Introduction

ogeom is a boundary-representation (B-rep) CAD kernel written from scratch in Rust. It does not wrap, vendor or link any existing CAD kernel.

What it covers

• Parametric curves and surfaces.
• Shared B-rep topology with per-entity tolerances and operation history.
• Booleans, blends and chamfers, offsets and shells, sweeps and lofts.
• Healing and tessellation.
• Product structure (assemblies) and 2D drawings with hidden-line removal.
• Data exchange:
  • STEP, read and write, with assemblies, colours, semantic PMI and saved views.
  • IGES, read and write.
  • The native document format.
  • Mesh formats. Meshes can be turned back into solids, with their curved regions recognized.

How this book is kept honest

• Examples are tested. Every code block in this guide comes from a test file that runs in CI, so a broken or false example fails the build. The test suite checks every numeric claim against a closed form or a round trip.
• Completeness is audited. Scope sets the target: parity with the reference kernel’s four modelling modules, plus meshes into solids. The parity ledger is committed and machine-checked: it maps every public header of those modules to a named capability, and each verdict cites symbols and tests the build verifies.

Where things are

• This guide: concepts and workflows, in reading order.
• The API reference: rustdoc for the ogeom umbrella crate. Depend on that crate. The crates under it are an implementation detail and will change.
• The repository: source, issues, and the governing documents this book includes verbatim.