Railway Track — draw.io Generation

Generate top-down schematic railway track diagrams as .drawio XML files with LEGO/BRIO-style building pieces that snap together via turtle graphics.

See README.md in this folder for full component specifications, dimensions, and derived constants.

Engine Location

.cursor/skills/railway-drawio/_railway-engine.js

Building Pieces

Key Geometry

• L = 200px — straight piece length
• R = 283px — bend radius (L/sin 45°), makes bend dx = L
• GAP = 166px — track-to-track offset from turnout S-curve
• R_WIDE = 449px — wide bend radius (R + GAP), for outer ovals
• 4 bends = 180° half-circle; 4 wide bends = wider half-circle matching GAP

Turtle Graphics

Each piece's exit defines the next piece's entry. No manual coordinate math.

const r = require('./_railway-engine');
r.reset();
const t = r.track(x, y, heading);  // heading in radians (0 = right)
t.straight().bendRight().straight();
r.writeXml('output.drawio');

Turnout branches receive a new TrackBuilder in the callback:

t.turnoutLeft(branch => {
  branch.straight().wideBendRight().wideBendRight()
    .straight().wideBendRight().wideBendRight().straight();
});

Examples

• example-race.js — double-oval race track with inner/outer ovals connected by a turnout and merger
• example-race.drawio — generated output (open in draw.io)

Usage Pattern

1. Create a generator script in this folder (or require the engine from elsewhere)
2. Call r.reset(), build tracks with r.track(), call r.writeXml(path)
3. Open the .drawio file in draw.io to view