wn-geometer 2026.5.23

Python bindings for Geometer CAD geometry operations

Geometer

Focused C++ geometry library and CLI built on OCCT. Provides a small, controllable interface for operations like STEP-to-GLB conversion, HLR projection, planar boolean/offset solving, and polygon extrusion/meshing.

Interfaces

Current C++, C ABI, Python, WASM, and CLI interfaces are documented in INTERFACES.md.

Build

cmake --preset default
cmake --build build --config Release

On first configure, CMake automatically builds OCCT from source (~10-15 min one-time cost). Subsequent configures are instant.

To manually rebuild OCCT (e.g., after version bump or to clean):

python scripts/build_occt.py --clean
python scripts/build_occt.py

The Python package direction is executable-backed: bundle a platform geometer CLI and have Python call it through a subprocess. That keeps the CLI useful on its own and avoids native library loading issues in Python. The CLI now has a JSON batch command so repeated STEP operations can run in one process.

WASM Build

python scripts/build_wasm.py

This installs emsdk, cross-compiles OCCT, and builds geometer for WASM. First run takes ~20-30 min. Outputs land in dist/wasm/ with flat compatibility copies at the root of dist/.

The WASM build produces three targets:

• dist/wasm/browser/geometer.js + dist/wasm/browser/geometer.wasm - official browser/Web Worker integration target. This is the full OCCT-backed build exporting createGeometerModule and the flat C ABI, including STEP bytes to GLB bytes, HLR projection, and planar byte APIs.
• dist/wasm/node-test/geometer-node-test.js + dist/wasm/node-test/geometer-node-test.wasm - Node CLI parity/test target with filesystem access. Use this for tests and diagnostics, not browser integration.
• dist/wasm/planar-browser/geometer-planar-browser.js + dist/wasm/planar-browser/geometer-planar-browser.wasm - smaller optional browser/Web Worker target exporting createGeometerPlanarModule and the planar byte APIs only. It exists so planar-only consumers can avoid paying the full OCCT/STEP WASM size, startup, and worker-memory cost.

Native builds copy platform-specific artifacts under dist/native/<platform>/, using names such as windows-x64, linux-x64, macos-x64, and macos-arm64. Flat files at the root of dist/ are retained as compatibility aliases during the transition to the grouped layout.

dist/ is the committed distribution directory. .deps/, build/, build-native/, and build-wasm/ are local generated state and are not committed.

Usage

Python distribution name: wn-geometer.

Python import package name: geometer.

Native:

geometer --version
geometer step-to-glb input.step output.glb
geometer step-to-glb input.step output.glb --deflection 0.05 --angular 0.3
geometer step-project-hlr input.step output.json
geometer step-project-svg input.step output.svg --mode simple --view top
geometer step-project-svg input.step output.svg --mode detail --curve-mode native-arcs
geometer init-request request.json --step input.step --operation step_hlr_projection_json --output output.json
geometer run request.json response.json

Batch request JSON accepts a top-level options object for settings shared by all jobs. A job-level options object overrides those defaults for that job.

WASM (via Node.js):

node dist/wasm/node-test/geometer-node-test.js step-to-glb input.step output.glb

Python from a source checkout:

cmake --build build --target geometer --config Release
python -m pytest tests/python

from pathlib import Path
import geometer

version = geometer.version()
projection = geometer.project_step_hlr(
    Path("part.step"),
    views=[geometer.ProjectionView.top()],
)
glb_bytes = geometer.step_to_glb(Path("part.step"))

response = geometer.run_batch(
    [
        {
            "id": "part-top",
            "operation": "step_hlr_projection_json",
            "step_path": "part.step",
            "output_path": "part.top.projection.json",
        }
    ],
    options={"curve_mode": "polyline"},
)

runner = geometer.GeometerBatchRunner(max_workers=8, chunk_size=5)
runner_version = runner.version()
response = runner.run(
    [
        {
            "id": "part-top",
            "operation": "step_hlr_projection_json",
            "step_path": "part.step",
            "output_path": "part.top.projection.json",
        }
    ],
    options={"curve_mode": "polyline"},
)

Python uses the bundled wheel executable or source-checkout dist/native/<platform>/geometer(.exe) by default through the CLI JSON batch mode. The legacy flat dist/geometer.exe / dist/geometer path is still accepted. Set GEOMETER_EXE to override the executable path. The Python package intentionally uses the executable backend only for now.

Build a local Python wheel after building the native CLI. Keep Python package artifacts under out/wheelhouse; repo dist/ is reserved for Geometer runtime artifacts:

python -m build --wheel --outdir out/wheelhouse
python -m twine check out/wheelhouse/*.whl

Embedded model browser viewer:

powershell -NoProfile -ExecutionPolicy Bypass -File scripts/prepare_embedded_model_fixtures.ps1
python -m http.server 8123 --bind 127.0.0.1

Open http://127.0.0.1:8123/tests/wasm/embedded_model_viewer.html.

HLR benchmark page:

http://127.0.0.1:8123/tests/wasm/hlr_benchmark.html

Examples:

• examples/python/pyvista_hlr_viewer.py - PyVista/Qt STEP 3D + HLR preview.
• examples/python/hlr_viewer.py - Dear PyGui STEP HLR fallback viewer.
• examples/wasm/ - browser/WASM example home, with current test-backed pages still under tests/wasm/.

Dependencies

• OpenCASCADE Technology (V7_8_1) - built from source automatically.
• RapidJSON (v1.1.0, header-only) - vendored in third_party/rapidjson for OCCT glTF export.
• Clipper2 (2.0.1) - vendored in third_party/clipper2 for planar polygon boolean and offset operations.
• Python 3 - needed by scripts/build_occt.py (invoked by CMake on first configure).

Project structure

• src/cpp/lib/ - libgeometer, the reusable C++ core.
• src/cpp/cli/ - geometer CLI executable.
• python/geometer/ - Python package using the native CLI by default.
• examples/ - user-facing Python and browser/WASM examples.
• third_party/ - small vendored source dependencies used by the build.
• tests/ - rack-based stratified test system.
• docs/adr/ - architecture decision records.
• docs/requirements/ - requirements.
• docs/plans/ - work plans.
• scripts/ - build and tooling scripts (uv-managed Python).