Dithered Waves

Installation#

CLI

npx shadcn@latest add https://hantui-theta.vercel.app/r/dithered-waves.json

Manual

1. Install the dependencies

   npmpnpmbunyarn

   npm install clsx tailwind-merge

2. Add the shared helpers

   Components use cn() from lib/utils.ts and the motion tokens below. See Installation if you have not set them up yet.

   lib/color.ts

   export type Vec3 = [r: number, g: number, b: number];
   
   /**
    * Parses #rgb, #rrggbb or #rrggbbaa (alpha is ignored) into 0–255 channels.
    * Anything else falls back to black, so a typo never crashes a shader.
    */
   export function hexToRgb(hex: string): Vec3 {
     let value = hex.trim().replace(/^#/, "");
     if (value.length === 3 || value.length === 4) value = [...value.slice(0, 3)].map((c) => c + c).join("");
     if (!/^[\da-f]{6}([\da-f]{2})?$/i.test(value)) return [0, 0, 0];
     const n = Number.parseInt(value.slice(0, 6), 16);
     return [(n >> 16) & 255, (n >> 8) & 255, n & 255];
   }
   
   /** Hex color as a normalized vec3 (each channel 0–1) for shader uniforms. */
   export function hexToVec3(hex: string): Vec3 {
     const [r, g, b] = hexToRgb(hex);
     return [r / 255, g / 255, b / 255];
   }
   
   /**
    * Any CSS color the browser understands (hex, rgb(), oklch(), color-mix() or a variable such as
    * `var(--primary)`) as 0–255 channels, computed in the context of `element` so theme variables
    * resolve. Hex takes a fast path; everything else is computed once per call, so cache the result
    * instead of calling this every frame. Browser only; unreadable values fall back to black.
    */
   export function cssColorToRgb(color: string, element: Element): Vec3 {
     const value = color.trim();
     if (/^#[\da-f]{3,8}$/i.test(value)) return hexToRgb(value);
     // Children of a canvas still get computed styles, but a regular parent is the safer host.
     const host = element instanceof HTMLCanvasElement ? (element.parentElement ?? document.body) : element;
     const probe = document.createElement("span");
     probe.style.cssText = "position:absolute;width:0;height:0;overflow:hidden;visibility:hidden";
     probe.style.color = value;
     host.appendChild(probe);
     const computed = getComputedStyle(probe).color;
     probe.remove();
     // A 1×1 canvas turns any computed color space (oklch, color(srgb …)) into sRGB bytes.
     const ctx = document.createElement("canvas").getContext("2d", { willReadFrequently: true });
     if (!ctx) return [0, 0, 0];
     ctx.fillStyle = "#000";
     ctx.fillStyle = computed;
     ctx.fillRect(0, 0, 1, 1);
     const [r, g, b] = ctx.getImageData(0, 0, 1, 1).data;
     return [r, g, b];
   }
   
   /**
    * Calls `onChange` when the page theme may have changed: a class or data-theme change on <html> or
    * <body> (shadcn's `.dark`, next-themes, a data-theme switch) or a change of the OS color scheme.
    * Resolved colors are cached, so re-resolve them here. Browser only; returns the unsubscribe.
    */
   export function observeTheme(onChange: () => void): () => void {
     const observer = new MutationObserver(onChange);
     const options = { attributes: true, attributeFilter: ["class", "data-theme"] };
     observer.observe(document.documentElement, options);
     if (document.body) observer.observe(document.body, options);
     const scheme = window.matchMedia("(prefers-color-scheme: dark)");
     scheme.addEventListener("change", onChange);
     return () => {
       observer.disconnect();
       scheme.removeEventListener("change", onChange);
     };
   }
   
   /** `cssColorToRgb` as a normalized vec3 (each channel 0–1) for shader uniforms. */
   export function cssColorToVec3(color: string, element: Element): Vec3 {
     const [r, g, b] = cssColorToRgb(color, element);
     return [r / 255, g / 255, b / 255];
   }
   
   const toLinear = (c: number) => (c <= 0.04045 ? c / 12.92 : ((c + 0.055) / 1.055) ** 2.4);
   const toGamma = (c: number) => (c <= 0.0031308 ? 12.92 * c : 1.055 * c ** (1 / 2.4) - 0.055);
   
   /** 0–255 sRGB to OKLCH: lightness 0–1, chroma, hue in radians. */
   export function rgbToOklch([r, g, b]: Vec3): Vec3 {
     const [lr, lg, lb] = [r, g, b].map((v) => toLinear(v / 255));
     const l = Math.cbrt(0.4122214708 * lr + 0.5363325363 * lg + 0.0514459929 * lb);
     const m = Math.cbrt(0.2119034982 * lr + 0.6806995451 * lg + 0.1073969566 * lb);
     const s = Math.cbrt(0.0883024619 * lr + 0.2817188376 * lg + 0.6299787005 * lb);
     const L = 0.2104542553 * l + 0.793617785 * m - 0.0040720468 * s;
     const A = 1.9779984951 * l - 2.428592205 * m + 0.4505937099 * s;
     const B = 0.0259040371 * l + 0.7827717662 * m - 0.808675766 * s;
     return [L, Math.hypot(A, B), Math.atan2(B, A)];
   }
   
   /** OKLCH back to 0–255 sRGB, clamped into gamut. */
   export function oklchToRgb([L, C, h]: Vec3): Vec3 {
     const A = C * Math.cos(h);
     const B = C * Math.sin(h);
     const l = (L + 0.3963377774 * A + 0.2158037573 * B) ** 3;
     const m = (L - 0.1055613458 * A - 0.0638541728 * B) ** 3;
     const s = (L - 0.0894841775 * A - 1.291485548 * B) ** 3;
     const rgb = [4.0767416621 * l - 3.3077115913 * m + 0.2309699292 * s, -1.2684380046 * l + 2.6097574011 * m - 0.3413193965 * s, -0.0041960863 * l - 0.7034186147 * m + 1.707614701 * s];
     return rgb.map((v) => Math.round(Math.min(1, Math.max(0, toGamma(Math.min(1, Math.max(0, v))))) * 255)) as Vec3;
   }
   
   /**
    * Mixes two 0–255 colors in OKLCH, taking the short way around the hue circle, so midpoints keep
    * their chroma instead of turning muddy the way an RGB mix does.
    */
   export function mixOklch(a: Vec3, b: Vec3, t: number): Vec3 {
     const [L1, C1, h1] = rgbToOklch(a);
     const [L2, C2, h2] = rgbToOklch(b);
     // A near-gray end has no meaningful hue: borrow the other end's.
     const ha = C1 < 0.02 ? h2 : h1;
     const hb = C2 < 0.02 ? h1 : h2;
     let dh = hb - ha;
     if (dh > Math.PI) dh -= Math.PI * 2;
     if (dh < -Math.PI) dh += Math.PI * 2;
     return oklchToRgb([L1 + (L2 - L1) * t, C1 + (C2 - C1) * t, ha + dh * t]);
   }

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   lib/webgl/noise.glsl.ts

   /**
    * Shared GLSL ES 3.00 snippets. Concatenate the ones a shader needs before its main():
    *
    *   const fragment = `${GLSL_HASH}${GLSL_SIMPLEX}${GLSL_FBM} void main() { … }`;
    *
    * GLSL_SIMPLEX needs GLSL_HASH, and GLSL_FBM needs GLSL_SIMPLEX.
    */
   
   /** Sine-free hashes: stable across GPUs, no visible banding. */
   export const GLSL_HASH = /* glsl */ `
   float hash12(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);
   }
   
   vec2 hash22(vec2 p) {
     vec3 p3 = fract(vec3(p.xyx) * vec3(0.1031, 0.1030, 0.0973));
     p3 += dot(p3, p3.yzx + 33.33);
     return fract((p3.xx + p3.yz) * p3.zy);
   }
   `;
   
   /** 2D simplex noise in roughly [-1, 1]. */
   export const GLSL_SIMPLEX = /* glsl */ `
   vec2 simplexGradient(vec2 cell) {
     float angle = hash12(cell) * 6.28318530718;
     return vec2(cos(angle), sin(angle));
   }
   
   float snoise(vec2 p) {
     const float F2 = 0.36602540378; // (sqrt(3) - 1) / 2
     const float G2 = 0.21132486540; // (3 - sqrt(3)) / 6
     vec2 cell = floor(p + (p.x + p.y) * F2);
     vec2 a = p - cell + (cell.x + cell.y) * G2;
     vec2 step1 = a.x > a.y ? vec2(1.0, 0.0) : vec2(0.0, 1.0);
     vec2 b = a - step1 + G2;
     vec2 c = a - 1.0 + 2.0 * G2;
     vec3 falloff = max(0.5 - vec3(dot(a, a), dot(b, b), dot(c, c)), 0.0);
     falloff *= falloff;
     falloff *= falloff;
     vec3 contribution = vec3(
       dot(a, simplexGradient(cell)),
       dot(b, simplexGradient(cell + step1)),
       dot(c, simplexGradient(cell + 1.0))
     );
     return 70.0 * dot(falloff, contribution);
   }
   `;
   
   /** Fractal Brownian motion over simplex noise; octaves is clamped to 1–8. Roughly [-1, 1]. */
   export const GLSL_FBM = /* glsl */ `
   float fbm(vec2 p, int octaves) {
     const mat2 rotate = mat2(0.8, 0.6, -0.6, 0.8);
     float sum = 0.0;
     float amplitude = 0.5;
     for (int i = 0; i < 8; i++) {
       if (i >= octaves) break;
       sum += amplitude * snoise(p);
       p = rotate * p * 2.03 + 17.1;
       amplitude *= 0.5;
     }
     return sum;
   }
   `;
   
   /** Ordered (Bayer) dither thresholds in [0, 1) for 2×2, 4×4 and 8×8 matrices. Pass pixel coordinates. */
   export const GLSL_BAYER = /* glsl */ `
   float bayer2(vec2 a) {
     a = floor(a);
     return fract(a.x * 0.5 + a.y * a.y * 0.75);
   }
   
   float bayer4(vec2 a) {
     return bayer2(0.5 * a) * 0.25 + bayer2(a);
   }
   
   float bayer8(vec2 a) {
     return bayer4(0.5 * a) * 0.25 + bayer2(a);
   }
   `;
   
   /** Hash, simplex and fBm together, in dependency order. */
   export const GLSL_NOISE = GLSL_HASH + GLSL_SIMPLEX + GLSL_FBM;

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   lib/webgl/use-shader-canvas.ts

   import { useEffect, useRef, useState } from "react";
   
   /** Numbers, vectors (arrays) and, for sampler2D uniforms, an image, canvas or video element. */
   export type UniformValue = number | boolean | readonly number[] | Float32Array | TexImageSource;
   
   const isTextureSource = (value: UniformValue): value is TexImageSource =>
     typeof value === "object" && value !== null && !Array.isArray(value) && !ArrayBuffer.isView(value);
   
   /**
    * - `idle`: not started yet (always the value on the server and the first client render)
    * - `running`: animating
    * - `static`: a single frame is on screen (reduced motion, paused, offscreen or tab hidden)
    * - `fallback`: WebGL2 is unavailable, the shader failed to compile or the context was lost
    */
   export type ShaderStatus = "idle" | "running" | "static" | "fallback";
   
   export interface UseShaderCanvasOptions {
     /**
      * Fragment shader source. Unless it starts with `#version`, the hook prepends a header with
      * `precision highp float`, the built-in uniforms `u_time` (seconds), `u_resolution` (pixels),
      * `u_mouse` (0–1, y up) and `u_pointer` (0–1, eases to 1 while the pointer is inside),
      * `in vec2 v_uv` and `out vec4 fragColor`. Output premultiplied alpha.
      */
     fragmentShader: string;
     /**
      * Custom uniforms by name. Read every frame, so updating them never restarts the shader. Pass a
      * function to compute them per frame from refs or other values that change without re-rendering.
      */
     uniforms?: Record<string, UniformValue> | (() => Record<string, UniformValue>);
     /** Clock multiplier. @default 1 */
     speed?: number;
     /** Freezes the clock and keeps the current frame on screen. @default false */
     paused?: boolean;
     /** Fraction of the display resolution to render at, clamped to 0.5–1. @default 1 */
     renderScale?: number;
     /** Highest device pixel ratio used. @default 1.5 */
     maxDpr?: number;
     /** Track the pointer over the container into `u_mouse` and `u_pointer`. @default false */
     pointer?: boolean;
     /** Clock value, in seconds, of the single frame drawn under reduced motion. @default 6 */
     staticTime?: number;
     /**
      * Render even on software WebGL (SwiftShader, llvmpipe), where compiling and every frame run on
      * the CPU and block the main thread. By default those renderers get the fallback. @default false
      */
     allowSoftware?: boolean;
   }
   
   const VERTEX_SHADER = /* glsl */ `#version 300 es
   out vec2 v_uv;
   void main() {
     vec2 p = vec2(float((gl_VertexID << 1) & 2), float(gl_VertexID & 2));
     v_uv = p;
     gl_Position = vec4(p * 2.0 - 1.0, 0.0, 1.0);
   }`;
   
   const FRAGMENT_HEADER = /* glsl */ `#version 300 es
   precision highp float;
   uniform float u_time;
   uniform vec2 u_resolution;
   uniform vec2 u_mouse;
   uniform float u_pointer;
   in vec2 v_uv;
   out vec4 fragColor;
   `;
   
   interface UniformSlot {
     location: WebGLUniformLocation;
     type: number;
   }
   
   const clamp = (value: number, min: number, max: number) => Math.min(max, Math.max(min, value));
   
   function compile(gl: WebGL2RenderingContext, type: number, source: string) {
     const shader = gl.createShader(type);
     if (!shader) return null;
     gl.shaderSource(shader, source);
     gl.compileShader(shader);
     if (gl.getShaderParameter(shader, gl.COMPILE_STATUS)) return shader;
     if (process.env.NODE_ENV !== "production") console.error(`useShaderCanvas: shader failed to compile\n${gl.getShaderInfoLog(shader)}`);
     gl.deleteShader(shader);
     return null;
   }
   
   function link(gl: WebGL2RenderingContext, fragmentSource: string) {
     const source = fragmentSource.trimStart().startsWith("#version") ? fragmentSource.trimStart() : FRAGMENT_HEADER + fragmentSource;
     const vertex = compile(gl, gl.VERTEX_SHADER, VERTEX_SHADER);
     const fragment = compile(gl, gl.FRAGMENT_SHADER, source);
     const program = vertex && fragment ? gl.createProgram() : null;
     if (program && vertex && fragment) {
       gl.attachShader(program, vertex);
       gl.attachShader(program, fragment);
       gl.linkProgram(program);
       gl.detachShader(program, vertex);
       gl.detachShader(program, fragment);
     }
     if (vertex) gl.deleteShader(vertex);
     if (fragment) gl.deleteShader(fragment);
     if (!program) return null;
     if (gl.getProgramParameter(program, gl.LINK_STATUS)) return program;
     if (process.env.NODE_ENV !== "production") console.error(`useShaderCanvas: program failed to link\n${gl.getProgramInfoLog(program)}`);
     gl.deleteProgram(program);
     return null;
   }
   
   function collectUniforms(gl: WebGL2RenderingContext, program: WebGLProgram) {
     const slots = new Map<string, UniformSlot>();
     const count = gl.getProgramParameter(program, gl.ACTIVE_UNIFORMS) as number;
     for (let i = 0; i < count; i++) {
       const info = gl.getActiveUniform(program, i);
       const location = info && gl.getUniformLocation(program, info.name);
       if (info && location) slots.set(info.name.replace(/\[0\]$/, ""), { location, type: info.type });
     }
     return slots;
   }
   
   function setUniform(gl: WebGL2RenderingContext, { location, type }: UniformSlot, value: Exclude<UniformValue, TexImageSource>) {
     const isInt = type === gl.INT || type === gl.BOOL;
     if (typeof value === "boolean" || typeof value === "number") {
       const n = Number(value);
       if (isInt) gl.uniform1i(location, n);
       else gl.uniform1f(location, n);
       return;
     }
     const list = value as number[] | Float32Array;
     if (isInt) gl.uniform1iv(location, Int32Array.from(list));
     else if (type === gl.FLOAT_VEC2) gl.uniform2fv(location, list);
     else if (type === gl.FLOAT_VEC3) gl.uniform3fv(location, list);
     else if (type === gl.FLOAT_VEC4) gl.uniform4fv(location, list);
     else gl.uniform1fv(location, list);
   }
   
   /**
    * Renders a fragment shader with WebGL2 on a canvas the hook creates inside the element you
    * attach `ref` to (give that element a size and `position: relative`, `absolute` or `fixed`).
    *
    * One fullscreen triangle, no three.js. The canvas follows the element's size, caps the pixel
    * ratio, pauses offscreen and in hidden tabs, draws a single static frame under reduced motion
    * (software WebGL such as SwiftShader gets the fallback unless allowSoftware is set),
    * recovers from context loss and releases the GPU context on unmount. Uniform values can be
    * numbers, arrays (vec2–vec4 or float arrays) or, for sampler2D uniforms, an image, canvas or
    * video element (uploaded once it has pixels; pass a new element or re-render to refresh). When `status` is
    * `fallback` (or before the first frame), whatever you render behind the canvas shows through.
    */
   export function useShaderCanvas<T extends HTMLElement = HTMLDivElement>(options: UseShaderCanvasOptions) {
     const ref = useRef<T>(null);
     const [status, setStatus] = useState<ShaderStatus>("idle");
     const latest = useRef(options);
     const wake = useRef<() => void>(() => {});
     const time = useRef(0);
   
     // Keep the render loop reading fresh props, and let it react to paused/uniform changes.
     useEffect(() => {
       latest.current = options;
       wake.current();
     });
   
     const { fragmentShader } = options;
   
     useEffect(() => {
       const host = ref.current;
       if (!host) return;
   
       const canvas = document.createElement("canvas");
       canvas.setAttribute("aria-hidden", "true");
       Object.assign(canvas.style, {
         position: "absolute",
         inset: "0",
         width: "100%",
         height: "100%",
         display: "block",
         pointerEvents: "none",
         opacity: "0",
         transition: "opacity 500ms ease-out",
       });
       host.appendChild(canvas);
   
       const reducedMotion = window.matchMedia("(prefers-reduced-motion: reduce)");
       const mouse = [0.5, 0.5];
       const mouseTarget = [0.5, 0.5];
       let gl: WebGL2RenderingContext | null = null;
       let program: WebGLProgram | null = null;
       let uniforms = new Map<string, UniformSlot>();
       const textures = new Map<string, { texture: WebGLTexture; unit: number; source: TexImageSource | null; ready: boolean }>();
       let reported: ShaderStatus = "idle";
       let raf = 0;
       let lastFrame = 0;
       let clock = 0;
       let pointer = 0;
       let pointerTarget = 0;
       let inView = false;
       let pageVisible = document.visibilityState === "visible";
       let needsResize = true;
       let drawn = false;
       let lost = false;
       let software = false;
   
       const report = (next: ShaderStatus) => {
         if (next === reported) return;
         reported = next;
         setStatus(next);
       };
   
       const build = () => {
         gl ??= canvas.getContext("webgl2", {
           alpha: true,
           antialias: false,
           depth: false,
           stencil: false,
           premultipliedAlpha: true,
           powerPreference: "low-power",
         });
         if (gl) {
           const info = gl.getExtension("WEBGL_debug_renderer_info");
           const renderer = info ? String(gl.getParameter(info.UNMASKED_RENDERER_WEBGL)) : String(gl.getParameter(gl.RENDERER));
           software = /swiftshader|llvmpipe|softpipe|software|basic render/i.test(renderer);
         }
         // On software WebGL even compiling blocks the main thread, so use the CSS fallback instead.
         program = gl && !(software && !latest.current.allowSoftware) ? link(gl, fragmentShader) : null;
         uniforms = gl && program ? collectUniforms(gl, program) : new Map();
         textures.clear();
         needsResize = true;
         return program !== null;
       };
   
       const resize = () => {
         if (!gl) return;
         const { renderScale = 1, maxDpr = 1.5 } = latest.current;
         const scale = Math.min(window.devicePixelRatio || 1, maxDpr) * clamp(renderScale, 0.5, 1);
         const width = Math.max(1, Math.round(host.clientWidth * scale));
         const height = Math.max(1, Math.round(host.clientHeight * scale));
         if (canvas.width !== width || canvas.height !== height) {
           canvas.width = width;
           canvas.height = height;
         }
         gl.viewport(0, 0, width, height);
         needsResize = false;
       };
   
       const draw = (time: number) => {
         if (!gl || !program || lost) return;
         if (needsResize) resize();
         gl.useProgram(program);
         const set = (name: string, value: UniformValue) => {
           const slot = uniforms.get(name);
           if (!slot || !gl) return;
           if (isTextureSource(value)) bindTexture(name, slot, value);
           else setUniform(gl, slot, value);
         };
         set("u_time", time);
         set("u_resolution", [canvas.width, canvas.height]);
         set("u_mouse", mouse);
         set("u_pointer", pointer);
         const source = latest.current.uniforms;
         const custom = typeof source === "function" ? source() : source;
         if (custom) for (const name in custom) set(name, custom[name]);
         gl.drawArrays(gl.TRIANGLES, 0, 3);
         if (!drawn) {
           drawn = true;
           canvas.style.opacity = "1";
         }
       };
   
       // Textures upload once per source (and every frame for video), as soon as the source has pixels.
       const bindTexture = (name: string, slot: UniformSlot, source: TexImageSource) => {
         if (!gl || slot.type !== gl.SAMPLER_2D) return;
         let entry = textures.get(name);
         if (!entry) {
           const texture = gl.createTexture();
           if (!texture) return;
           entry = { texture, unit: textures.size, source: null, ready: false };
           textures.set(name, entry);
         }
         gl.activeTexture(gl.TEXTURE0 + entry.unit);
         gl.bindTexture(gl.TEXTURE_2D, entry.texture);
         const hasPixels =
           typeof HTMLImageElement !== "undefined" && source instanceof HTMLImageElement
             ? source.complete && source.naturalWidth > 0
             : typeof HTMLVideoElement !== "undefined" && source instanceof HTMLVideoElement
               ? source.readyState >= 2
               : true;
         const isVideo = typeof HTMLVideoElement !== "undefined" && source instanceof HTMLVideoElement;
         if (hasPixels && (entry.source !== source || !entry.ready || isVideo)) {
           gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, true);
           gl.pixelStorei(gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL, true);
           gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, source);
           gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
           gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
           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);
           entry.source = source;
           entry.ready = true;
         }
         gl.uniform1i(slot.location, entry.unit);
       };
   
       const still = () => reducedMotion.matches;
       const shouldRun = () => !lost && program !== null && inView && pageVisible && !latest.current.paused && !still();
   
       const frame = (now: number) => {
         raf = 0;
         if (!shouldRun()) return settle();
         const dt = lastFrame ? Math.min((now - lastFrame) / 1000, 0.1) : 0;
         lastFrame = now;
         clock += dt * (latest.current.speed ?? 1);
         const ease = 1 - Math.exp(-dt * 6);
         mouse[0] += (mouseTarget[0] - mouse[0]) * ease;
         mouse[1] += (mouseTarget[1] - mouse[1]) * ease;
         pointer += (pointerTarget - pointer) * ease;
         draw(clock);
         time.current = clock;
         report("running");
         raf = requestAnimationFrame(frame);
       };
   
       // Not animating: keep one up-to-date frame on screen.
       const settle = () => {
         lastFrame = 0;
         if (lost || !program) return;
         time.current = still() ? (latest.current.staticTime ?? 6) : clock;
         draw(time.current);
         report("static");
       };
   
       const update = () => {
         if (shouldRun()) {
           if (!raf) raf = requestAnimationFrame(frame);
           return;
         }
         if (raf) cancelAnimationFrame(raf);
         raf = 0;
         settle();
       };
   
       const intersection = new IntersectionObserver(
         ([entry]) => {
           inView = entry.isIntersecting;
           update();
         },
         { rootMargin: "120px" },
       );
       const resizeObserver = new ResizeObserver(() => {
         needsResize = true;
         if (!raf) settle();
       });
       const onVisibility = () => {
         pageVisible = document.visibilityState === "visible";
         update();
       };
       const onPointerMove = (event: PointerEvent) => {
         const rect = host.getBoundingClientRect();
         const x = (event.clientX - rect.left) / rect.width;
         const y = 1 - (event.clientY - rect.top) / rect.height;
         const inside = x >= 0 && x <= 1 && y >= 0 && y <= 1;
         if (inside) {
           mouseTarget[0] = x;
           mouseTarget[1] = y;
         }
         pointerTarget = inside ? 1 : 0;
       };
       const onPointerLeave = () => {
         pointerTarget = 0;
       };
       const onContextLost = (event: Event) => {
         event.preventDefault();
         lost = true;
         if (raf) cancelAnimationFrame(raf);
         raf = 0;
         report("fallback");
       };
       const onContextRestored = () => {
         lost = false;
         if (build()) update();
         else report("fallback");
       };
       const trackPointer = latest.current.pointer === true;
   
       // Start on the next frame: keeps setup out of the effect body and off the hydration task.
       const start = requestAnimationFrame(() => {
         if (!build()) return report("fallback");
         canvas.addEventListener("webglcontextlost", onContextLost);
         canvas.addEventListener("webglcontextrestored", onContextRestored);
         document.addEventListener("visibilitychange", onVisibility);
         reducedMotion.addEventListener("change", update);
         if (trackPointer) {
           window.addEventListener("pointermove", onPointerMove, { passive: true });
           document.documentElement.addEventListener("pointerleave", onPointerLeave);
         }
         intersection.observe(host);
         resizeObserver.observe(host);
         wake.current = update;
       });
   
       return () => {
         cancelAnimationFrame(start);
         if (raf) cancelAnimationFrame(raf);
         wake.current = () => {};
         intersection.disconnect();
         resizeObserver.disconnect();
         canvas.removeEventListener("webglcontextlost", onContextLost);
         canvas.removeEventListener("webglcontextrestored", onContextRestored);
         document.removeEventListener("visibilitychange", onVisibility);
         reducedMotion.removeEventListener("change", update);
         window.removeEventListener("pointermove", onPointerMove);
         document.documentElement.removeEventListener("pointerleave", onPointerLeave);
         if (gl) {
           textures.forEach((entry) => gl?.deleteTexture(entry.texture));
           if (program) gl.deleteProgram(program);
           gl.getExtension("WEBGL_lose_context")?.loseContext();
         }
         canvas.remove();
       };
     }, [fragmentShader]);
   
     /** `time` holds the shader clock (seconds, as passed to u_time), e.g. to timestamp clicks. */
     return { ref, status, time };
   }

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3. Copy the source

   components/ui/dithered-waves/dithered-waves.tsx

   "use client";
   
   import type { ComponentProps, ReactNode } from "react";
   import { cn } from "@/lib/utils";
   import { hexToVec3 } from "@/lib/color";
   import { GLSL_BAYER, GLSL_NOISE } from "@/lib/webgl/noise.glsl";
   import { useShaderCanvas } from "@/lib/webgl/use-shader-canvas";
   
   export interface DitheredWavesProps extends Omit<ComponentProps<"div">, "children"> {
     /** Content rendered above the waves. */
     children?: ReactNode;
     /** Size of one dither pixel in CSS pixels, 2–8. @default 3 */
     pixelSize?: number;
     /** Ink color. @default "#09090B" */
     color?: string;
     /** Paper color. @default "#FFFFFF" */
     backgroundColor?: string;
     /** Wave density from 0 to 1.5. @default 1 */
     intensity?: number;
     /** Wave speed multiplier. @default 1 */
     speed?: number;
     /** Freeze on the current frame. @default false */
     paused?: boolean;
   }
   
   const FRAGMENT = /* glsl */ `${GLSL_NOISE}${GLSL_BAYER}
   uniform float u_pixel; uniform vec3 u_ink; uniform vec3 u_paper; uniform float u_intensity;
   void main() {
     vec2 cell = floor(gl_FragCoord.xy / u_pixel);
     vec2 uv = cell * u_pixel / u_resolution;
     vec2 p = vec2(uv.x * u_resolution.x / u_resolution.y, uv.y);
     float t = u_time * 0.5;
     float w = sin(p.y * 9.0 + sin(p.x * 2.6 + t) * 1.6 + fbm(p * 1.5 + t * 0.2, 3) * 2.0 - t * 0.6) * 0.5 + 0.5;
     float v = w * smoothstep(1.05, 0.0, uv.y) * u_intensity;
     float ink = step(bayer8(cell) + 0.001, v);
     fragColor = vec4(mix(u_paper, u_ink, ink), 1.0);
   }`;
   
   export function DitheredWaves({
     children,
     pixelSize = 3,
     color = "#09090B",
     backgroundColor = "#FFFFFF",
     intensity = 1,
     speed = 1,
     paused = false,
     className,
     style,
     ...props
   }: DitheredWavesProps) {
     // One canvas pixel per CSS pixel keeps the dither grid crisp and pixelSize exact.
     const { ref } = useShaderCanvas<HTMLDivElement>({
       fragmentShader: FRAGMENT,
       maxDpr: 1,
       speed,
       paused,
       uniforms: {
         u_pixel: Math.min(8, Math.max(2, Math.round(pixelSize))),
         u_ink: hexToVec3(color),
         u_paper: hexToVec3(backgroundColor),
         u_intensity: intensity,
       },
     });
     return (
       <div
         className={cn("relative isolate overflow-hidden", className)}
         style={{
           background: `radial-gradient(color-mix(in oklab, ${color} 35%, transparent) 1px, transparent 1.5px) 0 0 / ${pixelSize * 2}px ${pixelSize * 2}px, linear-gradient(to top, color-mix(in oklab, ${color} 18%, ${backgroundColor}), ${backgroundColor} 70%)`,
           ...style,
         }}
         {...props}
       >
         <div ref={ref} aria-hidden="true" className="absolute inset-0 -z-10 [&>canvas]:[image-rendering:pixelated]" />
         {children}
       </div>
     );
   }

   Show all 77 lines

Usage#

import { DitheredWaves } from "@/components/ui/dithered-waves/dithered-waves";

<DitheredWaves className="h-80" pixelSize={3} />

API reference#

Accessibility#

• The canvas is decorative (aria-hidden); children render above it as normal content.
• With reduced motion the shader draws a single still frame. Without WebGL2, or on software rendering with no GPU, a CSS fallback in the same colors is shown.