Carbon weave

Good for

Phone cases, sporty parts, carbon-filled filament.

Print notes

• Depth 0.4 to 1.5 mm for a 0.4 mm nozzle (as written: 0.7 mm).
• Best on walls, printed upright. On a flat top, use thin layers (0.12 mm or less).
• Fade it out over the bottom 3 mm so the first layers are flat and stick to the plate.
• Not printed yet: these notes come from the geometry. The test cube will tell us more.

The formula

The real code this page runs: give it a point (U mm across, V mm up) and it returns the height there, in mm. Push the surface out by that much and the texture is real geometry.

function carbonWeave(U: number, V: number, p = 4.0, amp = 0.7) {
  const i = Math.floor(U / p);
  const j = Math.floor(V / p);
  const s = frac(U / p);
  const t = frac(V / p);
  const over = mod(i + j, 4) < 2; // 2x2 twill: the over/under steps a cell each row
  const along = over ? s : t;
  const across = over ? t : s;
  return amp * (0.55 + 0.45 * Math.sin(Math.PI * along)) * dome(((across - 0.5) / 0.47) ** 2);
}

/** Python's floor modulo: the result has the sign of b (`-1 % 2` is 1, as in numpy). */
function mod(a: number, b: number) {
  return a - b * Math.floor(a / b);
}

/** The fractional part, 0..1. */
function frac(x: number) {
  return x - Math.floor(x);
}

/** A round bump: 1 in the middle (r2 = 0), 0 at the edge (r2 = 1). */
function dome(r2: number) {
  return Math.sqrt(clamp(1 - r2, 0, 1));
}

function clamp(x: number, lo: number, hi: number) {
  return Math.min(Math.max(x, lo), hi);
}

Printed