Kaleidoscope

// ═══ typeshade example — kaleidoscope (polar mirror fold) ═══
//
// The kaleidoscope fold: convert to polar, floor-mod the angle into one
// sector, mirror about the sector's midline, convert back — every sector now
// shows the same wedge of pattern, seamlessly. The pattern inside the wedge is
// swirling fbm + concentric rings through a cosine palette. The fold uses
// `mod` (#839), the portable FLOOR-mod, so the negative angles atan2
// produces wrap identically on both targets. WGSL + GLSL ES 3.00 (WebGL2).

import {
  fn,
  module,
  f32,
  vec2,
  vec3,
  vec4,
  sin,
  cos,
  floor,
  fract,
  mix,
  abs,
  mod,
  length,
  atan2,
  smoothstep,
  Let,
  f32T,
  vec2fT,
  u32,
  i32,
  u32T,
} from '../src/index.js';
import { VsOut, vs, fullscreenUniforms, screenCoords } from './_fullscreen.js';
import type { ShaderExample } from './_shared.js';
const U = fullscreenUniforms({ segments: f32T });

// An exact integer hash (lowbias32 with xxHash's primes): every target and the CPU oracle
// agree on every bit of it. `fract(sin(x) * 43758.5453)` did not, since WGSL bounds `sin`
// only to 2^-11 and the multiply puts that error above the fraction (#184).
const hash32 = fn('hash32', { x: u32T }, ({ x }) => {
  const a = Let(x.bitXor(x.shr(16)).mul(0x85ebca77));
  const b = Let(a.bitXor(a.shr(13)).mul(0xc2b2ae3d));
  return b.bitXor(b.shr(16));
});

// scalar hash of a lattice point → [0,1): 24 bits, which f32 holds exactly
const hash = fn('hash', { p: vec2fT }, ({ p }) => {
  const h = Let(hash32({ x: u32(i32(p.x)).bitXor(hash32({ x: u32(i32(p.y)) })) }));
  return f32(h.shr(8)).mul(5.9604644775390625e-8); // 2^-24, exact: WGSL lets `/` round
});

// bilinear value noise with smootherstep weights
const noise = fn('noise', { p: vec2fT }, ({ p }) => {
  const i = Let(floor(p));
  const f = Let(fract(p));
  const u = f.mul(f).mul(vec2(3).sub(f.mul(2)));
  return mix(
    mix(hash({ p: i }), hash({ p: i.add(vec2(1, 0)) }), u.x),
    mix(hash({ p: i.add(vec2(0, 1)) }), hash({ p: i.add(vec2(1, 1)) }), u.x),
    u.y,
  );
});

// 4-octave fbm, unrolled so the helper stays a pure value expression
const fbm = fn('fbm', { p: vec2fT }, ({ p }) => {
  return noise({ p })
    .mul(0.5)
    .add(noise({ p: p.mul(2.02) }).mul(0.25))
    .add(noise({ p: p.mul(4.08) }).mul(0.125))
    .add(noise({ p: p.mul(8.2) }).mul(0.0625));
});

const palette = fn('palette', { t: f32T }, ({ t }) => {
  const ph = vec3(0.0, 0.33, 0.67);
  return vec3(0.5).add(cos(t.add(ph).mul(6.283)).mul(0.5));
});

const fs = fn(
  'fs',
  { vo: VsOut },
  ({ vo }) => {
    const t = U.field.time;
    const res = U.field.resolution;
    const p = screenCoords(vo.uv, res);
    const r = Let(length(p));
    const a0 = Let(atan2(p.y, p.x));
    // fold: floor-mod the angle into one sector, mirror about its midline
    const sector = Let(f32(6.2831853).div(U.field.segments));
    const am = mod(a0, sector);
    const af = Let(abs(am.sub(sector.mul(0.5))));
    const q = vec2(cos(af), sin(af)).mul(r);
    // wedge pattern: swirling fbm + concentric rings
    const v = Let(fbm({ p: q.mul(3).add(vec2(t.mul(0.12), t.mul(0.09).neg())) }));
    const rings = sin(r.mul(9).sub(t.mul(0.8)))
      .mul(0.5)
      .add(0.5);
    const col = palette({ t: v.mul(0.7).add(rings.mul(0.15)).add(r.mul(0.3)).sub(t.mul(0.03)) });
    // the fbm field doubles as a brightness relief so the wedges keep depth
    const relief = v.mul(0.9).add(0.35);
    // vignette so the fold's outer edge fades instead of clipping
    const vig = f32(1).sub(smoothstep(0.55, 1.25, r));
    return vec4(col.mul(relief).mul(vig), 1);
  },
  { stage: 'fragment', retAttr: '@location(0)' },
);

const kaleidoscopeModule = module({
  structs: [U.struct, VsOut.decl],
  bindings: [U.binding],
  funcs: [vs, fs],
});

export const kaleidoscope: ShaderExample = {
  id: 'kaleidoscope',
  title: 'Kaleidoscope',
  blurb:
    'The polar mirror fold — the angle floor-modded into one sector and mirrored about its midline, so every sector repeats the same wedge of swirling fbm and rings. Segment count is live.',
  category: 'generic',
  file: 'kaleidoscope.ts',
  module: kaleidoscopeModule,
  renderable: true,
  controls: {
    time: { kind: 'time' },
    resolution: { kind: 'resolution' },
    segments: { kind: 'slider', label: 'Segments', min: 3, max: 12, step: 1, value: 6 },
  },
};

struct Uniforms {
  time: f32,
  resolution: vec2<f32>,
  segments: f32,
}

struct VsOut {
  @builtin(position) pos: vec4<f32>,
  @location(0) uv: vec2<f32>,
}

@group(0) @binding(0) var<uniform> U: Uniforms;

fn hash32(x: u32) -> u32 {
  let _v0 = ((x ^ (x >> 16u)) * 2246822519u);
  let _v1 = ((_v0 ^ (_v0 >> 13u)) * 3266489917u);
  return (_v1 ^ (_v1 >> 16u));
}

fn hash(p: vec2<f32>) -> f32 {
  let _v0 = hash32((u32(i32(p.x)) ^ hash32(u32(i32(p.y)))));
  return (f32((_v0 >> 8u)) * 5.960464477539063e-8);
}

fn noise(p: vec2<f32>) -> f32 {
  let _v0 = floor(p);
  let _v1 = fract(p);
  let _cse0 = vec2<f32>(3.0);
  let _gv0 = ((_v1 * _v1) * (_cse0 - (_v1 * 2.0)));
  let _lc0 = _gv0.x;
  return mix(mix(hash(_v0), hash((_v0 + vec2<f32>(1.0, 0.0))), _lc0), mix(hash((_v0 + vec2<f32>(0.0, 1.0))), hash((_v0 + vec2<f32>(1.0, 1.0))), _lc0), _gv0.y);
}

fn fbm(p: vec2<f32>) -> f32 {
  return ((((noise(p) * 0.5) + (noise((p * 2.02)) * 0.25)) + (noise((p * 4.08)) * 0.125)) + (noise((p * 8.2)) * 0.0625));
}

fn palette(t: f32) -> vec3<f32> {
  return (vec3<f32>(0.5) + (cos(((t + vec3<f32>(0.0, 0.33, 0.67)) * 6.283)) * 0.5));
}

@vertex
fn vs(@builtin(vertex_index) vi: u32) -> VsOut {
  let _cse0 = ((f32((vi & 1u)) * 4.0) - 1.0);
  let _cse1 = ((f32((vi >> 1u)) * 4.0) - 1.0);
  return VsOut(vec4<f32>(_cse0, _cse1, 0.0, 1.0), vec2<f32>(((_cse0 * 0.5) + 0.5), ((_cse1 * 0.5) + 0.5)));
}

@fragment
fn fs(vo: VsOut) -> @location(0) vec4<f32> {
  let _cse0 = vec2<f32>((((vo.uv.x * 2.0) - 1.0) * (U.resolution.x / U.resolution.y)), ((vo.uv.y * 2.0) - 1.0));
  let _v0 = length(_cse0);
  let _v1 = atan2(_cse0.y, _cse0.x);
  let _v2 = (6.2831853 / U.segments);
  let _v3 = abs(((_v1 - _v2 * floor(_v1 / _v2)) - (_v2 * 0.5)));
  let _v4 = fbm((((vec2<f32>(cos(_v3), sin(_v3)) * _v0) * 3.0) + vec2<f32>((U.time * 0.12), (-(U.time * 0.09)))));
  return vec4<f32>(((palette(((((_v4 * 0.7) + (((sin(((_v0 * 9.0) - (U.time * 0.8))) * 0.5) + 0.5) * 0.15)) + (_v0 * 0.3)) - (U.time * 0.03))) * ((_v4 * 0.9) + 0.35)) * (1.0 - smoothstep(0.55, 1.25, _v0))), 1.0);
}

#version 300 es
precision highp float;
precision highp int;

out vec2 uv;

void main() {
  uint vi = uint(gl_VertexID);
  float _cse0 = ((float((vi & 1u)) * 4.0) - 1.0);
  float _cse1 = ((float((vi >> 1u)) * 4.0) - 1.0);
  gl_Position = vec4(_cse0, _cse1, 0.0, 1.0);
  uv = vec2(((_cse0 * 0.5) + 0.5), ((_cse1 * 0.5) + 0.5));
}

#version 300 es
precision highp float;
precision highp int;

layout(std140) uniform Uniforms {
  float time;
  vec2 resolution;
  float segments;
} U;
int _f2i(float x) {
  return int(mix(clamp(x, -2147483648.0, 2147483520.0), 0.0, isnan(x)));
}
uint hash32(uint x) {
  uint _v0 = ((x ^ (x >> 16u)) * 2246822519u);
  uint _v1 = ((_v0 ^ (_v0 >> 13u)) * 3266489917u);
  return (_v1 ^ (_v1 >> 16u));
}

float hash(vec2 p) {
  uint _v0 = hash32((uint(_f2i(p.x)) ^ hash32(uint(_f2i(p.y)))));
  return (float((_v0 >> 8u)) * 5.960464477539063e-8);
}

float noise(vec2 p) {
  vec2 _v0 = floor(p);
  vec2 _v1 = fract(p);
  vec2 _cse0 = vec2(3.0);
  vec2 _gv0 = ((_v1 * _v1) * (_cse0 - (_v1 * 2.0)));
  float _lc0 = _gv0.x;
  return mix(mix(hash(_v0), hash((_v0 + vec2(1.0, 0.0))), _lc0), mix(hash((_v0 + vec2(0.0, 1.0))), hash((_v0 + vec2(1.0, 1.0))), _lc0), _gv0.y);
}

float fbm(vec2 p) {
  return ((((noise(p) * 0.5) + (noise((p * 2.02)) * 0.25)) + (noise((p * 4.08)) * 0.125)) + (noise((p * 8.2)) * 0.0625));
}

vec3 palette(float t) {
  return (vec3(0.5) + (cos(((t + vec3(0.0, 0.33, 0.67)) * 6.283)) * 0.5));
}
in vec2 uv;
layout(location = 0) out vec4 _ret;

void main() {
  vec2 _cse0 = vec2((((uv.x * 2.0) - 1.0) * (U.resolution.x / U.resolution.y)), ((uv.y * 2.0) - 1.0));
  float _v0 = length(_cse0);
  float _v1 = atan(_cse0.y, _cse0.x);
  float _v2 = (6.2831853 / U.segments);
  float _v3 = abs((mod(_v1, _v2) - (_v2 * 0.5)));
  float _v4 = fbm((((vec2(cos(_v3), sin(_v3)) * _v0) * 3.0) + vec2((U.time * 0.12), (-(U.time * 0.09)))));
  _ret = vec4(((palette(((((_v4 * 0.7) + (((sin(((_v0 * 9.0) - (U.time * 0.8))) * 0.5) + 0.5) * 0.15)) + (_v0 * 0.3)) - (U.time * 0.03))) * ((_v4 * 0.9) + 0.35)) * (1.0 - smoothstep(0.55, 1.25, _v0))), 1.0);
}