Clyune Component GalleryBlack-hole Accretion · How it works & code
Particles form a flat accretion disk rotating around the center, spinning faster and hotter closer in (Keplerian motion), with a pure black circular event horizon; the pointer controls the disk...
Runtime logic
Visiting `/particles-fx/blackhole`, DemoHost lazy-loads `demos/kits/kit-particles.js` (registry `mod: 'kit-particles'`) and calls `mount(host, { variant: 'blackhole' })`. mount resolves the variant to family `blackhole`; `withControls` builds the control panel (6 presets + sliders). `createCanvasStage` creates the `<canvas>` (HiDPI ≤ 2×, ResizeObserver) and the info panel. The family’s `build(S)` initialises state and returns the per-frame callback. Every `requestAnimationFrame`: read controls, advance a speed-scaled clock (dt ≤ 50 ms), run the frame callback; returned readouts go to the info panel. Changing parameters: colour/speed/size apply live; structural ones remount; leaving the page cancels rAF, removes listeners and frees resources.
Environment
Canvas 2D: 2D canvas drawing; requestAnimationFrame: Display-synced animation loop; ResizeObserver: Canvas follows container size; Pointer Events: Unified mouse/touch/pen events; devicePixelRatio: Crisp HiDPI rendering (capped at 2×) · react 18.3.1, react-router-dom 6.30.6, vite 5.4.21
Dependencies
react 18.3.1
Imported APIs
withControls — Wraps the demo in the shared control panel (presets, sliders, reset); hot-updates or remounts on change; paramsFromSpec — Turns the spec (colour/speed/size/count/extras) into control-panel parameter definitions; createCanvasStage — Shared Canvas 2D stage: canvas + info panel, HiDPI, one rAF loop, pointer state, idle auto-pointer; hueOf — Hue of a colour (0–360°); clamp — Clamps a value to a range; TAU — Constant 2π; fmt — Number formatting (fixed decimals); F — Formula block HTML; S.clear — Clears with the background colour (translucent = trails); S.onFrame — Registers a per-frame callback; its return value feeds the info panel; ctx.beginPath() — Starts a new path; ctx.arc() — Adds a circular arc (center, radius, start/end angle); ctx.fill() — Fills the current path; ctx.stroke() — Strokes the current path; ctx.moveTo() — Moves the pen without drawing; ctx.arcTo() — Adds an arc using tangent lines; ctx.closePath() — Closes the current sub-path; ctx.fillRect() — Fills a rectangle; ctx.save() — Saves the drawing state (transform, styles, clip); ctx.rect() — Adds a rectangle to the path; ctx.clip() — Turns the current path into the clipping region; ctx.restore() — Restores the saved drawing state
Source code
frontend/src/demos/kits/kit-particles.js: FAM.blackhole (L363-L374)
Code walkthrough
L363-374: Calls the factory `pFam()` to produce the full definition (spec + doc + build) from the options below. L363-363: Title shown in the info and control panels: “Accretion disk”. L363-363: Range/default of the size slider: Particle Size. L363-363: Range/default of the count slider: Particle count. L364-364: Extra demo-specific slider/toggle: Schwarzschild radius. L364-364: Default main colour. L364-364: Preset buttons: name → parameter overrides (4). L365-365: Body of the “Notes” section. L365-365: Main formula of the “Formula” section. L365-365: Second formula line. L366-374: Per-frame draw function: draws with Canvas 2D `beginPath`, `arc`, `fill`, `stroke`; math via `Math.min`, `Math.pow`, `Math.cos`, `Math.sin`.
Principles
ω (r) r^ (-1.5) (Kepler) Temperature / Brightness, twilight (visibility) / r)^0.75 Black Hole: The more the particles rotate around the flat suction centre, the faster they move inside, 134. The hotter the more bright (Kepler movement), the more the center of the event vision is a pure black circle; the pointer tilts the plate. The location of each particle here is numbered i Random Feeds + Time t + 指针位置」直接算出来，所以拖动滑条会立刻生效。