Underwater Caustics

A canvas and a module script, nothing to install. Set canvas.dataset.tps from your stream, or call canvas.token() once per token.

<canvas id="shader-underwater-caustics" data-tps="260" data-color="#2ee6d6" style="display:block;width:100%;height:240px;border-radius:12px"></canvas>
<script type="module">
  // Set canvas.dataset.tps from your stream, or call canvas.token() per token.
  const canvas = document.getElementById("shader-underwater-caustics");
  const gl = canvas.getContext("webgl2", { alpha: false, antialias: false });
  const fragment = `#version 300 es
precision highp float;
uniform vec3 iResolution;
uniform float iTime;
uniform float uTokens;
uniform float uTps;
uniform vec3 uColor;
out vec4 outColor;
// Gradient noise on a lattice that repeats every PER cells. Moving offsets are
// wrapped to whole periods, so the motion loops without a seam.
const float PER = 32.0;
// Octave turn and scale: an integer matrix keeps the lattice periodic.
const mat2 OCT = mat2(2.0, -1.0, 1.0, 2.0);

vec2 grad(vec2 i) {
  i = mod(i, PER);
  vec3 q = fract(vec3(i.xyx) * vec3(0.1031, 0.1030, 0.0973));
  q += dot(q, q.yzx + 33.33);
  return fract((q.xx + q.yz) * q.zy) * 2.0 - 1.0;
}

float noise(vec2 p) {
  vec2 i = floor(p), f = fract(p);
  vec2 u = f * f * f * (f * (f * 6.0 - 15.0) + 10.0);
  float a = dot(grad(i), f);
  float b = dot(grad(i + vec2(1.0, 0.0)), f - vec2(1.0, 0.0));
  float c = dot(grad(i + vec2(0.0, 1.0)), f - vec2(0.0, 1.0));
  float d = dot(grad(i + vec2(1.0, 1.0)), f - vec2(1.0, 1.0));
  return mix(mix(a, b, u.x), mix(c, d, u.x), u.y);
}

// A phase that climbs with x but wraps to the noise period.
float wrapP(float x) { return mod(x, PER); }

// Rotate a colour around the grey axis: hue shifts that follow uColor.
vec3 hue(vec3 c, float a) {
  const vec3 k = vec3(0.57735);
  float ca = cos(a);
  return c * ca + cross(k, c) * sin(a) + k * dot(k, c) * (1.0 - ca);
}

float hash12(vec2 p) {
  vec3 q = fract(vec3(p.xyx) * 0.1031);
  q += dot(q, q.yzx + 33.33);
  return fract((q.x + q.y) * q.z);
}

// Soft shoulder tone map plus a one step dither against banding.
vec3 finish(vec3 c, vec2 fc) {
  c = 1.0 - exp(-max(c, 0.0));
  return c + (hash12(fc) - 0.5) / 255.0;
}

// Distance to the nearest cell edge of a Voronoi net whose points sway.
float net(vec2 p, float ang) {
  vec2 i = floor(p), f = fract(p);
  float d1 = 8.0, d2 = 8.0;
  for (int y = -1; y <= 1; y++) {
    for (int x = -1; x <= 1; x++) {
      vec2 g = vec2(float(x), float(y));
      vec2 h = grad(i + g) * 0.5 + 0.5;
      float m = 1.0 + floor(h.y * 2.0);
      vec2 o = 0.5 + 0.38 * sin(vec2(ang * m, ang * (3.0 - m)) + 6.2831853 * h);
      vec2 r = g + o - f;
      float d = dot(r, r);
      if (d < d1) { d2 = d1; d1 = d; } else if (d < d2) { d2 = d; }
    }
  }
  return sqrt(d2) - sqrt(d1);
}

void mainImage(out vec4 fragColor, in vec2 fragCoord) {
  vec2 uv = (fragCoord - 0.5 * iResolution.xy) / iResolution.y;
  float e = 1.0 - exp(-uTps / 220.0);
  float a1 = mod(uTokens * 0.0042, 6.2831853) + mod(iTime * 0.25, 6.2831853);
  float a2 = mod(-uTokens * 0.0033, 6.2831853) + mod(iTime * 0.2, 6.2831853);
  vec2 wd = vec2(wrapP(uTokens * 0.0012) + wrapP(iTime * 0.03), wrapP(uTokens * 0.0008));
  vec2 ww = vec2(wrapP(uTokens * 0.0024) + wrapP(iTime * 0.04), -wrapP(uTokens * 0.0019));

  // the floor, seen at a slight tilt so the net shrinks toward the top
  vec2 fp = vec2(uv.x / (1.25 - 0.35 * uv.y), uv.y * 1.3);
  vec2 wq = vec2(noise(fp * 2.0 + ww), noise(fp * 2.0 + vec2(5.0, 3.0) - ww.yx));
  vec2 p1 = fp * 3.5 + wq * 1.1 + wd;
  vec2 p2 = fp * 5.0 - wq * 0.9 - wd.yx;
  float c1 = net(p1, a1);
  float c2 = net(p2, a2);
  // each channel focuses a little differently: a prism fringe along the lines
  vec3 k = vec3(0.7, 1.0, 1.35) * (5.0 + 7.0 * e);
  vec3 l1 = exp(-c1 * k);
  vec3 l2 = exp(-c2 * k * 1.2);
  vec3 caus = l1 * 0.55 + l2 * 0.4 + l1 * l2 * 2.6 + exp(-c1 * 2.5) * 0.1;
  // sunlight reaches the floor in patches as the swell above passes
  float patchy = 0.35 + 1.0 * smoothstep(-0.3, 0.35, noise(fp * 1.0 + vec2(3.0, 1.0) + ww.yx));

  float depth = smoothstep(-0.6, 0.55, uv.y);
  vec3 deep = mix(uColor * 0.07, hue(uColor, 0.35) * 0.015, depth);
  float sand = 0.85 + 0.15 * noise(fp * 9.0);
  vec3 light = mix(uColor, vec3(1.0), 0.35);
  vec3 col = deep * sand + light * caus * patchy * (0.42 + 0.75 * e) * (1.0 - depth * 0.55);

  // slanted god rays from the surface, drifting slowly
  float rx = uv.x + uv.y * 0.45;
  float rays = smoothstep(0.0, 0.55, noise(vec2(rx * 4.0 + wd.x, 0.5)) + 0.4 * noise(vec2(rx * 11.0 - wd.x, 2.5)));
  col += hue(uColor, 0.2) * rays * smoothstep(-0.55, 0.55, uv.y) * (0.1 + 0.1 * e);
  col += uColor * 0.06 * smoothstep(0.15, 0.6, uv.y);
  fragColor = vec4(finish(col, fragCoord), 1.0);
}

void main() {
  mainImage(outColor, gl_FragCoord.xy);
  outColor.a = 1.0;
}
`;
  const vertex = `#version 300 es
void main() {
  vec2 p = vec2((gl_VertexID << 1) & 2, gl_VertexID & 2);
  gl_Position = vec4(p * 2.0 - 1.0, 0.0, 1.0);
}
`;
  const compile = (type, src) => {
    const s = gl.createShader(type);
    gl.shaderSource(s, src);
    gl.compileShader(s);
    if (!gl.getShaderParameter(s, gl.COMPILE_STATUS)) throw new Error(gl.getShaderInfoLog(s));
    return s;
  };
  const program = gl.createProgram();
  gl.attachShader(program, compile(gl.VERTEX_SHADER, vertex));
  gl.attachShader(program, compile(gl.FRAGMENT_SHADER, fragment));
  gl.linkProgram(program);
  gl.useProgram(program);
  const u = (n) => gl.getUniformLocation(program, n);
  const [res, time, tokens, rate, color] = ["iResolution", "iTime", "uTokens", "uTps", "uColor"].map(u);
  const hex = parseInt((canvas.dataset.color || "#7c5cff").slice(1), 16);
  gl.uniform3f(color, ((hex >> 16) & 255) / 255, ((hex >> 8) & 255) / 255, (hex & 255) / 255);

  // canvas.token(): count real tokens and derive the rate from the last second.
  const stamps = [];
  canvas.token = () => {
    stamps.push(performance.now());
    canvas.dataset.tps = "auto";
  };
  const still = matchMedia("(prefers-reduced-motion: reduce)").matches;
  let count = 0, last = performance.now(), visible = true, frame = 0;
  new IntersectionObserver(([e]) => {
    visible = e.isIntersecting;
    if (visible && !frame) frame = requestAnimationFrame(draw);
  }).observe(canvas);

  function draw(now) {
    frame = 0;
    const dt = Math.min((now - last) / 1000, 0.1);
    last = now;
    while (stamps.length && now - stamps[0] > 1000) stamps.shift();
    const wobble = 1 + 0.25 * Math.sin(now / 588) + 0.15 * Math.sin(now / 233 + 1) + 0.08 * Math.sin(now / 91 + 2);
    const tps = canvas.dataset.tps === "auto" ? stamps.length : Number(canvas.dataset.tps) * wobble;
    count += tps * dt;
    const dpr = Math.min(devicePixelRatio || 1, 2);
    const w = Math.round(canvas.clientWidth * dpr), h = Math.round(canvas.clientHeight * dpr);
    if (canvas.width !== w || canvas.height !== h) { canvas.width = w; canvas.height = h; }
    gl.viewport(0, 0, w, h);
    gl.uniform3f(res, w, h, 1);
    gl.uniform1f(time, still ? 2 : now / 1000);
    gl.uniform1f(tokens, still ? Number(canvas.dataset.tps) * 2 : count);
    gl.uniform1f(rate, tps);
    gl.drawArrays(gl.TRIANGLES, 0, 3);
    if (visible && !still) frame = requestAnimationFrame(draw);
  }
  frame = requestAnimationFrame(draw);
</script>

// Inputs the site passes in, as constants for Shadertoy.
// uTps: tokens per second. uTokens: tokens so far. uColor: the accent.
#define uTps 260.0
#define uTokens (iTime * uTps)
#define uColor vec3(0.180, 0.902, 0.839)

// Gradient noise on a lattice that repeats every PER cells. Moving offsets are
// wrapped to whole periods, so the motion loops without a seam.
const float PER = 32.0;
// Octave turn and scale: an integer matrix keeps the lattice periodic.
const mat2 OCT = mat2(2.0, -1.0, 1.0, 2.0);

vec2 grad(vec2 i) {
  i = mod(i, PER);
  vec3 q = fract(vec3(i.xyx) * vec3(0.1031, 0.1030, 0.0973));
  q += dot(q, q.yzx + 33.33);
  return fract((q.xx + q.yz) * q.zy) * 2.0 - 1.0;
}

float noise(vec2 p) {
  vec2 i = floor(p), f = fract(p);
  vec2 u = f * f * f * (f * (f * 6.0 - 15.0) + 10.0);
  float a = dot(grad(i), f);
  float b = dot(grad(i + vec2(1.0, 0.0)), f - vec2(1.0, 0.0));
  float c = dot(grad(i + vec2(0.0, 1.0)), f - vec2(0.0, 1.0));
  float d = dot(grad(i + vec2(1.0, 1.0)), f - vec2(1.0, 1.0));
  return mix(mix(a, b, u.x), mix(c, d, u.x), u.y);
}

// A phase that climbs with x but wraps to the noise period.
float wrapP(float x) { return mod(x, PER); }

// Rotate a colour around the grey axis: hue shifts that follow uColor.
vec3 hue(vec3 c, float a) {
  const vec3 k = vec3(0.57735);
  float ca = cos(a);
  return c * ca + cross(k, c) * sin(a) + k * dot(k, c) * (1.0 - ca);
}

float hash12(vec2 p) {
  vec3 q = fract(vec3(p.xyx) * 0.1031);
  q += dot(q, q.yzx + 33.33);
  return fract((q.x + q.y) * q.z);
}

// Soft shoulder tone map plus a one step dither against banding.
vec3 finish(vec3 c, vec2 fc) {
  c = 1.0 - exp(-max(c, 0.0));
  return c + (hash12(fc) - 0.5) / 255.0;
}

// Distance to the nearest cell edge of a Voronoi net whose points sway.
float net(vec2 p, float ang) {
  vec2 i = floor(p), f = fract(p);
  float d1 = 8.0, d2 = 8.0;
  for (int y = -1; y <= 1; y++) {
    for (int x = -1; x <= 1; x++) {
      vec2 g = vec2(float(x), float(y));
      vec2 h = grad(i + g) * 0.5 + 0.5;
      float m = 1.0 + floor(h.y * 2.0);
      vec2 o = 0.5 + 0.38 * sin(vec2(ang * m, ang * (3.0 - m)) + 6.2831853 * h);
      vec2 r = g + o - f;
      float d = dot(r, r);
      if (d < d1) { d2 = d1; d1 = d; } else if (d < d2) { d2 = d; }
    }
  }
  return sqrt(d2) - sqrt(d1);
}

void mainImage(out vec4 fragColor, in vec2 fragCoord) {
  vec2 uv = (fragCoord - 0.5 * iResolution.xy) / iResolution.y;
  float e = 1.0 - exp(-uTps / 220.0);
  float a1 = mod(uTokens * 0.0042, 6.2831853) + mod(iTime * 0.25, 6.2831853);
  float a2 = mod(-uTokens * 0.0033, 6.2831853) + mod(iTime * 0.2, 6.2831853);
  vec2 wd = vec2(wrapP(uTokens * 0.0012) + wrapP(iTime * 0.03), wrapP(uTokens * 0.0008));
  vec2 ww = vec2(wrapP(uTokens * 0.0024) + wrapP(iTime * 0.04), -wrapP(uTokens * 0.0019));

  // the floor, seen at a slight tilt so the net shrinks toward the top
  vec2 fp = vec2(uv.x / (1.25 - 0.35 * uv.y), uv.y * 1.3);
  vec2 wq = vec2(noise(fp * 2.0 + ww), noise(fp * 2.0 + vec2(5.0, 3.0) - ww.yx));
  vec2 p1 = fp * 3.5 + wq * 1.1 + wd;
  vec2 p2 = fp * 5.0 - wq * 0.9 - wd.yx;
  float c1 = net(p1, a1);
  float c2 = net(p2, a2);
  // each channel focuses a little differently: a prism fringe along the lines
  vec3 k = vec3(0.7, 1.0, 1.35) * (5.0 + 7.0 * e);
  vec3 l1 = exp(-c1 * k);
  vec3 l2 = exp(-c2 * k * 1.2);
  vec3 caus = l1 * 0.55 + l2 * 0.4 + l1 * l2 * 2.6 + exp(-c1 * 2.5) * 0.1;
  // sunlight reaches the floor in patches as the swell above passes
  float patchy = 0.35 + 1.0 * smoothstep(-0.3, 0.35, noise(fp * 1.0 + vec2(3.0, 1.0) + ww.yx));

  float depth = smoothstep(-0.6, 0.55, uv.y);
  vec3 deep = mix(uColor * 0.07, hue(uColor, 0.35) * 0.015, depth);
  float sand = 0.85 + 0.15 * noise(fp * 9.0);
  vec3 light = mix(uColor, vec3(1.0), 0.35);
  vec3 col = deep * sand + light * caus * patchy * (0.42 + 0.75 * e) * (1.0 - depth * 0.55);

  // slanted god rays from the surface, drifting slowly
  float rx = uv.x + uv.y * 0.45;
  float rays = smoothstep(0.0, 0.55, noise(vec2(rx * 4.0 + wd.x, 0.5)) + 0.4 * noise(vec2(rx * 11.0 - wd.x, 2.5)));
  col += hue(uColor, 0.2) * rays * smoothstep(-0.55, 0.55, uv.y) * (0.1 + 0.1 * e);
  col += uColor * 0.06 * smoothstep(0.15, 0.6, uv.y);
  fragColor = vec4(finish(col, fragCoord), 1.0);
}

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