Building masses as IFC

Formats every number this file writes.

text = v.toFixed(d) with trailing zeros removed; d = 9 unless stated

Rounded to 9 decimal places by default; a value below half of the last place, or one that is not finite, is written as 0.

const R = (v, d = 9) => { if (!Number.isFinite(v)) return '0.'; let s = (Math.abs(v) < 0.5 * 10 ** -d ? 0 : v).toFixed(d).replace(/(\.\d*?)0+$/, '$1'); if (!s.includes('.')) s += '.'; return s === '-0.' ? '0.' : s; };

Meters in a US survey foot, shared with the project IFC export.

1200 ÷ 3937

Formed as the defining fraction by one division, so it is the nearest 64-bit number to the exact value.

export const FT_US_M = 1200 / 3937;   // metres in a US survey foot

Writes an angle as degrees, minutes, seconds and millionths of a second.

Whole degrees, minutes and seconds by Math.floor; the rest rounded to a millionth of an arc second, the resolution of the IFC compound angle.

const angle = (deg) => {   // IfcCompoundPlaneAngleMeasure: degrees, minutes, seconds, millionths of a second, all with the sign
  const sg = deg < 0 ? -1 : 1, a = Math.abs(deg), d = Math.floor(a), m = Math.floor((a - d) * 60), sc = ((a - d) * 60 - m) * 60, s = Math.floor(sc), u = Math.round((sc - s) * 1e6);
  return '(' + [sg * d, sg * m, sg * s, sg * u].join(',') + ')';
};

The signed area of a mass outline; its sign sets the direction the outline is written in.

A = Σ (x_i·y_j − x_j·y_i) ÷ 2

The shoelace sum on absolute project coordinates, with no shift to a local origin, so large coordinates cost digits in the area.

const signedArea = (P) => { let a = 0; for (let i = 0; i < P.length; i++) { const p = P[i], q = P[(i + 1) % P.length]; a += p.x * q.y - q.x * p.y; } return a / 2; };

The origin footprints are written from: the middle of the masses rounded to 10 units, at the lowest ground floor level.

origin = round((min + max) ÷ 20) × 10

The plan origin is a whole multiple of 10. The z origin is the lowest ground floor level as it is, not rounded.

export function defaultOrigin(masses) {
  let x0 = Infinity, y0 = Infinity, x1 = -Infinity, y1 = -Infinity, z = Infinity;
  for (const m of masses) { for (const p of m.pts) { x0 = Math.min(x0, p.x); y0 = Math.min(y0, p.y); x1 = Math.max(x1, p.x); y1 = Math.max(y1, p.y); } z = Math.min(z, m.z0); }
  return masses.length ? { x: Math.round((x0 + x1) / 20) * 10, y: Math.round((y0 + y1) / 20) * 10, z: Number.isFinite(z) ? z : 0 } : { x: 0, y: 0, z: 0 };
}

The height, footprint area and gross floor area written in the mass's properties.

H = floors × floor height; footprint (m²) = A × um²; gross = A × floors × um²

um is 1, 0.3048 or 1200 ÷ 3937. Storey elevations are z₀ + k × floor height from the whole-number storey index, not a running sum. All are written with 9 decimals.

const um = unit === 'm' ? 1 : unit === 'ft' ? 0.3048 : FT_US_M, area = (a) => a * um * um;   // sq project units → m²