ironstream (Python bindings)

PyO3 bindings for the IronStream CAD geometry kernel — a from-scratch, zero-dependency Rust port of OpenCascade.

This is one of three consumption paths off the IronStream kernel (the other two — native Rust and a WASM/TypeScript export — live elsewhere). It mirrors the kernel's OCCT-shaped prelude, in the spirit of pyOCCT: symbols are available both flat and under OCCT-style submodules.

import ironstream as ist

box = ist.make_box(ist.Pnt(0, 0, 0), 20, 20, 20)
hole = ist.make_cylinder(5, 20)
part = ist.cut(box, hole)
print(part.volume())

with open("part.stl", "wb") as f:
    f.write(ist.write_binary_stl(part.mesh()))

pyOCCT-style namespaces are also available:

from ironstream.gp import Pnt
from ironstream.prim import make_box
from ironstream.algo import cut

Layout

Development

Requires a Rust toolchain and maturin. The kernel is pulled in as a local path dependency (../ironstream), so clone both repos as siblings.

uv venv
maturin develop            # builds the kernel + binding, installs into the venv
python -c "import ironstream; print(ironstream.make_box(ironstream.Pnt(0,0,0),1,1,1).volume())"

Build a distributable wheel with maturin build --release.

Pyodide / WebAssembly

The binding also builds as a Pyodide wheel (~140 KB) that runs the whole kernel in the browser — this powers the live demo on the IronStream project page:

chmod +x scripts/build_pyodide_wheel.sh
./scripts/build_pyodide_wheel.sh    # -> dist/cadbuildr_ironstream-*-emscripten_*_wasm32.whl

The script pins the full toolchain (pyodide xbuildenv 0.29.4, emscripten 4.0.9, rust nightly-2025-02-01 + pyodide's wasm-eh sysroot) and documents why each pin exists. Load it in a page with:

const { loadPyodide } = await import("https://cdn.jsdelivr.net/pyodide/v0.29.4/full/pyodide.mjs");
const py = await loadPyodide({ indexURL: "https://cdn.jsdelivr.net/pyodide/v0.29.4/full/" });
await py.loadPackage("<url of the .whl>");
py.runPython(`import ironstream as ist; print(ist.make_sphere(10).volume())`);