Plasma `<mv-plasma>`

磁化したプラズマの WebGL 背景です。ゆっくり動くいくつかの磁極が画面をさまよい、その磁力線が細いフィラメントとして光ります。ある極から出て別の極に降りる弧は、軽い反復乱流で揺らぎます。

仕組み

磁化したプラズマの WebGL 背景です。ゆっくり動くいくつかの磁極が画面をさまよい、その磁力線が細いフィラメントとして光ります。ある極から出て別の極に降りる弧は、軽い反復乱流で揺らぎます。電流の粒が弧に沿って進み、弧は端から端まで 3 色に移り変わります。ポインターは小さな磁石を持ち、近くのフィラメントがそちらへ曲がります。テーマの背景に描かれ、ライトテーマでは紙の上のインク、ダークテーマでは光る線になります。

カテゴリー	背景
タイプ	WebGL 要素（`<mv-plasma>`）
ステータス	安定版
同時にインストールされるもの	shader
Keywords	safe-rewrite, webgl, shader, plasma, field-lines, magnetic, filaments, turbulence, interactive, hero

When to use

A science, energy, AI or developer product wants a living hero backdrop that reads as precise rather than psychedelic
A launch or event page should answer the pointer with a visible but calm effect, in light and dark themes alike
A dark section needs glowing linework in the brand colors that leaves most of the frame quiet for a headline

Avoid when

Soft, flowing brand color fills the frame with no lines at all → use Mesh Gradient instead
Long body copy sits on top; the filaments cross behind it and hurt readability beyond short headlines

インストール

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

Marvelous UI の MCP サーバーを使う AI エージェント：install_components({ slugs: ["plasma"], target_dir: "<absolute path>/src/marvelous", framework: "react" })。

コピーされるファイル（依存関係を含む）：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, components/plasma/plasma.js。

使い方

基本となるマークアップです。ここから属性、data-*、CSS 変数でカスタマイズしてください：

<mv-plasma data-fill></mv-plasma>
<div style="position:relative;display:grid;place-items:center;height:100%;min-height:320px;padding:2rem 1rem;box-sizing:border-box;text-align:center;pointer-events:none">
  <div>
    <p style="margin:0;font:700 clamp(1.6rem,4vw,2.6rem)/1.1 var(--mv-font-sans);letter-spacing:-.03em;color:var(--mv-fg);text-shadow:0 0 28px var(--mv-bg),0 0 10px var(--mv-bg)">Held by the field</p>
    <p style="margin:.6rem auto 0;max-width:26rem;color:var(--mv-fg);text-shadow:0 0 16px var(--mv-bg),0 0 6px var(--mv-bg)">Move your pointer over the arcs: they bend toward it and spark.</p>
  </div>
</div>

API

Attributes

Name	タイプ	Default	Description
`colors`	CSS colors (3)	`var(--mv-accent), color-mix(in oklch, var(--mv-accent) 30%, var(--mv-fg-muted)), a hue 75 degrees before the accent`	Colors along each arc: at the positive poles, midway, at the negative poles. Tokens accepted, read again on theme change. The default third color follows --mv-accent-h and gets lighter in a dark theme.
`scale`	number	`1`	Size of the field (0.25 to 4): larger means fewer poles, longer arcs and a broader ripple.
`turbulence`	number	`1`	Strength of the ripple on the filaments, 0 to 3 (0 = clean field lines).
`intensity`	number	`1`	Filament and glow brightness, 0 to 3.
`density`	number	`1`	Number of filaments per pole (0.3 to 3, 1 = twelve).
`speed`	number	`1`	Time multiplier.
`paused`	boolean		Freezes the field 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).

Events

Name	Description
`mv-error`	Inherited from `<mv-shader>`: the GLSL failed to compile. The element gets data-error and shows its fallback.

Content structure

Name	Description
`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 WebGL context is created until the element comes near the viewport. Reduced motion (OS or <html data-motion="reduce">) and paused keep one still frame, with no pointer response. Forced colors and print hide the canvas; without WebGL2 a static sketch in the theme tokens is shown. The frame stays mostly the page background, but filaments can cross behind text: keep a headline short or give it a halo or panel in the background color.