OpenMCAD

A parametric, feature-based mechanical CAD system for Windows, built on .NET 10.

Status: Phase 2 of 17 — the viewport. The kernel is real (OCCT 8.0.1 behind a C ABI shim), the application opens on shaded geometry with edges, and picking works. There is no document model, no sketcher and no file format yet. See docs/plan.md for the full plan and what each phase still owes.

What this is meant to become

History-based parametric part modelling, a fully constrained 2D sketcher, assemblies with mates and an assembly-level solve, associative production drawings generated by hidden-line removal, STEP AP242 and other exchange formats, sheet metal, surfacing, and a stable public plugin API.

What exists today

Solution and layered project skeleton	✅ P0-T04
Layering enforced by architecture tests	✅ P0-T05
Double-precision geometry primitives (OpenMCAD.Math)	✅ P0-T13
WPF shell that launches, with ribbon and docking	✅ P0-T10
Headless CLI (omcad)	✅ P0-T11
Structured logging and DI composition root	✅ P0-T09
Native shim skeleton (CMake, C ABI, exception firewall)	✅ P0-T06 — authored, not yet linked to OCCT
Kernel abstraction, single-threaded dispatcher, owning handles	✅ P1-T01/02/07/08
FakeKernel — deterministic analytic mock	✅ P1-T09
Kernel contract battery	✅ P1-T10
C ABI generated from a single IDL (49 operations)	✅ P1-T03
Repro-bundle capture, regression corpus, determinism gate	✅ P1-T13, P1-T14
OCCT 8.0.1 built and verified (spike)	✅
OCCT behind IGeometryKernel	⬜ P1-T04/05/06 — next
Viewport	⬜ Phase 2
Documents, rebuild, topological naming	⬜ Phase 3
Sketcher	⬜ Phase 4

Building

Requirements:

• .NET 10 SDK (pinned in global.json)
• Visual Studio Build Tools with the C++ workload — only for the native shims. Without it the build skips them and everything managed still builds and runs.
• CMake 3.25+ — same condition.

./build.ps1                                  # Debug build, then tests
./build.ps1 -Configuration Release           # Release
./build.ps1 -SkipTests                       # Build only
./build.ps1 -Clean                           # Clean first

Outputs land under artifacts/bin/:

• OpenMCAD.Shell/<config>/OpenMCAD.exe — the application
• OpenMCAD.Cli/<config>/omcad.exe — the headless runner

./artifacts/bin/OpenMCAD.Cli/debug/omcad.exe version

Logs are written to %LOCALAPPDATA%\OpenMCAD\logs.

Tests

xunit.v3 runs on Microsoft.Testing.Platform, and each test project builds as its own executable test host. build.ps1 invokes those hosts directly rather than using dotnet test; see docs/notes/test-runner.md for why.

./artifacts/bin/OpenMCAD.Math.Tests/debug/OpenMCAD.Math.Tests.exe

Repository layout

docs/            PLAN.md (the master plan) · adr/ · specs/ · notes/
native/          C ABI shims over OCCT and planegcs · vcpkg manifest · CMake
src/             one project per architectural layer; dependencies point downward only
tests/           unit · integration · regression corpus · fuzz · perf · arch

Layer order is declared in docs/PLAN.md section 4.1 and enforced by tests/arch/OpenMCAD.Architecture.Tests, which checks both the compiled metadata and the project graph. A reference that points sideways or upward fails the build.

Contributing

Read docs/PLAN.md section 12 before starting. In short:

• Work phase by phase. Announce the task ID you are doing.
• Commit as P<n>-T<nn>: <imperative summary>, and tick the box in docs/PLAN.md in the same commit.
• A geometry change without corpus coverage is not done. A naming regression is a P0.
• No new NuGet dependency without an ADR (docs/adr/).
• Do not improve the architecture opportunistically. Write an ADR proposal and stop.

How this was built

OpenMCAD is an experiment in how far an AI coding agent can get building a system of this size, working from docs/PLAN.md phase by phase under human direction. Essentially all of the code here was written by Claude. That is the point of the repository, and it is stated plainly rather than left to be inferred — judge the code accordingly.

Licence

MIT.

Third-party components keep their own licences; see THIRD-PARTY-NOTICES.md. The geometry kernel (OCCT) and constraint solver (planegcs) are LGPL-2.1 and are confined to separately replaceable dynamic libraries, which is both the engineering design (ADR-0003, ADR-0006) and what the LGPL relinking condition asks for. See ADR-0017 for the full reasoning.