brepjs-bim

brepjs-bim

Experimental satellite package, published to npm. Early-stage — the API may change.

npm install brepjs-bim

A BIM (Building Information Modeling) layer for brepjs. It authors IFC4-aligned parametric building elements (walls, slabs, beams, columns, roofs, curtain walls, stairs, …), assembles them into a spatial structure (project → site → building → storey), and serializes the result to a valid IFC-SPF file — with a matching importer to read IFC back in.

Pipeline: author spec → BimModel (typed element + brepjs geometry) → spatial structure + property sets + classification → export IFC / COBie, validate, round-trip.

Scope

Parametric authoring of the common IFC4 building elements plus the data layers that make a model useful downstream (psets, classification, materials, quantities), with import, export, and validation. Geometry is produced by brepjs (OCCT); each element carries a ValidSolid (or, for curtain walls, a panel/mullion grid). Element geometry is unplaced template geometry in local coordinates — placement (origin / axisX / axisZ) is applied by the IFC layer via IfcLocalPlacement, not baked into the brepjs solid. Use placedSolids(element) to read an element's geometry already transformed to its world placement as fresh, caller-owned solids (stairs return one solid per flight) — handy for display so the on-screen scene matches the IFC export.

• Units default to mm; IFC export emits SI metres.
• Stable identity: deterministic IFC GUIDs (deriveIfcGuid) and local id counters.
• Shaped geometry: roofs build real shed/gable/hip/dome solids when pitch is set (flat slab otherwise); railings build posts + top/bottom rails with infill: 'POSTED' (a single swept panel otherwise). Shaped roofs and posted railings serialize to IFC as tessellated bodies; flat roofs and panel railings keep their parametric IfcExtrudedAreaSolid.

Status

Area	State
Elements	wall, slab, beam, column, roof, curtain wall, space, footing/pile, stair, ramp, railing, covering, proxy
Profiles	rectangular / circular / I-shape cores + extended L/T/U/Z/C, hollow, ellipse, arbitrary-with-voids
Openings	door / window / slab openings cut as boolean voids; FillsOpening / Voids* relationships
Spatial structure	project → site → building → storey aggregation; placeIn to assign elements to a storey
Property sets	IFC pset templates + measure types; quantity sets for takeoff
Data layers	materials (layer/profile/simple sets), classification refs, surface styles, zones/systems
IFC export	toIfc → IFC-SPF (Uint8Array); IFC2X3 / IFC4 schema selection; owner history
IFC import	fromIfc / SpfReader → ImportedModel (elements, geometry, psets, materials, spatial tree)
Validation	referential integrity, schema check, geometry validity, IFC round-trip report
Interop	COBie 2.4 export (CSV/JSON), IDS 1.0 checking, BCF 3.0 read/write

Independent validation

The exported IFC is validated by IfcOpenShell (a separate implementation from the web-ifc parser used internally), not just self-checked. The committed sample (examples/sample-building.ifc) passes IfcOpenShell's EXPRESS schema + where-rule validator and generates geometry for every product. See VALIDATION.md to reproduce, and examples/sampleBuilding.mjs for the model it validates.

Not yet: the official buildingSMART Validation Service and desktop-tool interop (Revit / ArchiCAD / Solibri) are unverified. This is an early-stage (0.1.x) experimental package and the API will change.

Usage

Author a small model and export IFC:

import { BimModel, toIfc } from 'brepjs-bim';

const model = new BimModel();
model.init({ name: 'Example' });

// Spatial structure: project → site → building → storey.
const project = model.getProject();
const siteId = model.addSite({ name: 'Site' });
const buildingId = model.addBuilding({ name: 'Building' });
const storeyId = model.addStorey({ name: 'Level 1', elevation: 0 });
if (project) model.aggregate(project.localId, siteId);
model.aggregate(siteId, buildingId);
model.aggregate(buildingId, storeyId);

// A parametric wall, placed on the storey. Dimensions in mm; axisX is the wall's
// length direction and axisZ its up direction.
const wall = model.addWall({
  length: 4000,
  height: 3000,
  thickness: 200,
  origin: [0, 0, 0],
  axisX: [1, 0, 0],
  axisZ: [0, 0, 1],
  materialName: 'Concrete',
});
if (wall.ok) model.placeIn(wall.value, storeyId);

// Renderable geometry (a brepjs ValidSolid, unplaced/local coords):
const solid = model.getWalls()[0]?.geometry;

// Serialize to an IFC-SPF byte buffer.
const ifc = await toIfc(model, { name: 'Example', author: 'brepjs-bim' });
// ifc.ok && ifc.value instanceof Uint8Array

Reading element geometry requires only the core brepjs kernel; toIfc / fromIfc additionally load the web-ifc peer dependency.

All public operations return Result<T, BimError> (from brepjs); validation issues and non-fatal warnings travel inside the payload rather than throwing.

Design

Each add* call parses and validates the spec (the parse*Spec functions are also exported for standalone use), builds the brepjs solid analytically from the spec, and stores a typed BimElement keyed by a LocalId. The IFC writer walks the model, applies placement, and emits schema-correct IFC entities; the importer is the inverse. No kernel/WASM changes are required.

Development

npm run typecheck --workspace=brepjs-bim
npm run lint --workspace=brepjs-bim
npm run build --workspace=brepjs-bim
npm run test --workspace=brepjs-bim