Clyune Component GalleryL-System · How it works & code
Start with string "F" and replace each F with a longer sequence of instructions, repeat several times; then have the 'turtle' draw: F move forward and draw a line...
Runtime logic
Visiting `/generative/lsystem`, DemoHost lazy-loads `demos/kits/kit-generative.js` (registry `mod: 'kit-generative'`) and calls `mount(host, { variant: 'lsystem' })`. mount resolves the variant to family `lsystem`; `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.lineTo() — Adds a straight line to a point; ctx.stroke() — Strokes the current path; ctx.arcTo() — Adds an arc using tangent lines; ctx.closePath() — Closes the current sub-path; ctx.fill() — Fills 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.lsystem (L309-L321)
Code walkthrough
L309-321: Calls the factory `gFam()` to produce the full definition (spec + doc + build) from the options below. L309-309: Title shown in the info and control panels: “L-System Plant”. L309-309: Range/default of the size slider: Line width. L309-309: Range/default of the count slider: Iteration Count. L310-310: Extra demo-specific slider/toggle: Turn Angle. L310-310: Default main colour. L310-310: Help text of the count parameter. L310-310: Preset buttons: name → parameter overrides (5). L311-311: Body of the “Notes” section. L311-311: Main formula of the “Formula” section. L311-311: Second formula line. L312-321: Per-frame draw function: draws with Canvas 2D `beginPath`, `moveTo`, `lineTo`, `stroke`; math via `Math.pow`, `Math.min`, `Math.floor`, `Math.sin`, `Math.cos`, `Math.round`; returns readouts `mode`, `n`, `cell` to the info panel.
Principles
Rule: F → FF+[+F−F−F]−[−F+F+F] + / −: Rotating ± angles,[ ]: Staples / Out! L-System: Start with the string "F" and replace each F by a series of longer commands, repeated several times; then let the turtle paint: F go forward, + / - Turn, [ ] remember / Back to the fork. Plants grow slowly from their roots and the wind shakes the branches. 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。