FEM Region Mesh API¶

Python API¶

The complete runnable example is in the numbered example section below; the exact callable fields and arguments are in the numbered API section. These values are copied from the current Python contract, not inferred from the UI.

Symbols and SI units¶

All geometric lengths use \(\mathrm{m}\); dimensionless selectors use \(1\).

Assumptions and validity¶

Authoring validation does not prove mesh generation or solver qualification; the realized report is authoritative.

1. What it is and when to use it¶

An object-owned region mesh policy refines a named region inside the shared FEM domain. Use it for local size/order/transition control; it does not create an independent solver mesh.

2. Physical and mathematical explanation¶

The region policy selects a local finite-element resolution. It has no own physical equation; its effect is through the local discrete space and shared- domain conformity constraints.

3. Example - complete Python script¶

# %% Region-local FEM mesh policy
import fullmag as fm

nm = 1.0e-9
study = fm.study("fem_region_mesh")
study.engine("fem")
study.device("cpu", precision="double")
study.mode("strict")
body = study.geometry(fm.Box(80 * nm, 40 * nm, 4 * nm), name="film")
region = body.add_region("core", fm.Box(40 * nm, 20 * nm, 4 * nm))
region.mesh(maximum_element_size=3 * nm, minimum_element_size=1.5 * nm,
            transition_distance=5 * nm, order=1)
body.Ms = 800.0e3
body.Aex = 13.0e-12
body.m = fm.texture.uniform(1.0, 0.0, 0.0)
study.exchange()
study.demag(realization="poisson_robin")
study.build_domain_mesh()
study.stages.add_relax(
    stage_id="equilibrium",
    algorithm="llg_overdamped",
    tolA=1.0e-4,
    max_steps=1_000,
)

4. Exact API¶

ObjectRegion.mesh rejects minimum_element_size > maximum_element_size and invalid positive-value constraints. The policy is serialized into the owning object’s region mesh specification.

ProblemIR¶

The request lowers to the mesh-workflow or discretization subtree; requested intent remains distinct from the resolved mesh asset and provenance report.

Round-trip and failure semantics¶

Requested intent is the Python policy; resolved execution is the realized mesh report. Validation errors identify the violated domain rule, and unsupported combinations fail explicitly without silent fallback.

Discrete realization¶

The backend consumes the realized Cartesian or finite-element asset, including topology, markers, quality, and provenance where available.

5. How to set it in Control Room¶

Route: Model Explorer -> Objects -> <object> -> Regions -> <region> -> Mesh. Enable the regional override, set maximum/minimum size, transition distance, and order, then press Apply. Build Shared-Domain Mesh materializes the conforming result and refreshes region resources. See Control Room capability register.

6. Backend and frontend support¶

Validation¶

Focused constructor, lowering, and mesh-report tests are the evidence boundary for this page.

7. Limitations and known pitfalls¶

• A region policy cannot create an overlapping independent submesh.

• Selector and native marker resolution must succeed before it affects elements.

• Final conformity and values belong to the build report.

8. Scientific bibliography¶

1. P. G. Ciarlet, The Finite Element Method for Elliptic Problems, SIAM, 2002.

2. C. Geuzaine and J.-F. Remacle, “Gmsh: a three-dimensional finite element mesh generator,” International Journal for Numerical Methods in Engineering 79, 1309-1331 (2009), doi:10.1002/nme.2579.

9. Source-code index¶

Source-code index¶

• Python contract source: packages/fullmag-py/src/fullmag/model/discretization.py and packages/fullmag-py/src/fullmag/world.py, where applicable. Backend realization is in the relevant backends/fdm or backends/fem lane named by the page.