Export STEP - OpenGeometry

OpenGeometry.exportStep(options) writes a STEP file. It returns a promise of { text, report }.

Option	Default	Meaning
`nodes`	required	Bodies, assemblies, or `ogId` strings
`unit`	`'millimetre'`	`'millimetre'` or `'metre'`
`upAxis`	`'Z'`	`'Z'` or `'Y'`. The model is Y up; the file is Z up by default
`name`	none	The product name in the file
`timestamp`	the current time	The time in the file header, for files that must not change

import {
  OpenGeometry,
  Solid,
  SystemAssembly,
  OG_PRIMITIVE_CUBOID,
  OG_PRIMITIVE_CYLINDER,
} from 'opengeometry';

await OpenGeometry.create(
  { wasmURL: '/opengeometry_bg.wasm' },
  { workerURL: '/tessellation-worker.js' },
);

const stool = new SystemAssembly({ ogId: 'stool' });
new Solid(
  OG_PRIMITIVE_CYLINDER,
  { radius: 0.18, height: 0.04 },
  { parent: stool, plane: { origin: [0, 0.45, 0] } },
);
new Solid(OG_PRIMITIVE_CUBOID, { width: 0.04, height: 0.45, depth: 0.04 }, { parent: stool });

const { text, report } = await OpenGeometry.exportStep({
  nodes: [stool],
  unit: 'millimetre',
  upAxis: 'Z',
  name: 'Stool',
  timestamp: '2026-01-01T00:00:00',
});
console.log(report.products, report.solids, text.startsWith('ISO-10303-21;'));

Save the file in a browser

import { OpenGeometry, Solid, OG_PRIMITIVE_CUBOID } from 'opengeometry';

await OpenGeometry.create(
  { wasmURL: '/opengeometry_bg.wasm' },
  { workerURL: '/tessellation-worker.js' },
);

const box = new Solid(OG_PRIMITIVE_CUBOID, { width: 1, height: 1, depth: 1 });
const { text } = await OpenGeometry.exportStep({ nodes: [box] });
const link = document.createElement('a');
link.href = URL.createObjectURL(new Blob([text], { type: 'model/step' }));
link.download = 'box.step';
link.click();

The report

report counts what was written: products, solids, faces, edges, cavityShells, entities and bytes. It also gives the exchangeErrorBound and the geometricTolerance, and one entry per body in bodies. skipped lists the nodes that were not written, with a reason.

Rules

A wire or a sheet cannot be exported on its own. It throws InvalidOperand.
A selection with no solid in it throws EmptyResult.
Planes, cylinders, cones, spheres and tori are written as exact STEP surfaces. report.fittedCurves counts the curves that had to be fitted.

Last modified on November 10, 2026