons/postprocessing/RenderPass.js';
    import { UnrealBloomPass } from 'three/addons/postprocessing/UnrealBloomPass.js';
    import { GPUComputationRenderer } from 'three/addons/misc/GPUComputationRenderer.js';

    const WIDTH = 256;
    const PARTICLE_COUNT = WIDTH * WIDTH;

    // Scene
    const scene = new THREE.Scene();
    const camera = new THREE.PerspectiveCamera(60, innerWidth / innerHeight, 0.1, 2000);
    camera.position.set(0, 3, 28);

    const renderer = new THREE.WebGLRenderer({ antialias: false, powerPreference: 'high-performance' });
    renderer.setSize(innerWidth, innerHeight);
    renderer.setPixelRatio(1);
    document.body.appendChild(renderer.domElement);

    const orbitControls = new OrbitControls(camera, renderer.domElement);
    orbitControls.enableDamping = true;
    orbitControls.dampingFactor = 0.05;
    orbitControls.autoRotate = true;
    orbitControls.autoRotateSpeed = 0.5;

    // Post-processing
    const composer = new EffectComposer(renderer);
    composer.addPass(new RenderPass(scene, camera));
    const bloomPass = new UnrealBloomPass(
      new THREE.Vector2(innerWidth / 2, innerHeight / 2),
      0.4, 0.3, 0.85
    );
    composer.addPass(bloomPass);

    // GPU Computation
    const gpuCompute = new GPUComputationRenderer(WIDTH, WIDTH, renderer);
    const posTex0 = gpuCompute.createTexture();

    function seedTexture(tex) {
      const data = tex.image.data;
      const ALPHA = 15.6, BETA = 28.0, M0 = -1.143, M1 = -0.714, DT = 0.005;
      const NUM_TRAILS = 64;
      const PER_TRAIL = Math.floor(PARTICLE_COUNT / NUM_TRAILS);

      function chuaF(x) {
        return M1 * x + 0.5 * (M0 - M1) * (Math.abs(x + 1) - Math.abs(x - 1));
      }

      for (let trail = 0; trail < NUM_TRAILS; trail++) {
        let x = 0.7 + trail * 0.02 * Math.sin(trail * 0.9);
        let y = 0.0 + trail * 0.015 * Math.cos(trail * 1.2);
        let z = 0.0 + trail * 0.02 * Math.sin(trail * 0.6);

        for (let j = 0; j < PER_TRAIL; j++) {
          const i = trail * PER_TRAIL + j;
          if (i >= PARTICLE_COUNT) break;

          const steps = 3 + Math.floor(j * 0.2);
          for (let s = 0; s < steps; s++) {
            const dx1 = ALPHA * (y - x - chuaF(x));
            const dy1 = x - y + z;
            const dz1 = -BETA * y;
            const x2 = x+dx1*DT*0.5, y2 = y+dy1*DT*0.5, z2 = z+dz1*DT*0.5;
            const dx2 = ALPHA * (y2 - x2 - chuaF(x2));
            const dy2 = x2 - y2 + z2;
            const dz2 = -BETA * y2;
            const x3 = x+dx2*DT*0.5, y3 = y+dy2*DT*0.5, z3 = z+dz2*DT*0.5;
            const dx3 = ALPHA * (y3 - x3 - chuaF(x3));
            const dy3 = x3 - y3 + z3;
            const dz3 = -BETA * y3;
            const x4 = x+dx3*DT, y4 = y+dy3*DT, z4 = z+dz3*DT;
            const dx4 = ALPHA * (y4 - x4 - chuaF(x4));
            const dy4 = x4 - y4 + z4;
            const dz4 = -BETA * y4;
            x += (dx1+2*dx2+2*dx3+dx4)*DT/6;
            y += (dy1+2*dy2+2*dy3+dy4)*DT/6;
            z += (dz1+2*dz2+2*dz3+dz4)*DT/6;
          }

          const idx = i * 4;
          data[idx]     = x;
          data[idx + 1] = y;
          data[idx + 2] = z;
          data[idx + 3] = 0;
        }
      }
    }

    seedTexture(posTex0);

    const positionShader = `
      uniform vec3 uMouse;
      uniform float uMouseActive;
      uniform float uDt;
      uniform float uSpeed;
      uniform float uFrame;

      float hash(vec2 p) {
        vec3 p3 = fract(vec3(p.xyx) * 0.1031);
        p3 += dot(p3, p3.yzx + 33.33);
        return fract((p3.x + p3.y) * p3.z);
      }

      float noise(vec2 p) {
        return hash(p) * 2.0 - 1.0;
      }

      float chuaF(float x) {
        float m0 = -1.143;
        float m1 = -0.714;
        return m1 * x + 0.5 * (m0 - m1) * (abs(x + 1.0) - abs(x - 1.0));
      }

      void main() {
        vec2 uv = gl_FragCoord.xy / resolution.xy;
        vec4 pos = texture2D(texturePosition, uv);

        float x = pos.x;
        float y = pos.y;
        float z = pos.z;

        float alpha = 15.6;
        float beta = 28.0;

        float dt = uDt * uSpeed;

        // RK2 midpoint method
        float dx1 = alpha * (y - x - chuaF(x));
        float dy1 = x - y + z;
        float dz1 = -beta * y;

        float mx = x + dx1 * dt * 0.5;
        float my = y + dy1 * dt * 0.5;
        float mz = z + dz1 * dt * 0.5;

        float dx2 = alpha * (my - mx - chuaF(mx));
        float dy2 = mx - my + mz;
        float dz2 = -beta * my;

        vec2 seed = uv * 1000.0 + uFrame;
        float nx = noise(seed) * 0.015;
        float ny = noise(seed + 100.0) * 0.015;
        float nz = noise(seed + 200.0) * 0.015;

        x += dx2 * dt + nx;
        y += dy2 * dt + ny;
        z += dz2 * dt + nz;

        float speed = length(vec3(dx1, dy1, dz1));

        // Mouse attraction
        if (uMouseActive > 0.01) {
          vec3 toMouse = uMouse - vec3(x, y, z);
          float mouseDist = length(toMouse);
          float mouseForce = uMouseActive * 0.3 / (mouseDist * mouseDist + 1.0);
          x += toMouse.x * mouseForce * dt;
          y += toMouse.y * mouseForce * dt;
          z += toMouse.z * mouseForce * dt;
        }


        gl_FragColor = vec4(x, y, z, speed);
      }
    `;

    const posVar = gpuCompute.addVariable('texturePosition', positionShader, posTex0);
    gpuCompute.setVariableDependencies(posVar, [posVar]);

    posVar.material.uniforms.uDt = { value: 0.005 };
    posVar.material.uniforms.uSpeed = { value: 1.0 };
    posVar.material.uniforms.uFrame = { value: 0.0 };
    posVar.material.uniforms.uMouse = { value: new THREE.Vector3(0, 0, -1000) };
    posVar.material.uniforms.uMouseActive = { value: 0.0 };

    posVar.wrapS = THREE.RepeatWrapping;
    posVar.wrapT = THREE.RepeatWrapping;

    const err = gpuCompute.init();
    if (err !== null) console.error('GPU Computation init error:', err);

    // Particle Rendering
    const vertexShader = `
      uniform sampler2D uPositionTexture;
      uniform float uHueShift;
      uniform float uPointSize;
      uniform float uScale;
      attribute vec2 aTexCoord;
      varying vec3 vColor;

      vec3 hsl2rgb(float h, float s, float l) {
        float c = (1.0 - abs(2.0 * l - 1.0)) * s;
        float h6 = h * 6.0;
        float x = c * (1.0 - abs(mod(h6, 2.0) - 1.0));
        float m = l - c * 0.5;
        vec3 rgb;
        if (h6 < 1.0) rgb = vec3(c, x, 0.0);
        else if (h6 < 2.0) rgb = vec3(x, c, 0.0);
        else if (h6 < 3.0) rgb = vec3(0.0, c, x);
        else if (h6 < 4.0) rgb = vec3(0.0, x, c);
        else if (h6 < 5.0) rgb = vec3(x, 0.0, c);
        else rgb = vec3(c, 0.0, x);
        return rgb + m;
      }

      void main() {
        vec4 posData = texture2D(uPositionTexture, aTexCoord);
        float x = posData.x;
        float y = posData.y;
        float z = posData.z;
        float speed = posData.w;

        vec3 pos = vec3(x, y, z) * uScale;

        // Color: scroll side (sign of x) -> hue, speed -> brightness
        float scrollSide = step(0.0, x);
        float hue = fract(scrollSide * 0.5 + 0.08 + uHueShift);
        float saturation = 0.85;
        float lightness = 0.12 + min(speed / 4.0, 0.25);

        vColor = hsl2rgb(hue, saturation, lightness);

        vec4 mvPosition = modelViewMatrix * vec4(pos, 1.0);
        gl_PointSize = uPointSize * (55.0 / -mvPosition.z);
        gl_PointSize = max(gl_PointSize, 0.3);
        gl_Position = projectionMatrix * mvPosition;
      }
    `;

    const fragmentShader = `
      varying vec3 vColor;
      void main() {
        float d = length(gl_PointCoord - 0.5) * 2.0;
        if (d > 1.0) discard;
        // Soft gaussian falloff with bright core
        float glow = exp(-d * d * 3.0);
        float core = exp(-d * d * 12.0);
        float alpha = (glow * 0.15 + core * 0.3);
        // Slight color boost at core (hotter center)
        vec3 col = vColor + core * 0.15;
        gl_FragColor = vec4(col, alpha);
      }
    `;

    const geometry = new THREE.BufferGeometry();
    const texCoords = new Float32Array(PARTICLE_COUNT * 2);
    for (let j = 0; j < WIDTH; j++) {
      for (let i = 0; i < WIDTH; i++) {
        const idx = (j * WIDTH + i) * 2;
        texCoords[idx]     = (i + 0.5) / WIDTH;
        texCoords[idx + 1] = (j + 0.5) / WIDTH;
      }
    }
    const dummyPositions = new Float32Array(PARTICLE_COUNT * 3);
    geometry.setAttribute('position', new THREE.BufferAttribute(dummyPositions, 3));
    geometry.setAttribute('aTexCoord', new THREE.BufferAttribute(texCoords, 2));

    const material = new THREE.ShaderMaterial({
      vertexShader,
      fragmentShader,
      uniforms: {
        uPositionTexture: { value: null },
        uHueShift: { value: 0.0 },
        uPointSize: { value: 1.5 },
        uScale: { value: 4.2 },
      },
      transparent: true,
      blending: THREE.AdditiveBlending,
      depthWrite: false,
    });

    const points = new THREE.Points(geometry, material);
    const pivot = new THREE.Group(); pivot.add(points); scene.add(pivot);

    // UI
    document.getElementById('particle-count').textContent =
      `${PARTICLE_COUNT.toLocaleString()} particles — fully GPU computed`;

    const speedSlider = document.getElementById('speed');
    const bloomSlider = document.getElementById('bloom');
    const sizeSlider = document.getElementById('size');
    const hueSlider = document.getElementById('hueShift');
    const fpsEl = document.getElementById('fps');

    document.getElementById('zoomIn').addEventListener('click', () => {
      material.uniforms.uScale.value *= 1.15;
    });
    document.getElementById('zoomOut').addEventListener('click', () => {
      material.uniforms.uScale.value *= 0.85;
    });

    // Animation Loop
    // Mouse interaction
    const mouse = new THREE.Vector2();
    const mouse3D = new THREE.Vector3();
    const raycaster = new THREE.Raycaster();
    let mouseActive = false;

    renderer.domElement.addEventListener('mousemove', (e) => {
      mouse.x = (e.clientX / innerWidth) * 2 - 1;
      mouse.y = -(e.clientY / innerHeight) * 2 + 1;
      mouseActive = true;
      raycaster.setFromCamera(mouse, camera);
      mouse3D.copy(raycaster.ray.direction).multiplyScalar(15).add(camera.position);
    });
    renderer.domElement.addEventListener('mouseleave', () => { mouseActive = false; });

    let lastTime = performance.now();
    let frameCount = 0;

    function animate(now) {
      requestAnimationFrame(animate);

      frameCount++;
      if (now - lastTime >= 1000) {
        fpsEl.textContent = `${frameCount} FPS`;
        frameCount = 0;
        lastTime = now;
      }

      posVar.material.uniforms.uSpeed.value = parseFloat(speedSlider.value);
      posVar.material.uniforms.uFrame.value += 1.0;
      bloomPass.strength = parseFloat(bloomSlider.value);
      material.uniforms.uHueShift.value = parseFloat(hueSlider.value);
      material.uniforms.uPointSize.value = parseFloat(sizeSlider.value);

      // Update mouse uniforms
      if (mouseActive) {
        posVar.material.uniforms.uMouse.value.copy(mouse3D);
        posVar.material.uniforms.uMouseActive.value = 1.0;
      } else {
        posVar.material.uniforms.uMouseActive.value *= 0.95;
      }


      gpuCompute.compute();

      material.uniforms.uPositionTexture.value =
        gpuCompute.getCurrentRenderTarget(posVar).texture;

      pivot.rotation.x += 0.0008;
      orbitControls.update();
      composer.render();
    }

    animate(performance.now());

    // Resize
    window.addEventListener('resize', () => {
      camera.aspect = innerWidth / innerHeight;
      camera.updateProjectionMatrix();
      renderer.setSize(innerWidth, innerHeight);
      composer.setSize(innerWidth, innerHeight);
    });
  </script>
<script src="shared-ui.js"></script>
</body>
</html>