PlotterGraph

Generative line art with a live-adjustable GUI, built as a single Processing sketch. Designed for pen plotters: everything exports as clean, millimetre-accurate SVG.

Features

• 35 patterns — flow field, wave lines, spirograph, noise rings, Lissajous, contour map, Truchet tiles, hatch shading, strange attractor, superformula, nested polygons, spiral, moire circles, circle packing, harmonograph, Hilbert curve, sunburst, maze, L-system, guilloche, Maurer rose, phyllotaxis, subdivision, warped grid, fractal tree, Voronoi, image, hex Truchet, Penrose, hex maze, route, data lines, SVG import, audio, text.
  • Maze — recursive-backtracker maze drawn as walls or as its centre-line path (same seed on two layers = walls + solution-style path in a second pen). Wall segments are merged into long strokes to minimise pen lifts.
  • L-system — Koch snowflake, dragon curve, Gosper curve, Sierpinski arrowhead and a branching plant, with angle tweak, jitter and smoothing.
  • Guilloche — banknote-style rosettes: interleaved lines oscillating between two lobed envelopes.
  • Maurer rose — straight chords stepping around a rose curve; optional rose outline and extra copies with a shifted step.
  • Phyllotaxis — golden-angle sunflower layout drawn as circles, radial dashes or the Fibonacci spiral families.
  • Subdivision — recursive rectangle splits, cells filled with serpentine (single-stroke) hatching, cross-hatching or concentric squares.
  • Warped grid — op-art line grid bent by lens bulges (or pinches) and optional noise.
  • Fractal tree — recursive branches with angle/length randomness and bend; each branch continues the parent stroke.
  • Voronoi — Lloyd-relaxed cells with shared borders drawn once, plus optional smoothed inset rings ("pebbles").
  • Image — turn a photo (PNG/JPG/GIF) into a single-stroke TSP line, stipple dots, tone-based cross-hatching, a wiggling spiral or squiggle lines. Contrast, brightness and invert controls; without a photo a built-in demo picture is used.
  • Hex Truchet — hexagonal Truchet tiles with arcs, mixed straight/arc tiles or a random mix; strokes are joined across tiles.
  • Penrose — P3 rhomb tiling by Robinson-triangle subdivision, drawn as rhombs, as matching arcs (closed loops) or both.
  • Hex maze — recursive-backtracker maze on a hexagon grid, as walls or centre-line path, with optional loops.
  • Route — GPX tracks, GeoJSON lines/polygons or OpenStreetMap streets, with smoothing, parallel copies and a rectangle or circle frame (a "city map" poster).
  • Data lines — numbers from a CSV or JSON file as stacked ridgelines ("Unknown Pleasures"), rings or a spiral.
  • SVG import — paths, shapes and transforms from an SVG file, outlined and/or filled with (cross-)hatching.
  • Audio — a WAV / AIFF file as waveform rows, a waveform spiral or a spectrum ridgeline.
  • Text — single-line Hershey fonts (sans, serif, script): each letter is one pen stroke, not an outline.
• External sources (Sources tab) — photos, data, maps, terrain, weather, SVG, audio and text from files, web addresses or a watched folder; text-to-design; AI-generated designs; a command-line mode. See External sources.
• Field sources — Flow field, Wave lines, Contour map and Hatch shading can follow a photo or a grid (CSV matrix, elevation data, heightmap) instead of noise.
• Up to 4 pen layers — each with its own pattern, seed, parameters, pen colour, pen width, scale/rotate/offset transform and mask. Combine patterns, or plot each layer with a different pen.
• Live preview — drag sliders, pick paper size (A5/A4/A3/Square, portrait or landscape), and see the result update immediately.
• Undo / redo — every parameter change (a whole slider drag counts as one step), up to 200 steps.
• Parameter locks — right-click a pattern parameter or the seed to lock it; Randomize, New seed and batch export leave locked values alone.
• Masks — keep a layer only inside or outside a shape: typed text (use | for a new line) in any font installed on your system, or a loaded PNG/JPG/GIF/SVG silhouette, with threshold and invert.
• Plot time estimate — pen-down distance, pen-up travel and number of pen lifts per layer, turned into a plot time from your plotter's speeds.
• Path clean-up — simplification (Ramer-Douglas-Peucker), joining paths whose ends nearly touch, dropping tiny fragments and duplicate paths, and nearest-neighbour travel optimisation. The preview, statistics and export all use the cleaned-up paths.
• Registration marks and pen test swatches — optional corner crosshairs drawn by every pen (to line the paper up after a pen change) and a small test patch per pen, plotted first, in the bottom margin.
• Export — SVG (real paper size in millimetres, one Inkscape layer per pen), G-code (GRBL-style, Z-axis or servo pen lift) or HPGL; optionally one file per pen.
• Batch export — write a series of variations (seed +1, +2, …) in one go into exports/batch_<timestamp>/.
• Presets — save and load the full setup (paper, output settings, mask, all 4 layers including locks) as JSON. A handful of example presets are included in GenerativeLineArt/presets.

Running it

Open GenerativeLineArt/GenerativeLineArt.pde in the Processing IDE (4.x) and press Run. No extra libraries are required. The sketch is split over several tabs (Sources, DataPatterns, SvgImport, Audio, TextFont, AiDesign, Cli), which the IDE opens together.

Controls

• Design / Sources / Output tabs at the top of the panel: Design holds the paper, layers and pattern parameters; Sources loads external data (see below); Output holds the plotter speeds and time estimate, path clean-up, registration marks / pen test, mask source, export format and batch export.
• Sliders / dials in the left panel adjust the current layer's parameters live. Mouse wheel over a slider = fine adjustment; elsewhere in the panel it scrolls.
• Right-click a pattern parameter or the seed to lock / unlock it (a padlock appears next to its name).
• Layer tabs (1–4) switch which pen layer you're editing.
• Pattern dropdown picks the pattern for the current layer; Left/Right arrow keys cycle through patterns.
• New seed / Randomize / Reset buttons (or N/Space, R) regenerate the current layer.
• Undo / Redo buttons, or Ctrl+Z and Ctrl+Y / Ctrl+Shift+Z (Cmd on macOS).
• Mask (Design tab, per layer): Off / Inside / Outside. Pick the text or image on the Output tab.
• Font (Output tab, text mask): click to open a list of every installed font. Type to filter it (e.g. bold), scroll with the mouse wheel or Up/Down, then click a font or press Enter. The font is saved in presets; if a preset's font isn't installed, the current font stays.
• Export ... (or S) opens a save dialog in the chosen format; a quick-save also writes into GenerativeLineArt/exports/.
• Save preset... / Load preset... (or P, L) store/restore the whole setup as JSON in GenerativeLineArt/presets/.
• Text fields (mask text, URL, place, prompt): click to type, Ctrl+V / Cmd+V pastes, Enter runs the button next to the field.

External sources

Everything on the Sources tab brings outside data into a design. When a source is loaded, a layer switches to the pattern that draws it (unless an enabled layer already does; if the current layer already shows another source, the next free layer is used, so sources add up on separate pens). Presets remember the sources: downloads are kept in GenerativeLineArt/cache/, so a preset keeps giving the same design, also offline.

Source	How	Drawn by
Photo (PNG/JPG/GIF)	Photo..., URL, watch folder	Image pattern, or as a field
CSV / JSON numbers	CSV / JSON..., URL	Data lines
GPX / GeoJSON	GPX / GeoJSON..., URL	Route
OpenStreetMap streets, water, buildings	Fetch streets (place + radius)	Route
Terrain (elevation)	Fetch terrain (place + zoom)	Contour map (field = Grid)
Weather (hourly temperature, last 92 days)	Fetch weather (place)	Data lines, one row per day
Grid: CSV matrix, ESRI .asc, grey-scale heightmap	Grid / DEM...	field = Grid
SVG	SVG..., URL	SVG import
Audio (WAV/AIFF/AU)	Audio..., URL	Audio
Text (.txt)	URL, watch folder	Text
Preset (.json with layers)	URL, watch folder	—

• Location — type a place name (looked up with OpenStreetMap Nominatim) or lat, lon, then Find. Radius sets the street area, Terrain zoom the terrain detail (higher = smaller area).
• CSV — every numeric column becomes a series; text columns and constant columns are skipped, the header gives the names. Comma, semicolon (with decimal commas, as Dutch Excel writes them), tab and | are recognised. When a date column runs newest-first, the rows are put in date order. JSON — every array of numbers, or array of objects with numeric fields, becomes a series.
• Data lines — Row length cuts a long series into rows (0 = automatic; hourly weather gives rows of 24). Scale per row normalises each row on its own.
• Field (Design tab, for Flow field, Wave lines, Contour map, Hatch shading) — Noise is the classic behaviour; Photo follows the darkness of the loaded photo (or a demo); Grid follows the loaded grid / terrain. The field covers the drawing area.
• Web address — paste a link to any of the file types above and press Fetch URL; the type comes from the link or the content.
• Watch folder — choose a folder and tick Watch: every new file dropped into it is loaded, and with Auto-export the result is written to exports/<file name>_<time>.<ext>. Handy with OneDrive / SharePoint sync or Power Automate.
• Text → design — Seed from text turns a name or phrase into the layer's seed; Design from text also picks the pattern and its parameters. The same text always gives the same design (e.g. one design per customer or guest).
• AI design — describe a design ("calm ocean waves in two blues, A3 landscape") and Claude returns a preset, which is applied (Undo takes it back). This needs an Anthropic API key in the ANTHROPIC_API_KEY environment variable, set before starting Processing (optionally ANTHROPIC_BASE_URL for a gateway). The prompt, the list of patterns and the names of loaded sources are sent to the Anthropic API; nothing else.

Map data © OpenStreetMap contributors (ODbL); credit it when you publish a plot. Terrain: Terrarium elevation tiles (AWS Open Data). Weather: Open-Meteo. These services are free for light use; please don't hammer them.

Command line

The sketch can run without the GUI, for scripts, scheduled tasks or flows. Arguments go after --run (or straight to an exported application):

Processing cli --sketch=GenerativeLineArt --run --preset presets/wave_lines_a3.json --out exports/waves.svg
Processing cli --sketch=GenerativeLineArt --run --input route.gpx --text "Sunday ride" --layer 2 --format gcode --out ride.gcode
Processing cli --sketch=GenerativeLineArt --run --location "Utrecht" --streets major --radius 2000 --out utrecht.svg
Processing cli --sketch=GenerativeLineArt --run --design-text "Anna & Tom" --batch 10
Processing cli --sketch=GenerativeLineArt --run --watch C:\Plots\Inbox

Options: --preset, --input <file|url> (repeatable), --grid, --layer, --location, --streets [all|major|water|buildings], --radius, --terrain [zoom], --weather, --text, --seed, --seed-text, --design-text, --prompt, --paper, --landscape / --portrait, --format svg|gcode|hpgl, --out, --batch <n>, --watch <folder>, --help. Relative paths are relative to the current directory. Without --watch the window stays hidden and the sketch quits after exporting, with exit code 1 when something failed. On a Linux server without a display, run it under xvfb-run.

Plotting

Exported SVGs use millimetre units matching the chosen paper size, with each pen layer as a separate <g> (Inkscape layer) so multi-pen plots can be sent one layer at a time to software like Inkscape + the AxiDraw extension, vpype, or similar plotter tools.

G-code is written for GRBL-style pen plotters: millimetres, absolute coordinates, G1 moves at the pen-down / travel speeds set on the Output tab, and the pen lifted either with the Z axis (G0 Z<up> / G1 Z<down>) or a servo (M3 S<up> / M3 S<down>). After every lift there is a G4 P<seconds> dwell (GRBL takes seconds; Marlin reads P as milliseconds, so set the lift time to 0 there). By default the origin is the bottom-left corner with Y pointing up; untick Origin bottom-left for a top-left origin. With several layers in one file the plotter returns to the origin and pauses (M0) for each pen change.

HPGL uses 40 plotter units per mm with the origin bottom-left; layer n is drawn with pen n (SP1–SP4), so a pen carousel can plot all layers in one go.

The time estimate is pen-down distance ÷ pen-down speed + travel ÷ travel speed + 2 × pen-lift time per stroke. Acceleration is ignored, so treat it as a rough guide.

License

CC0 1.0 Universal — see LICENSE. The Hershey font data in GenerativeLineArt/data/ comes with its own notice (HERSHEY_FONTS_NOTICE.txt).