brepjs

CAD modeling for JavaScript.

Getting Started · Cheat Sheet · Docs

Shapes are exact mathematical boundaries - not triangle meshes - so booleans are precise, measurements are real, and you can export to STEP. TypeScript types prove the geometry is valid at compile time.

// Drill a hole, fillet the vertical edges, export to STEP
import { box, cut, cylinder, fillet, edgeFinder, exportSTEP, unwrap } from 'brepjs/quick';

const b = box(30, 20, 10);
const hole = cylinder(5, 15, { at: [15, 10, -2] });
const drilled = unwrap(cut(b, hole));

const edges = edgeFinder().inDirection('Z').findAll(drilled);
const part = unwrap(fillet(drilled, edges, 1.5));

const step = unwrap(exportSTEP(part));

Why?

brepjs grew out of the love and care I put into gridfinitylayouttool.com. I needed parametric CAD in the browser and I'm not a 3D modeler, but I know TypeScript. OpenSCAD nailed code-first CAD but lives outside the JS ecosystem. replicad proved OpenCascade works in JS but I kept hitting performance walls and fighting the API.

Neither had the type safety I wanted, so brepjs leans hard on it: branded types, Result<T,E>, phantom types that prove invariants at compile time. If it compiles, the geometry is valid. Best for parts defined by parameters (enclosures, brackets, fixtures, gridfinity bins) rather than organic sculpting.

Status

Production-ready with the OpenCascade kernel. brepkit, a Rust-based kernel, is in active development as a faster replacement but not yet production-ready. The kernel abstraction layer means switching is a one-line change. See benchmarks for performance comparisons.

Install

npm install brepjs brepjs-opencascade

brepjs/quick handles WASM init automatically via top-level await (ESM only). Other options:

// Auto-detect kernel
import { init } from 'brepjs';
await init();

// Or manual setup
import opencascade from 'brepjs-opencascade';
import { initFromOC } from 'brepjs';
const oc = await opencascade();
initFromOC(oc);

Architecture

Layer 3  sketching/, text/, projection/   High-level API
Layer 2  topology/, operations/, 2d/ ...  Domain logic
Layer 1  core/                            Types, memory, errors
Layer 0  kernel/, utils/                  WASM bindings

Imports flow downward only. Boundaries are enforced in CI.

Documentation

• Getting Started: Install, create shapes, export to STEP
• B-Rep Concepts: Vertices, edges, faces, solids - and why they matter
• Which API?: Fluent wrapper vs Sketcher vs functional
• Cheat Sheet: Single-page quick reference
• Cookbook: 21 practical recipes for common CAD workflows
• Three.js Integration: Render brepjs shapes in the browser
• Function Lookup: Alphabetical index of every export
• Error Reference: Error codes and recovery
• API Reference: Searchable TypeDoc reference
• Memory Management: WASM resource cleanup patterns
• Performance: Optimization tips
• Custom Kernels: Swap or write your own geometry kernel
• Architecture: Layer diagram and module overview
• Compatibility: Tested environments

Projects Using brepjs

• Gridfinity Layout Tool: Web-based layout generator for Gridfinity storage systems

Contributing

See CONTRIBUTING.md for development setup and guidelines.

License

Apache-2.0