Radar `<mv-radar>`

How it works

WebGL radar scope drawn in the theme tokens: a beam turns clockwise from north over dashed range rings and a compass scale, echoes smeared along the arc light up as it passes and fade until the next turn, moving contacts leave a plot history and a speed vector, and grainy clutter answers near the center. The pointer carries a range ring and bearing line and locks a gate onto the contact under it. Apps can plot their own contacts, alerts included. Works in light and dark themes.

Category	Backgrounds
Type	WebGL element (`<mv-radar>`)
Status	stable
Also installs	shader
Keywords	safe-rewrite, webgl, shader, radar, sweep, scope, monitoring, hud, tech, interactive

When to use

A monitoring, security or logistics hero wants a calm scanning scope behind the headline, in light or dark themes
A status panel should plot a few real items (services, vehicles, sensors) by distance and direction, with alerts flagged
A search or discovery screen needs a sense of scanning while results load

Avoid when

Real places must be shown on a map; the scope only knows range and bearing → use World Map instead
Concentric ripples over a grid are wanted without a rotating beam → use Ripple Grid instead
The contacts are data that people must read; the canvas is decorative, so give the same data as text or a table

Install

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

AI agent with the Marvelous UI MCP server: install_components({ slugs: ["radar"], target_dir: "<absolute path>/src/marvelous", framework: "react" }).

Files copied (dependencies included): 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/radar/radar.js, components/radar/radar.css.

Usage

Canonical markup, to start from and customize with attributes, data-* and CSS variables:

<div style="display:flex;flex-wrap:wrap;min-height:320px">
  <section style="flex:1.6 1 22rem;position:relative;display:flex;align-items:center;overflow:hidden;padding:2rem 1.75rem;min-height:320px">
    <mv-radar data-fill origin="0.74 0.5"></mv-radar>
    <div style="position:relative;max-width:18rem">
      <p style="margin:0;font:700 clamp(1.6rem,4vw,2.4rem)/1.1 var(--mv-font-sans);letter-spacing:-.03em">Nothing slips past</p>
      <p style="margin:.6rem 0 1.2rem;color:var(--mv-fg-muted)">Every service, swept every six seconds. Point at a contact to lock on.</p>
      <a class="mv-button" href="#radar">Start monitoring</a>
    </div>
  </section>
  <section style="flex:1 1 14rem;position:relative;display:grid;place-items:end center;text-align:center;overflow:hidden;border-left:1px solid var(--mv-border);min-height:260px;padding:1rem">
    <mv-radar data-fill origin="0.5 0.6" scale="0.78" rings="3" blips="0" clutter="0" targets="0.35 40, 0.62 128 1.4, 0.8 250 1 alert, 0.5 312"></mv-radar>
    <div style="position:relative">
      <strong style="display:block;font-size:.95rem">Your own contacts</strong>
      <span style="font-size:.8rem;color:var(--mv-fg-muted)">targets="0.8 250 1 alert, …"</span>
    </div>
  </section>
</div>

API

Attributes

Name	Type	Default	Description
`color`	CSS color	`var(--mv-accent)`	Accent of the beam, echoes, compass marker and pointer tools (tokens accepted, read again on theme change).
`background`	CSS color	`var(--mv-bg)`	Paper color under the scope (tokens accepted).
`line-color`	CSS color	`var(--mv-fg)`	Ink of the rings, spokes and compass scale, drawn at low opacity over the paper (tokens accepted).
`alert-color`	CSS color	`var(--mv-danger)`	Color of contacts marked alert in targets (tokens accepted).
`rings`	number	`4`	Number of range rings, the rim included (1 to 12).
`blips`	number	`7`	Number of decorative contacts (0 to 12); about a third stay fixed, the others patrol. 0 keeps only targets.
`targets`	string		Your own contacts, up to 8: "range bearing [strength] [alert]" separated by commas, e.g. "0.4 30, 0.8 250 1 alert". Range 0..1 of the scope, bearing in degrees clockwise from north, strength 0 to 2 (default 1). Also a JS property (array of { range, bearing, strength, alert }).
`scale`	number	`1`	Scope size relative to the element height.
`trail`	number	`1`	Length of the beam's afterglow and how long echoes persist (0.1 to 3).
`clutter`	number	`0.5`	Grainy returns around the center, 0 to 1 (0 turns them off).
`origin`	x y	`0.5 0.5`	Scope center in 0..1 element coordinates (y pointing up), e.g. "0.7 0.5" to leave room for a headline.
`speed`	number	`1`	Time multiplier (one turn takes 6 s at 1).
`paused`	boolean		Freezes the animation on the current frame.
`interactive`	boolean		Pointer tools follow the pointer only over the element itself (otherwise across the 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
`targets`	Array<{ range, bearing, strength?, alert? }>	Reads or sets the app contacts; setting it rewrites the targets attribute. Values are clamped (range 0..1, strength 0..2) and only the first 8 are drawn.

Events

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

Content structure

Name	Description
`children`	Content placed inside the element sits above the scope.

Accessibility

Decorative: the canvas is aria-hidden and never takes pointer events, so content placed above it stays clickable and in reading order. Contacts plotted with targets are not announced: give the same data as text (a list or table) when people need it. The loop stops off screen and in hidden tabs, and no WebGL context is created until the element nears the viewport. Reduced motion (OS or <html data-motion="reduce">) and paused keep a still frame with the beam to the north-east and the contacts painted. Without WebGL2 a still CSS scope is shown; forced colors and print hide the canvas. Keep headline text in the theme foreground, which the faint scope leaves readable; the beam passes behind it at low opacity.