stroblme 2c2c4e4712 10C Inc 1: core modeling
Binds the modeling core the app builds every feature out of — 93 of its 138
symbols now resolve, up from 34. New modules: GeomAbs, Geom2d, Geom,
TCollection, TColgp, TColStd, GProp, BRepGProp, Bnd, BRepBndLib, Adaptor3d,
BRepAdaptor, GeomLProp, GeomAPI, BRepBuilderAPI, BOPAlgo, BRepAlgoAPI,
BRepPrimAPI, GC, BRepMesh; gp and BRep_Tool completed.

Three structural decisions:

- BRepBuilderAPI_MakeShape carries Build/Shape/Generated/Modified/IsDeleted for
  every maker in the binding, so the booleans, the primitives and (later) the
  fillet builders all answer the app's duck-typed provenance layer through
  ordinary virtual dispatch. History lists come back copied, so they outlive
  the builder.
- The executing two-argument BRepAlgoAPI constructors stay unbound; operands go
  in through SetArguments/SetTools. Section keeps Init1/Init2, which are plain
  setters. BOPAlgo moved up from Inc 2 — SetGlue needs its enum.
- Adaptor3d is registered although the app never imports it: every method it
  calls on BRepAdaptor_Curve/Surface is a virtual declared there, so binding
  them once on the bases leaves mod_BRepAdaptor.cpp with just constructors.

Gate: tests/test_inc1_modeling.py against reference values gen_fixtures.py now
records from the stock wheel — measurements, per-face area/centroid in map
order, mesh counts, and the boolean history map compared exactly, since that is
the substrate the app's topological naming is built on.

tools/sigdiff.py compares our bound surface against stock's, because a wrong
nb::init<> is silent: MakePrism's five-argument form bound OCCT's semi-infinite
gp_Dir overload (gp_Dir converts from gp_Vec), producing a valid solid of the
wrong shape with the flags shifted along. The fixture digest caught it; sigdiff
finds the class of bug directly, and now reports only one deliberate deviation.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DfriM8XUkn7uYf5Dwe2xo6
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up
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n3xd-ocp

Hand-written nanobind bindings for the OpenCASCADE (OCCT) geometry kernel, covering exactly the surface the N3XD CAD backend uses — 139 symbols across 48 OCP.* modules, not all of OCCT.

The package installs as a top-level OCP, so it is a drop-in replacement for cadquery-ocp-novtk and the app's 442 import sites stay untouched.

Status: Inc 0 (spike) shipped — build system, OCCT builder image, handle model, and the first module surface (gp, TopAbs, TopoDS, TopExp, TopLoc, TopTools, BRep, BinTools, Poly, Standard), published as 7.9.3.1.dev1. BREP serialisation is byte-identical to the stock wheel, which is the gate that mattered: the pools and the content-addressed derive payloads both depend on it. Coverage is 34 of the 139 symbols the app imports; the rest lands in increments 1-4 (roadmap 10C).

Start with docs/design.md for the decisions, docs/building.md to build one, and docs/adding-symbols.md to extend the surface. The phase plan lives in the app repo at docs-private/reference/roadmap.md (Phase 10).

Why

cadquery-ocp lags OCCT (it wraps 7.9.3; OCCT 8.0 shipped 2026-05), builds Windows and macOS wheels we never use, and until recently forced a 638 MB VTK dependency into the image. Binding call overhead is not a bottleneck — the CAD hotspots live inside the C++ kernel — so this exists for version velocity, footprint, and two defects that a binding we control prevents by construction:

  • OCCT sub-shapes are returned by value, so a wrapper can never alias a TShape whose owner has died (this segfaulted a process-global face memo).
  • Executing constructors (the two-argument BRepAlgoAPI_* forms) are not bound, so the double-execution footgun is unrepresentable.

It also releases the GIL around kernel calls and ships type stubs, neither of which upstream does.

Build

OCCT is compiled once into a builder image and reused; it is never built on the production host (4 cores, and a kernel build is multi-hour). Wheels are built here on a dev box and published to the Gitea package registry.

make image    # once, ~40 min: compiles OCCT 7.9.3 into the builder image
make dev      # inner loop: incremental compile + tests
make wheel    # compile, stubs, auditwheel, self-containment smoke test
make publish  # -> https://git.stroblme.de/api/packages/N3XD/pypi

Credentials go in .secrets (gitignored) as UV_PUBLISH_USERNAME / UV_PUBLISH_PASSWORD. Consumers read anonymously — the package is public:

uv pip install --index-url https://git.stroblme.de/api/packages/N3XD/pypi/simple/ \
    --prerelease=allow n3xd-ocp

Versions are <occt-version>.N, enforced at configure time against the OCCT actually found, so the kernel a wheel wraps is readable from its version alone. The registry refuses to republish a version; iteration builds therefore carry a .devN suffix and are the only ones the registry's cleanup rule collects.

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