Shader `<mv-shader>`

Fonctionnement

Moteur WebGL2 plein cadre pour votre propre fragment shader : GLSL en ligne, shader complet collé ou mainImage() en une seule passe, tout s’exécute derrière le contenu de l’élément, avec des uniforms fournis pour le pointeur, le défilement et les tokens du thème. Il se met en pause hors écran, partage le budget de contextes WebGL de la page, garde une image fixe en mouvement réduit et se rabat sur une esquisse en tokens sans WebGL2. Sans GLSL, il dessine sa propre carte de courbes de niveau qui dérive, aux couleurs du thème.

Catégorie	Arrière-plans
Type	Web Component (`<mv-shader>`)
Statut	stable
Keywords	safe-rewrite, webgl, glsl, shader, background, runtime, contour

When to use

A custom fragment shader must run as a section background with off-screen pause and reduced motion built in
A reusable branded background should be built by subclassing with its own uniforms and GLSL
An existing GLSL effect needs to be ported without adding a WebGL library
A quiet, theme-aware contour texture is wanted behind a hero or a feature band

Avoid when

A ready-made preset already matches the look, e.g. a fluid brand gradient → use Mesh Gradient instead
Nobody on the team maintains GLSL; a CSS background is easier to own → use Aurora Background instead
More than 10 shaders are on screen at once; only 10 WebGL contexts stay live, so the extra ones keep being rebuilt

Installation

node scripts/add.mjs shader --out ./src/marvelous

Agent IA avec le serveur MCP de Marvelous UI : install_components({ slugs: ["shader"], target_dir: "<absolute path>/src/marvelous", framework: "react" }).

Fichiers copiés (dépendances comprises) : tokens/tokens.css, core/base.css, core/canvas.js, core/dom.js, core/element.js, core/i18n.js, core/motion.js, core/observe.js, core/webgl.js, components/shader/shader.js, components/shader/shader.css.

Utilisation

Balisage de référence : partez de celui-ci et personnalisez-le avec les attributs, data-* et les variables CSS :

<div style="display:grid;grid-template-columns:repeat(auto-fit,minmax(260px,1fr));width:100%;height:100%;min-height:320px">
  <mv-shader style="min-height:320px;display:grid;align-content:end;padding:1.25rem;color:var(--mv-fg)">
    <p style="margin:0;width:fit-content;padding:.6rem .85rem;border-radius:var(--mv-radius-md);background:color-mix(in oklch,var(--mv-bg) 82%,transparent);backdrop-filter:blur(6px);font:600 1.05rem/1.35 var(--mv-font-sans)">Built-in default<br><span style="font-weight:400;font-size:.85rem;color:var(--mv-fg-muted)">Contour map in your theme tokens. Hover to raise it.</span></p>
  </mv-shader>
  <mv-shader style="min-height:320px;display:grid;align-content:end;padding:1.25rem;color:var(--mv-fg)">
    <script type="x-shader/x-fragment">
      // Your GLSL ES 3.0: u_time, u_resolution, u_dpr, u_mouse, u_hover and u_palette are provided.
      void main() {
        vec3 ink = u_palette[0];
        vec3 paper = u_palette[1];
        float cell = 14.0 * u_dpr;
        vec2 f = fract(gl_FragCoord.xy / cell) - 0.5;
        vec2 c = (floor(gl_FragCoord.xy / cell) + 0.5) * cell / u_resolution.y;
        vec2 m = u_mouse * u_resolution / u_resolution.y;
        float wave = 0.5 + 0.3 * sin(c.x * 9.0 + c.y * 5.0 - u_time * 1.2) + 0.2 * sin(c.y * 13.0 - c.x * 4.0 + u_time * 0.8);
        wave += 0.6 * u_hover * exp(-dot(c - m, c - m) * 16.0);
        float calm = smoothstep(0.05, 0.55, gl_FragCoord.y / u_resolution.y);
        float r = 0.05 + 0.37 * clamp(wave, 0.0, 1.0) * calm;
        float dot_ = 1.0 - smoothstep(r - 1.0 / cell, r + 1.0 / cell, length(f));
        fragColor = vec4(mix(paper, ink, dot_ * 0.85), 1.0);
      }
    </script>
    <p style="margin:0;width:fit-content;padding:.6rem .85rem;border-radius:var(--mv-radius-md);background:color-mix(in oklch,var(--mv-bg) 82%,transparent);backdrop-filter:blur(6px);font:600 1.05rem/1.35 var(--mv-font-sans)">Your own GLSL<br><span style="font-weight:400;font-size:.85rem;color:var(--mv-fg-muted)">Inline halftone, same pause and theme handling.</span></p>
  </mv-shader>
</div>

API

Attributes

Name	Type	Default	Description
`colors`	CSS colors (3)	`var(--mv-accent), var(--mv-bg), var(--mv-fg)`	Palette of `<mv-shader>` itself, as u_palette[3] (ink, paper, text): drawn by the built-in contour map and available to inline GLSL. Tokens accepted, read again on theme change.
`speed`	number	`1`	Time multiplier.
`paused`	boolean		Freezes the animation on the current frame.
`interactive`	boolean		Follows the pointer only over the element (otherwise across the whole window).
`dpr`	number	`1.5`	Max pixel density (capped at 2).
`data-fill`	boolean		Fills the positioned parent (absolute, inset 0).

Properties

Name	Type	Description
`fragment`	string \| null	The GLSL that runs. Setting it recompiles on the next frame; null goes back to the inline script or the built-in contour map.
`static fragment / uniforms / chunks`		To build a reusable background: class MvFoo extends MvShader { static chunks = ["noise"]; static uniforms = { u_colors: { attr: "colors", type: "colors", default: "var(--mv-accent), #0ea5e9", count: 3 } }; static fragment = `void main() { … }` }. Uniform types: number, color, colors, vec2, vec3, vec4, boolean. GLSL chunks: hash (hash12, hash22), noise (snoise, fbm), color (palette, gradient3).

Events

Name	Description
`mv-error`	The GLSL failed to compile or link. detail: { message } (the compiler log). The element gets data-error and shows its fallback.

Content structure

Name	Description
`<script type="x-shader/x-fragment">`	GLSL ES 3.0: a main() body, a complete shader, or a single-pass mainImage() (iTime, iResolution, iMouse mapped; no iChannel). Provided uniforms: u_time, u_resolution, u_dpr, u_mouse, u_hover, u_scroll, u_palette. data-chunks="noise color" adds GLSL chunks.
`children`	Content placed inside the element sits above the canvas.

Accessibility

Decorative: the canvas is aria-hidden and never takes pointer events; content placed inside stays in the normal reading order. The loop stops off screen and in hidden tabs, and no context is created until the element comes near the viewport. Reduced motion (OS or <html data-motion="reduce">) and paused keep a still, representative frame. Without WebGL2, or when the GLSL does not compile, a static contour sketch in the theme tokens is shown; forced colors and print hide the canvas. Text placed over a custom shader needs its own contrast check.