Clyune Component GalleryContour Lines · How it works & code
Use the noise value as the height on the map 1/n、2/n… It's like a line on a map.
Runtime logic
Visiting `/generative/contour`, DemoHost lazy-loads `demos/kits/kit-generative.js` (registry `mod: 'kit-generative'`) and calls `mount(host, { variant: 'contour' })`. mount resolves the variant to family `contour`; `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.moveTo() — Moves the pen without drawing; ctx.arcTo() — Adds an arc using tangent lines; ctx.closePath() — Closes the current sub-path; ctx.fill() — Fills the current path; ctx.stroke() — Strokes the current path; ctx.fillRect() — Fills a rectangle; ctx.arc() — Adds a circular arc (center, radius, start/end angle); ctx.drawImage() — Draws an image or offscreen canvas; 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-generative.js: FAM.contour (L419-L429)
Code walkthrough
L419-429: Calls the factory `gFam()` to produce the full definition (spec + doc + build) from the options below. L419-419: Title shown in the info and control panels: “Contour Lines”. L419-419: Range/default of the size slider: Line width. L419-419: Range/default of the count slider: number of contour lines. L420-420: Extra demo-specific slider/toggle: Noise scale. L420-420: Default main colour. L420-420: Preset buttons: name → parameter overrides (5). L421-421: Body of the “Notes” section. L421-421: Main formula of the “Formula” section. L421-421: Second formula line. L422-429: Per-frame draw function: math via `Math.exp`, `Math.min`, `Math.abs`, `Math.round`, `Math.floor`; returns readouts `cell` to the info panel.
Principles
Height h = fbm(x·s, y·s, 0.08t) + Hill (pointer) Line conditions: |fract(h · n) − 0.5| > 0.5 - width · n · 0.004 Altitude: the noise value is used as the height on the map, which is exactly equal to 1 / n, 2 / n... Starting with a line on the map. The closer the line, the steeper the slope. The altitude Starting to move slowly and the pointer rises a hill. Generative Art = a simple mathematical rule + Random number/噪声，让电脑自己「画」出图案；改变参数就是改变规则。