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

• 30 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.
  • 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.
• 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.

Controls

• Design / Output tabs at the top of the panel: Design holds the paper, layers and pattern parameters; 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/.

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.