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golden-splash

A JS snippet on QuikRun, callable at quik.run/r/golden-splash.

JS· node:20· 5 runs· 0 forks· updated 1h ago
Endpointquik.run/r/golden-splashRunFork
golden-splash.js
// golden-splash — a WebGL fluid-simulation cursor: move and paint swirling
// golden ink (ported from React Bits SplashCursor, rainbow dye -> gold). Self-
// contained; the bound import only selects ES-module mode for the sandbox.
import htm from "htm";
void htm;
 
const HTML = `<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1" />
<title>Golden Splash</title>
<style>
  html,body{margin:0;height:100%;background:#050505;overflow:hidden;cursor:crosshair}
  #fluid{width:100vw;height:100vh;display:block}
  .hint{position:fixed;left:50%;bottom:26px;transform:translateX(-50%);z-index:2;pointer-events:none;
    font-family:ui-monospace,SFMono-Regular,Menlo,monospace;font-size:11px;letter-spacing:.34em;
    text-transform:uppercase;color:#7a6a3a}
  .hint b{color:#e8c24b;font-weight:600}
</style>
</head>
<body>
  <canvas id="fluid"></canvas>
  <div class="hint">move to <b>splash</b></div>
<script>
(function(){
  "use strict";
  const canvas = document.getElementById('fluid');
 
  function pointerPrototype() {
    this.id = -1; this.texcoordX = 0; this.texcoordY = 0;
    this.prevTexcoordX = 0; this.prevTexcoordY = 0;
    this.deltaX = 0; this.deltaY = 0; this.down = false; this.moved = false; this.color = [0,0,0];
  }
 
  let config = {
    SIM_RESOLUTION: 128,
    DYE_RESOLUTION: 1440,
    CAPTURE_RESOLUTION: 512,
    DENSITY_DISSIPATION: 2.6,
    VELOCITY_DISSIPATION: 2,
    PRESSURE: 0.1,
    PRESSURE_ITERATIONS: 20,
    CURL: 3.5,
    SPLAT_RADIUS: 0.22,
    SPLAT_FORCE: 6000,
    SHADING: true,
    COLOR_UPDATE_SPEED: 10,
    PAUSED: false,
    BACK_COLOR: { r: 0, g: 0, b: 0 },
    TRANSPARENT: true
  };
 
  let pointers = [new pointerPrototype()];
  const { gl, ext } = getWebGLContext(canvas);
  if (!ext.supportLinearFiltering) { config.DYE_RESOLUTION = 256; config.SHADING = false; }
 
  function getWebGLContext(canvas) {
    const params = { alpha: true, depth: false, stencil: false, antialias: false, preserveDrawingBuffer: false };
    let gl = canvas.getContext('webgl2', params);
    const isWebGL2 = !!gl;
    if (!isWebGL2) gl = canvas.getContext('webgl', params) || canvas.getContext('experimental-webgl', params);
    let halfFloat, supportLinearFiltering;
    if (isWebGL2) {
      gl.getExtension('EXT_color_buffer_float');
      supportLinearFiltering = gl.getExtension('OES_texture_float_linear');
    } else {
      halfFloat = gl.getExtension('OES_texture_half_float');
      supportLinearFiltering = gl.getExtension('OES_texture_half_float_linear');
    }
    gl.clearColor(0.0, 0.0, 0.0, 1.0);
    const halfFloatTexType = isWebGL2 ? gl.HALF_FLOAT : halfFloat && halfFloat.HALF_FLOAT_OES;
    let formatRGBA, formatRG, formatR;
    if (isWebGL2) {
      formatRGBA = getSupportedFormat(gl, gl.RGBA16F, gl.RGBA, halfFloatTexType);
      formatRG = getSupportedFormat(gl, gl.RG16F, gl.RG, halfFloatTexType);
      formatR = getSupportedFormat(gl, gl.R16F, gl.RED, halfFloatTexType);
    } else {
      formatRGBA = getSupportedFormat(gl, gl.RGBA, gl.RGBA, halfFloatTexType);
      formatRG = getSupportedFormat(gl, gl.RGBA, gl.RGBA, halfFloatTexType);
      formatR = getSupportedFormat(gl, gl.RGBA, gl.RGBA, halfFloatTexType);
    }
    return { gl, ext: { formatRGBA, formatRG, formatR, halfFloatTexType, supportLinearFiltering } };
  }
 
  function getSupportedFormat(gl, internalFormat, format, type) {
    if (!supportRenderTextureFormat(gl, internalFormat, format, type)) {
      switch (internalFormat) {
        case gl.R16F: return getSupportedFormat(gl, gl.RG16F, gl.RG, type);
        case gl.RG16F: return getSupportedFormat(gl, gl.RGBA16F, gl.RGBA, type);
        default: return null;
      }
    }
    return { internalFormat, format };
  }
 
  function supportRenderTextureFormat(gl, internalFormat, format, type) {
    const texture = gl.createTexture();
    gl.bindTexture(gl.TEXTURE_2D, texture);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
    gl.texImage2D(gl.TEXTURE_2D, 0, internalFormat, 4, 4, 0, format, type, null);
    const fbo = gl.createFramebuffer();
    gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
    gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);
    return gl.checkFramebufferStatus(gl.FRAMEBUFFER) === gl.FRAMEBUFFER_COMPLETE;
  }
 
  class Material {
    constructor(vertexShader, fragmentShaderSource) {
      this.vertexShader = vertexShader; this.fragmentShaderSource = fragmentShaderSource;
      this.programs = []; this.activeProgram = null; this.uniforms = [];
    }
    setKeywords(keywords) {
      let hash = 0;
      for (let i = 0; i < keywords.length; i++) hash += hashCode(keywords[i]);
      let program = this.programs[hash];
      if (program == null) {
        let fragmentShader = compileShader(gl.FRAGMENT_SHADER, this.fragmentShaderSource, keywords);
        program = createProgram(this.vertexShader, fragmentShader);
        this.programs[hash] = program;
      }
      if (program === this.activeProgram) return;
      this.uniforms = getUniforms(program); this.activeProgram = program;
    }
    bind() { gl.useProgram(this.activeProgram); }
  }
  class Program {
    constructor(vertexShader, fragmentShader) {
      this.uniforms = {}; this.program = createProgram(vertexShader, fragmentShader);
      this.uniforms = getUniforms(this.program);
    }
    bind() { gl.useProgram(this.program); }
  }
  function createProgram(vertexShader, fragmentShader) {
    let program = gl.createProgram();
    gl.attachShader(program, vertexShader); gl.attachShader(program, fragmentShader);
    gl.linkProgram(program);
    if (!gl.getProgramParameter(program, gl.LINK_STATUS)) console.trace(gl.getProgramInfoLog(program));
    return program;
  }
  function getUniforms(program) {
    let uniforms = [];
    let uniformCount = gl.getProgramParameter(program, gl.ACTIVE_UNIFORMS);
    for (let i = 0; i < uniformCount; i++) {
      let uniformName = gl.getActiveUniform(program, i).name;
      uniforms[uniformName] = gl.getUniformLocation(program, uniformName);
    }
    return uniforms;
  }
  function compileShader(type, source, keywords) {
    source = addKeywords(source, keywords);
    const shader = gl.createShader(type);
    gl.shaderSource(shader, source); gl.compileShader(shader);
    if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) console.trace(gl.getShaderInfoLog(shader));
    return shader;
  }
  function addKeywords(source, keywords) {
    if (!keywords) return source;
    let keywordsString = '';
    keywords.forEach(k => { keywordsString += '#define ' + k + '\\n'; });
    return keywordsString + source;
  }
 
  const baseVertexShader = compileShader(gl.VERTEX_SHADER, \`
    precision highp float;
    attribute vec2 aPosition;
    varying vec2 vUv; varying vec2 vL; varying vec2 vR; varying vec2 vT; varying vec2 vB;
    uniform vec2 texelSize;
    void main () {
      vUv = aPosition * 0.5 + 0.5;
      vL = vUv - vec2(texelSize.x, 0.0); vR = vUv + vec2(texelSize.x, 0.0);
      vT = vUv + vec2(0.0, texelSize.y); vB = vUv - vec2(0.0, texelSize.y);
      gl_Position = vec4(aPosition, 0.0, 1.0);
    }\`);
 
  const copyShader = compileShader(gl.FRAGMENT_SHADER, \`
    precision mediump float; precision mediump sampler2D;
    varying highp vec2 vUv; uniform sampler2D uTexture;
    void main () { gl_FragColor = texture2D(uTexture, vUv); }\`);
 
  const clearShader = compileShader(gl.FRAGMENT_SHADER, \`
    precision mediump float; precision mediump sampler2D;
    varying highp vec2 vUv; uniform sampler2D uTexture; uniform float value;
    void main () { gl_FragColor = value * texture2D(uTexture, vUv); }\`);
 
  const displayShaderSource = \`
    precision highp float; precision highp sampler2D;
    varying vec2 vUv; varying vec2 vL; varying vec2 vR; varying vec2 vT; varying vec2 vB;
    uniform sampler2D uTexture; uniform vec2 texelSize;
    void main () {
      vec3 c = texture2D(uTexture, vUv).rgb;
      #ifdef SHADING
        vec3 lc = texture2D(uTexture, vL).rgb; vec3 rc = texture2D(uTexture, vR).rgb;
        vec3 tc = texture2D(uTexture, vT).rgb; vec3 bc = texture2D(uTexture, vB).rgb;
        float dx = length(rc) - length(lc); float dy = length(tc) - length(bc);
        vec3 n = normalize(vec3(dx, dy, length(texelSize))); vec3 l = vec3(0.0, 0.0, 1.0);
        float diffuse = clamp(dot(n, l) + 0.7, 0.7, 1.0); c *= diffuse;
      #endif
      float a = max(c.r, max(c.g, c.b));
      gl_FragColor = vec4(c, a);
    }\`;
 
  const splatShader = compileShader(gl.FRAGMENT_SHADER, \`
    precision highp float; precision highp sampler2D;
    varying vec2 vUv; uniform sampler2D uTarget; uniform float aspectRatio;
    uniform vec3 color; uniform vec2 point; uniform float radius;
    void main () {
      vec2 p = vUv - point.xy; p.x *= aspectRatio;
      vec3 splat = exp(-dot(p, p) / radius) * color;
      vec3 base = texture2D(uTarget, vUv).xyz;
      gl_FragColor = vec4(base + splat, 1.0);
    }\`);
 
  const advectionShader = compileShader(gl.FRAGMENT_SHADER, \`
    precision highp float; precision highp sampler2D;
    varying vec2 vUv; uniform sampler2D uVelocity; uniform sampler2D uSource;
    uniform vec2 texelSize; uniform vec2 dyeTexelSize; uniform float dt; uniform float dissipation;
    vec4 bilerp (sampler2D sam, vec2 uv, vec2 tsize) {
      vec2 st = uv / tsize - 0.5; vec2 iuv = floor(st); vec2 fuv = fract(st);
      vec4 a = texture2D(sam, (iuv + vec2(0.5, 0.5)) * tsize);
      vec4 b = texture2D(sam, (iuv + vec2(1.5, 0.5)) * tsize);
      vec4 c = texture2D(sam, (iuv + vec2(0.5, 1.5)) * tsize);
      vec4 d = texture2D(sam, (iuv + vec2(1.5, 1.5)) * tsize);
      return mix(mix(a, b, fuv.x), mix(c, d, fuv.x), fuv.y);
    }
    void main () {
      #ifdef MANUAL_FILTERING
        vec2 coord = vUv - dt * bilerp(uVelocity, vUv, texelSize).xy * texelSize;
        vec4 result = bilerp(uSource, coord, dyeTexelSize);
      #else
        vec2 coord = vUv - dt * texture2D(uVelocity, vUv).xy * texelSize;
        vec4 result = texture2D(uSource, coord);
      #endif
      float decay = 1.0 + dissipation * dt;
      gl_FragColor = result / decay;
    }\`, ext.supportLinearFiltering ? null : ['MANUAL_FILTERING']);
 
  const divergenceShader = compileShader(gl.FRAGMENT_SHADER, \`
    precision mediump float; precision mediump sampler2D;
    varying highp vec2 vUv; varying highp vec2 vL; varying highp vec2 vR; varying highp vec2 vT; varying highp vec2 vB;
    uniform sampler2D uVelocity;
    void main () {
      float L = texture2D(uVelocity, vL).x; float R = texture2D(uVelocity, vR).x;
      float T = texture2D(uVelocity, vT).y; float B = texture2D(uVelocity, vB).y;
      vec2 C = texture2D(uVelocity, vUv).xy;
      if (vL.x < 0.0) { L = -C.x; } if (vR.x > 1.0) { R = -C.x; }
      if (vT.y > 1.0) { T = -C.y; } if (vB.y < 0.0) { B = -C.y; }
      float div = 0.5 * (R - L + T - B);
      gl_FragColor = vec4(div, 0.0, 0.0, 1.0);
    }\`);
 
  const curlShader = compileShader(gl.FRAGMENT_SHADER, \`
    precision mediump float; precision mediump sampler2D;
    varying highp vec2 vUv; varying highp vec2 vL; varying highp vec2 vR; varying highp vec2 vT; varying highp vec2 vB;
    uniform sampler2D uVelocity;
    void main () {
      float L = texture2D(uVelocity, vL).y; float R = texture2D(uVelocity, vR).y;
      float T = texture2D(uVelocity, vT).x; float B = texture2D(uVelocity, vB).x;
      float vorticity = R - L - T + B;
      gl_FragColor = vec4(0.5 * vorticity, 0.0, 0.0, 1.0);
    }\`);
 
  const vorticityShader = compileShader(gl.FRAGMENT_SHADER, \`
    precision highp float; precision highp sampler2D;
    varying vec2 vUv; varying vec2 vL; varying vec2 vR; varying vec2 vT; varying vec2 vB;
    uniform sampler2D uVelocity; uniform sampler2D uCurl; uniform float curl; uniform float dt;
    void main () {
      float L = texture2D(uCurl, vL).x; float R = texture2D(uCurl, vR).x;
      float T = texture2D(uCurl, vT).x; float B = texture2D(uCurl, vB).x; float C = texture2D(uCurl, vUv).x;
      vec2 force = 0.5 * vec2(abs(T) - abs(B), abs(R) - abs(L));
      force /= length(force) + 0.0001; force *= curl * C; force.y *= -1.0;
      vec2 velocity = texture2D(uVelocity, vUv).xy;
      velocity += force * dt; velocity = min(max(velocity, -1000.0), 1000.0);
      gl_FragColor = vec4(velocity, 0.0, 1.0);
    }\`);
 
  const pressureShader = compileShader(gl.FRAGMENT_SHADER, \`
    precision mediump float; precision mediump sampler2D;
    varying highp vec2 vUv; varying highp vec2 vL; varying highp vec2 vR; varying highp vec2 vT; varying highp vec2 vB;
    uniform sampler2D uPressure; uniform sampler2D uDivergence;
    void main () {
      float L = texture2D(uPressure, vL).x; float R = texture2D(uPressure, vR).x;
      float T = texture2D(uPressure, vT).x; float B = texture2D(uPressure, vB).x;
      float divergence = texture2D(uDivergence, vUv).x;
      float pressure = (L + R + B + T - divergence) * 0.25;
      gl_FragColor = vec4(pressure, 0.0, 0.0, 1.0);
    }\`);
 
  const gradientSubtractShader = compileShader(gl.FRAGMENT_SHADER, \`
    precision mediump float; precision mediump sampler2D;
    varying highp vec2 vUv; varying highp vec2 vL; varying highp vec2 vR; varying highp vec2 vT; varying highp vec2 vB;
    uniform sampler2D uPressure; uniform sampler2D uVelocity;
    void main () {
      float L = texture2D(uPressure, vL).x; float R = texture2D(uPressure, vR).x;
      float T = texture2D(uPressure, vT).x; float B = texture2D(uPressure, vB).x;
      vec2 velocity = texture2D(uVelocity, vUv).xy;
      velocity.xy -= vec2(R - L, T - B);
      gl_FragColor = vec4(velocity, 0.0, 1.0);
    }\`);
 
  const blit = (() => {
    gl.bindBuffer(gl.ARRAY_BUFFER, gl.createBuffer());
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([-1, -1, -1, 1, 1, 1, 1, -1]), gl.STATIC_DRAW);
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, gl.createBuffer());
    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array([0, 1, 2, 0, 2, 3]), gl.STATIC_DRAW);
    gl.vertexAttribPointer(0, 2, gl.FLOAT, false, 0, 0);
    gl.enableVertexAttribArray(0);
    return (target, clear = false) => {
      if (target == null) { gl.viewport(0, 0, gl.drawingBufferWidth, gl.drawingBufferHeight); gl.bindFramebuffer(gl.FRAMEBUFFER, null); }
      else { gl.viewport(0, 0, target.width, target.height); gl.bindFramebuffer(gl.FRAMEBUFFER, target.fbo); }
      if (clear) { gl.clearColor(0.0, 0.0, 0.0, 1.0); gl.clear(gl.COLOR_BUFFER_BIT); }
      gl.drawElements(gl.TRIANGLES, 6, gl.UNSIGNED_SHORT, 0);
    };
  })();
 
  let dye, velocity, divergence, curl, pressure;
  const copyProgram = new Program(baseVertexShader, copyShader);
  const clearProgram = new Program(baseVertexShader, clearShader);
  const splatProgram = new Program(baseVertexShader, splatShader);
  const advectionProgram = new Program(baseVertexShader, advectionShader);
  const divergenceProgram = new Program(baseVertexShader, divergenceShader);
  const curlProgram = new Program(baseVertexShader, curlShader);
  const vorticityProgram = new Program(baseVertexShader, vorticityShader);
  const pressureProgram = new Program(baseVertexShader, pressureShader);
  const gradienSubtractProgram = new Program(baseVertexShader, gradientSubtractShader);
  const displayMaterial = new Material(baseVertexShader, displayShaderSource);
 
  function initFramebuffers() {
    let simRes = getResolution(config.SIM_RESOLUTION);
    let dyeRes = getResolution(config.DYE_RESOLUTION);
    const texType = ext.halfFloatTexType;
    const rgba = ext.formatRGBA, rg = ext.formatRG, r = ext.formatR;
    const filtering = ext.supportLinearFiltering ? gl.LINEAR : gl.NEAREST;
    gl.disable(gl.BLEND);
    if (!dye) dye = createDoubleFBO(dyeRes.width, dyeRes.height, rgba.internalFormat, rgba.format, texType, filtering);
    else dye = resizeDoubleFBO(dye, dyeRes.width, dyeRes.height, rgba.internalFormat, rgba.format, texType, filtering);
    if (!velocity) velocity = createDoubleFBO(simRes.width, simRes.height, rg.internalFormat, rg.format, texType, filtering);
    else velocity = resizeDoubleFBO(velocity, simRes.width, simRes.height, rg.internalFormat, rg.format, texType, filtering);
    divergence = createFBO(simRes.width, simRes.height, r.internalFormat, r.format, texType, gl.NEAREST);
    curl = createFBO(simRes.width, simRes.height, r.internalFormat, r.format, texType, gl.NEAREST);
    pressure = createDoubleFBO(simRes.width, simRes.height, r.internalFormat, r.format, texType, gl.NEAREST);
  }
  function createFBO(w, h, internalFormat, format, type, param) {
    gl.activeTexture(gl.TEXTURE0);
    let texture = gl.createTexture();
    gl.bindTexture(gl.TEXTURE_2D, texture);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, param);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, param);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
    gl.texImage2D(gl.TEXTURE_2D, 0, internalFormat, w, h, 0, format, type, null);
    let fbo = gl.createFramebuffer();
    gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
    gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);
    gl.viewport(0, 0, w, h); gl.clear(gl.COLOR_BUFFER_BIT);
    let texelSizeX = 1.0 / w, texelSizeY = 1.0 / h;
    return { texture, fbo, width: w, height: h, texelSizeX, texelSizeY,
      attach(id) { gl.activeTexture(gl.TEXTURE0 + id); gl.bindTexture(gl.TEXTURE_2D, texture); return id; } };
  }
  function createDoubleFBO(w, h, internalFormat, format, type, param) {
    let fbo1 = createFBO(w, h, internalFormat, format, type, param);
    let fbo2 = createFBO(w, h, internalFormat, format, type, param);
    return { width: w, height: h, texelSizeX: fbo1.texelSizeX, texelSizeY: fbo1.texelSizeY,
      get read() { return fbo1; }, set read(v) { fbo1 = v; },
      get write() { return fbo2; }, set write(v) { fbo2 = v; },
      swap() { let t = fbo1; fbo1 = fbo2; fbo2 = t; } };
  }
  function resizeFBO(target, w, h, internalFormat, format, type, param) {
    let newFBO = createFBO(w, h, internalFormat, format, type, param);
    copyProgram.bind(); gl.uniform1i(copyProgram.uniforms.uTexture, target.attach(0)); blit(newFBO); return newFBO;
  }
  function resizeDoubleFBO(target, w, h, internalFormat, format, type, param) {
    if (target.width === w && target.height === h) return target;
    target.read = resizeFBO(target.read, w, h, internalFormat, format, type, param);
    target.write = createFBO(w, h, internalFormat, format, type, param);
    target.width = w; target.height = h; target.texelSizeX = 1.0 / w; target.texelSizeY = 1.0 / h;
    return target;
  }
  function updateKeywords() {
    let displayKeywords = [];
    if (config.SHADING) displayKeywords.push('SHADING');
    displayMaterial.setKeywords(displayKeywords);
  }
 
  updateKeywords(); initFramebuffers();
  let lastUpdateTime = Date.now(); let colorUpdateTimer = 0.0; let rafId;
 
  function updateFrame() {
    const dt = calcDeltaTime();
    if (resizeCanvas()) initFramebuffers();
    updateColors(dt); applyInputs(); step(dt); render(null);
    rafId = requestAnimationFrame(updateFrame);
  }
  function calcDeltaTime() {
    let now = Date.now(); let dt = (now - lastUpdateTime) / 1000; dt = Math.min(dt, 0.016666); lastUpdateTime = now; return dt;
  }
  function resizeCanvas() {
    let width = scaleByPixelRatio(canvas.clientWidth); let height = scaleByPixelRatio(canvas.clientHeight);
    if (canvas.width !== width || canvas.height !== height) { canvas.width = width; canvas.height = height; return true; }
    return false;
  }
  function updateColors(dt) {
    colorUpdateTimer += dt * config.COLOR_UPDATE_SPEED;
    if (colorUpdateTimer >= 1) { colorUpdateTimer = wrap(colorUpdateTimer, 0, 1); pointers.forEach(p => { p.color = generateColor(); }); }
  }
  function applyInputs() { pointers.forEach(p => { if (p.moved) { p.moved = false; splatPointer(p); } }); }
 
  function step(dt) {
    gl.disable(gl.BLEND);
    curlProgram.bind();
    gl.uniform2f(curlProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
    gl.uniform1i(curlProgram.uniforms.uVelocity, velocity.read.attach(0)); blit(curl);
    vorticityProgram.bind();
    gl.uniform2f(vorticityProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
    gl.uniform1i(vorticityProgram.uniforms.uVelocity, velocity.read.attach(0));
    gl.uniform1i(vorticityProgram.uniforms.uCurl, curl.attach(1));
    gl.uniform1f(vorticityProgram.uniforms.curl, config.CURL);
    gl.uniform1f(vorticityProgram.uniforms.dt, dt); blit(velocity.write); velocity.swap();
    divergenceProgram.bind();
    gl.uniform2f(divergenceProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
    gl.uniform1i(divergenceProgram.uniforms.uVelocity, velocity.read.attach(0)); blit(divergence);
    clearProgram.bind();
    gl.uniform1i(clearProgram.uniforms.uTexture, pressure.read.attach(0));
    gl.uniform1f(clearProgram.uniforms.value, config.PRESSURE); blit(pressure.write); pressure.swap();
    pressureProgram.bind();
    gl.uniform2f(pressureProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
    gl.uniform1i(pressureProgram.uniforms.uDivergence, divergence.attach(0));
    for (let i = 0; i < config.PRESSURE_ITERATIONS; i++) {
      gl.uniform1i(pressureProgram.uniforms.uPressure, pressure.read.attach(1)); blit(pressure.write); pressure.swap();
    }
    gradienSubtractProgram.bind();
    gl.uniform2f(gradienSubtractProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
    gl.uniform1i(gradienSubtractProgram.uniforms.uPressure, pressure.read.attach(0));
    gl.uniform1i(gradienSubtractProgram.uniforms.uVelocity, velocity.read.attach(1)); blit(velocity.write); velocity.swap();
    advectionProgram.bind();
    gl.uniform2f(advectionProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
    if (!ext.supportLinearFiltering) gl.uniform2f(advectionProgram.uniforms.dyeTexelSize, velocity.texelSizeX, velocity.texelSizeY);
    let velocityId = velocity.read.attach(0);
    gl.uniform1i(advectionProgram.uniforms.uVelocity, velocityId);
    gl.uniform1i(advectionProgram.uniforms.uSource, velocityId);
    gl.uniform1f(advectionProgram.uniforms.dt, dt);
    gl.uniform1f(advectionProgram.uniforms.dissipation, config.VELOCITY_DISSIPATION); blit(velocity.write); velocity.swap();
    if (!ext.supportLinearFiltering) gl.uniform2f(advectionProgram.uniforms.dyeTexelSize, dye.texelSizeX, dye.texelSizeY);
    gl.uniform1i(advectionProgram.uniforms.uVelocity, velocity.read.attach(0));
    gl.uniform1i(advectionProgram.uniforms.uSource, dye.read.attach(1));
    gl.uniform1f(advectionProgram.uniforms.dissipation, config.DENSITY_DISSIPATION); blit(dye.write); dye.swap();
  }
  function render(target) { gl.blendFunc(gl.ONE, gl.ONE_MINUS_SRC_ALPHA); gl.enable(gl.BLEND); drawDisplay(target); }
  function drawDisplay(target) {
    let width = target == null ? gl.drawingBufferWidth : target.width;
    let height = target == null ? gl.drawingBufferHeight : target.height;
    displayMaterial.bind();
    if (config.SHADING) gl.uniform2f(displayMaterial.uniforms.texelSize, 1.0 / width, 1.0 / height);
    gl.uniform1i(displayMaterial.uniforms.uTexture, dye.read.attach(0)); blit(target);
  }
  function splatPointer(pointer) {
    let dx = pointer.deltaX * config.SPLAT_FORCE; let dy = pointer.deltaY * config.SPLAT_FORCE;
    splat(pointer.texcoordX, pointer.texcoordY, dx, dy, pointer.color);
  }
  function clickSplat(pointer) {
    const color = generateColor(); color.r *= 10.0; color.g *= 10.0; color.b *= 10.0;
    let dx = 10 * (Math.random() - 0.5); let dy = 30 * (Math.random() - 0.5);
    splat(pointer.texcoordX, pointer.texcoordY, dx, dy, color);
  }
  function splat(x, y, dx, dy, color) {
    splatProgram.bind();
    gl.uniform1i(splatProgram.uniforms.uTarget, velocity.read.attach(0));
    gl.uniform1f(splatProgram.uniforms.aspectRatio, canvas.width / canvas.height);
    gl.uniform2f(splatProgram.uniforms.point, x, y);
    gl.uniform3f(splatProgram.uniforms.color, dx, dy, 0.0);
    gl.uniform1f(splatProgram.uniforms.radius, correctRadius(config.SPLAT_RADIUS / 100.0)); blit(velocity.write); velocity.swap();
    gl.uniform1i(splatProgram.uniforms.uTarget, dye.read.attach(0));
    gl.uniform3f(splatProgram.uniforms.color, color.r, color.g, color.b); blit(dye.write); dye.swap();
  }
  function correctRadius(radius) { let a = canvas.width / canvas.height; if (a > 1) radius *= a; return radius; }
  function multipleSplats(amount) {
    for (let i = 0; i < amount; i++) {
      const color = generateColor(); color.r *= 10; color.g *= 10; color.b *= 10;
      const x = Math.random(); const y = Math.random();
      const dx = 1000 * (Math.random() - 0.5); const dy = 1000 * (Math.random() - 0.5);
      splat(x, y, dx, dy, color);
    }
  }
  function updatePointerDownData(pointer, id, posX, posY) {
    pointer.id = id; pointer.down = true; pointer.moved = false;
    pointer.texcoordX = posX / canvas.width; pointer.texcoordY = 1.0 - posY / canvas.height;
    pointer.prevTexcoordX = pointer.texcoordX; pointer.prevTexcoordY = pointer.texcoordY;
    pointer.deltaX = 0; pointer.deltaY = 0; pointer.color = generateColor();
  }
  function updatePointerMoveData(pointer, posX, posY, color) {
    pointer.prevTexcoordX = pointer.texcoordX; pointer.prevTexcoordY = pointer.texcoordY;
    pointer.texcoordX = posX / canvas.width; pointer.texcoordY = 1.0 - posY / canvas.height;
    pointer.deltaX = correctDeltaX(pointer.texcoordX - pointer.prevTexcoordX);
    pointer.deltaY = correctDeltaY(pointer.texcoordY - pointer.prevTexcoordY);
    pointer.moved = Math.abs(pointer.deltaX) > 0 || Math.abs(pointer.deltaY) > 0; pointer.color = color;
  }
  function updatePointerUpData(pointer) { pointer.down = false; }
  function correctDeltaX(delta) { let a = canvas.width / canvas.height; if (a < 1) delta *= a; return delta; }
  function correctDeltaY(delta) { let a = canvas.width / canvas.height; if (a > 1) delta /= a; return delta; }
 
  // GOLDEN dye: amber/gold hues instead of the rainbow original
  function generateColor() {
    let h = 0.09 + Math.random() * 0.055;        // gold -> amber
    let c = HSVtoRGB(h, 0.92, 1.0);
    c.r *= 0.22; c.g *= 0.16; c.b *= 0.05;        // warm-weighted, a touch brighter than stock
    return c;
  }
  function HSVtoRGB(h, s, v) {
    let r, g, b, i, f, p, q, t;
    i = Math.floor(h * 6); f = h * 6 - i; p = v * (1 - s); q = v * (1 - f * s); t = v * (1 - (1 - f) * s);
    switch (i % 6) {
      case 0: r = v; g = t; b = p; break; case 1: r = q; g = v; b = p; break;
      case 2: r = p; g = v; b = t; break; case 3: r = p; g = q; b = v; break;
      case 4: r = t; g = p; b = v; break; case 5: r = v; g = p; b = q; break;
    }
    return { r, g, b };
  }
  function wrap(value, min, max) { const range = max - min; if (range === 0) return min; return ((value - min) % range) + min; }
  function getResolution(resolution) {
    let a = gl.drawingBufferWidth / gl.drawingBufferHeight; if (a < 1) a = 1.0 / a;
    const min = Math.round(resolution); const max = Math.round(resolution * a);
    if (gl.drawingBufferWidth > gl.drawingBufferHeight) return { width: max, height: min }; else return { width: min, height: max };
  }
  function scaleByPixelRatio(input) { const pr = window.devicePixelRatio || 1; return Math.floor(input * pr); }
  function hashCode(s) { if (s.length === 0) return 0; let hash = 0; for (let i = 0; i < s.length; i++) { hash = (hash << 5) - hash + s.charCodeAt(i); hash |= 0; } return hash; }
 
  function handleMouseDown(e) {
    let pointer = pointers[0]; let posX = scaleByPixelRatio(e.clientX); let posY = scaleByPixelRatio(e.clientY);
    updatePointerDownData(pointer, -1, posX, posY); clickSplat(pointer);
  }
  let firstMouseMoveHandled = false;
  function handleMouseMove(e) {
    let pointer = pointers[0]; let posX = scaleByPixelRatio(e.clientX); let posY = scaleByPixelRatio(e.clientY);
    if (!firstMouseMoveHandled) { let color = generateColor(); updatePointerMoveData(pointer, posX, posY, color); firstMouseMoveHandled = true; }
    else { updatePointerMoveData(pointer, posX, posY, pointer.color); }
  }
  function handleTouchStart(e) {
    const touches = e.targetTouches; let pointer = pointers[0];
    for (let i = 0; i < touches.length; i++) { let posX = scaleByPixelRatio(touches[i].clientX); let posY = scaleByPixelRatio(touches[i].clientY); updatePointerDownData(pointer, touches[i].identifier, posX, posY); }
  }
  function handleTouchMove(e) {
    const touches = e.targetTouches; let pointer = pointers[0];
    for (let i = 0; i < touches.length; i++) { let posX = scaleByPixelRatio(touches[i].clientX); let posY = scaleByPixelRatio(touches[i].clientY); updatePointerMoveData(pointer, posX, posY, pointer.color); }
  }
  function handleTouchEnd(e) { const touches = e.changedTouches; let pointer = pointers[0]; for (let i = 0; i < touches.length; i++) { updatePointerUpData(pointer); } }
 
  window.addEventListener('mousedown', handleMouseDown);
  window.addEventListener('mousemove', handleMouseMove);
  window.addEventListener('touchstart', handleTouchStart);
  window.addEventListener('touchmove', handleTouchMove, false);
  window.addEventListener('touchend', handleTouchEnd);
 
  multipleSplats(parseInt(String(Math.random() * 6)) + 8);   // golden burst on load
  updateFrame();
})();
</script>
</body>
</html>
`;
 
export default async function handler() {
  return new Response(HTML, { status: 200, headers: { "content-type": "text/html; charset=utf-8" } });
}
 
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