6. Vector Formats, Sources & Workflows¶

A pen plotter does not render pixel grids—it drives mathematical vector paths using physical pens. Whether you create artwork with code (Python, Processing), 3D applications like Blender, vector editors like Inkscape, or CAD systems, here are the best practices for generating clean data for LINTO.

1. Custom Scripts (Generating Clean SVGs)¶

For generative art (Plotter Art) created via Python, JavaScript, or Processing, SVG is the ideal format. Following four simple guidelines ensures that your dimensions and pen assignments import 1:1 without manual tweaking:

1. Keep Millimeters (mm) and viewBox in Sync: Set width and height explicitly in mm and reuse the exact numbers in the viewBox. Then 1.0 in your script's coordinate space corresponds to exactly 1 millimeter on paper:

   <svg xmlns="http://www.w3.org/2000/svg"
        width="420mm" height="297mm"
        viewBox="0 0 420 297">
     <!-- 1 unit = 1 mm on a DIN A3 landscape sheet -->
   </svg>
   

   (Without explicit units, SVG defaults to pixels at 96 DPI, where 1 px ≈ 0.2646 mm.)

2. Pen Mapping via Stroke Color (stroke): LINTO maps paths to pens 1–8 based on their stroke hex color. If your script uses the 8 default hex colors, every path will land reliably on the intended pen:

<!-- Lands automatically on Pen 1 (Black) -->
<path d="M 10,10 L 100,10 L 100,100 Z" fill="none" stroke="#000000" stroke-width="0.35" />

<!-- Lands automatically on Pen 2 (Red) -->
<circle cx="55" cy="55" r="30" fill="none" stroke="#d32f2f" stroke-width="0.35" />

1. Always Set fill="none": Pen plotters only draw stroke lines, not solid fills. Setting fill="none" ensures that what you see in your web browser or SVG preview matches what the pen will physically draw.

2. Supported SVG Elements: You can freely mix <path>, <line>, <polyline>, <polygon>, <rect>, <circle>, <ellipse>, <text> (including <tspan>), and nested <g transform="..."> groups. Curves (C, Q, A) are parsed losslessly.

3. SVG <text> Import (Single-Line Font Fallback): Standard <text> elements are automatically rendered using an integrated Hershey Simplex single-stroke vector font (supporting ASCII, German umlauts/ß, and common diacritics) with font-size, text-anchor (start, middle, end), and dx/dy offsets. LINTO still displays an informational warning on import and in the pre-flight panel reminding you that <text> was replaced by a single-line font (convert text to paths in your editor if you need the exact original typeface outlines).

2. Inkscape as a Universal Pre-Converter¶

Inkscape is the "Swiss Army knife" for plotter preparation. Virtually any third-party vector format can be inspected, cleaned, and exported as SVG:

• Vector & Print Formats: .pdf, .eps, .ps (note: PDF text fonts often import as double-line outlines), Adobe Illustrator (.ai), CorelDRAW (.cdr), Visio (.vsd/.vsdx), .wmf/.emf.
• CAD Formats: .dxf (AutoCAD R12/R14/2000+) and .hpgl/.plt.
• Single-Line Fonts (Hershey Text): Standard fonts (TrueType/OpenType) consist of closed outline contours (e.g. an "I" is drawn as a narrow rectangle). While LINTO automatically substitutes raw SVG <text> elements with its built-in Hershey Simplex single-line font, Inkscape provides additional typeface styles under Extensions → Text → Hershey Text (or Path → Object to Path if you intentionally want double-line outline lettering).
• Bitmap Vectorization (Centerline Tracing): Via Path → Trace Bitmap, Inkscape offers Centerline Tracing (Autotrace). Unlike outline tracing (which traces both sides of a black line), centerline tracing creates a single clean centerline for the pen.

3. Blender (Exporting 3D Scenes as 2D SVG)¶

Blender is well-suited for 3D generative art, architectural wireframes, and perspective line drawings with automatic Hidden Line Removal (hidden edges on the back side of meshes are cleanly omitted):

1. Freestyle SVG Exporter (Built-in Add-on):
2. Enable the Freestyle SVG Exporter under Edit → Preferences → Add-ons.
3. Check Freestyle and Freestyle SVG Export in Render Properties.
4. Press F12 to render: Blender writes a clean .svg file containing all visible camera edges.
5. Grease Pencil + Line Art Modifier (Blender 3.x / 4.x, fast):
6. Add Grease Pencil → Scene Line Art to the scene (calculates silhouettes, creases, and intersections in real time).
7. Export directly via File → Export → Grease Pencil as SVG (.svg).

4. HP-GL (.hpgl / .plt)¶

HP-GL (Hewlett-Packard Graphics Language) is an industry-standard machine control language (PU = Pen Up, PD = Pen Down, SP = Select Pen) with a fixed coordinate step of 1 unit = 0.025 mm.

• Direct Import in LINTO: Load existing .hpgl and .plt files directly via File → Import (Ctrl+I), File → Open Project (Ctrl+O), or drag-and-drop.
• Supported Commands: In addition to absolute/relative moves (PA, PR, PU, PD) and pen changes (SP1–SP8), the parser supports geometric primitives (CI circles, AA/AR arcs, EA/RA rectangles) and LB text labels (including sizing SI, direction DI/DR, slant SL, and character plot CP) via an integrated 5×7 vector font.
• Accuracy & External Converters: Curves in HP-GL files are broken into short linear segments. If you need to convert old HP-GL files outside LINTO, tools like Inkscape, vpype (with vpype-hpgl), or the classic CLI utility hp2xx (hp2xx -m svg input.hpgl -f output.svg) work well.

5. DXF (CAD Drawings)¶

DXF (Drawing Exchange Format) is the standard 2D exchange format in CAD, architecture, and CNC/laser cutting (AutoCAD, FreeCAD, QCAD, LibreCAD, Rhino, Fusion 360).

• Plotter Considerations: CAD drawings often organize geometry across layers or ACI color numbers and may contain disconnected line fragments or dimension blocks.
• Recommended Workflow: Export drawings directly as SVG from your CAD software (e.g. in QCAD or FreeCAD TechDraw) or open the .dxf in Inkscape (keep scaling factor at 1.0 for millimeters) and save as .svg for LINTO.