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Concepts

Understanding-oriented. The why behind apeGmsh, not the how.

apeGmsh makes a handful of deliberate choices — a session owns one Gmsh kernel, composites split by concern, you address geometry by name and never by raw tag, the FEMData snapshot is the solver contract, and the OpenSees bridge is typed rather than string-templated. None of that is arbitrary. Once the mental model clicks, the API stops feeling like a pile of methods to memorize and starts feeling like one idea applied consistently.

These pages are for reading in an armchair, not for copy-pasting. When you want to do a specific thing, the How-to recipes are faster. When you want to learn the workflow hands-on, start with the Tutorials. Come here when you want to understand why it's built this way — so you can predict how it behaves instead of guessing.

Start here

→ The apeGmsh mental model

One short page — about a screen and a half — covering the few ideas the whole library rests on: the session and its kernel, composites by concern, the tag / label / physical-group distinction, .select(), the immutable FEMData snapshot, declare-then-resolve, and the typed bridge. If you read one Concepts page, read this one. Everything else fills in detail.

Going deeper

The topic guides below explain individual subsystems. They're the de-blended descendants of the old long-form walkthrough — each one leads with the idea, then shows it in code.

The session and its abstractions

  • The session — the session lifecycle, composites, the shape of a typical script, and when geometry belongs to a reusable Part rather than the session itself.
  • Selection & queries — why you address geometry by name, the .select() vocabulary, and how queries resolve to entities.

Geometry, meshing & assembly

  • Geometry & CAD — authored geometry, STEP import and healing, naming imported faces by query, and transforms.
  • Meshing — mesh sizing, fields, structured meshing, and what partitioning is for.
  • Parts & assembly — Part templates, placement, and fragmenting an assembly into a conformal whole.

Physics: loads, masses & constraints

  • Loads & masses — the declare-then-resolve pipeline for forces, pressures, gravity, prescribed displacements, and mass.
  • Constraints — equalDOF, ties, rigid links, diaphragms, and contact — and the rule that MP constraints emit automatically through the bridge.
  • Sections — declaring sections, the in-process section-property analyzer, and how both reach the solver.

The solver contract & results

  • The FEM broker (FEMData) — the immutable snapshot every solver bridge consumes, and why it's frozen.
  • The OpenSees bridge — the typed apeSees(fem) surface: typed primitives instead of raw ops.* strings.
  • Results — the Results container: three constructors, one read API, and how names flow back out of a solve.

Next: Core concepts (the mental model).