ANYmesher

Structured meshing for shell and beam finite-element models described by ANYgeometry: edge seeding and local refinement, a built-in mapped (transfinite Coons) mesher, mapped-face decomposition, optional Gmsh meshing, geometry-to-mesh associations, quality metrics, a tkinter mesher and a command-line interface.

After the first package-index release, install with python -m pip install ANYmesher. Until then, use the editable development setup below.

The repository is ANYmesh, but anymesh was already taken on PyPI, so the distribution is ANYmesher and the import package is anymesher.

Quick start

A stiffened panel needs no geometry model:

import anymesher as am

panel = am.StiffenedPanel(
    length=4.0, width=3.0, plate_thickness=0.012,
    num_stiffeners=2, stiffener_spacing=1.0,
    stiffener_height=0.30, stiffener_web_thickness=0.010,
    stiffener_flange_width=0.150, stiffener_flange_thickness=0.015,
)
mesh = am.stiffened_panel_mesh(panel, am.PanelMeshConfig(
    shell_num_divisions_x=8, shell_num_divisions_y=6, beam_num_divisions=8,
))

mesh.num_nodes, len(mesh.quads), len(mesh.beams), len(mesh.couplings)
am.panel_edge_nodes(mesh)["x0"]          # the nodes on the x = 0 edge
am.verify_mesh_quality(mesh).max_aspect_ratio

Anything less regular goes through the shared geometry model:

import anygeometry as ag

model = ag.GeometryModel()
points = model.add_points([(0, 0, 0), (2, 0, 0), (2, 1, 0), (0, 1, 0)])
face = model.add_face(model.add_polyline(points, close=True))

am.punch_circular_hole(model, face, (1.0, 0.5, 0.0), 0.2)
mesh = am.generate_mesh(model, target_size=0.05, order="quadratic")
mesh.nodes_on(ag.EntityRef("edge", 3))   # still addressable after re-meshing

anymesher.geometry remains as a temporary compatibility import. Its classes are the exact ANYgeometry classes, not converted copies, but new code should import geometry directly from anygeometry.

Command line

anymesher panel --length 4 --width 3 --thickness 0.012 --height 0.3 --web-thickness 0.01 --divisions-x 8 --divisions-y 6

panel, plate, beam, quality and backends, each with --json. --output writes the mesh as JSON.

anymesher-gui opens the mesher: enter a panel, plate or beam, watch it re-mesh as you type, read the quality report, and save the result. It is deliberately not a geometry editor — building a BRep interactively is an application's job, and ANYfem already does it.

Applications can put that form behind their own mesh button. Passing a callback adds a Use mesh button and returns the neutral Mesh directly:

from anymesher.gui import open_mesher

window, mesher = open_mesher(root, on_apply=project.replace_mesh)

The host remains responsible for deciding whether a generic neutral mesh is appropriate for its structural model.

What a mesh is here

generate_mesh returns nodes, quadrilaterals, triangles, beams, coupling records, and the association back to the geometry: which node came from which vertex, which nodes lie along which edge, which elements belong to which face.

The association is the point. It is what lets a load or a restraint be named against geometry and survive a re-mesh, and what makes results addressable by the thing the user drew rather than by node number. Primitives fill the same fields against synthetic entity IDs, so a consumer needs one lookup path either way.

Backends

am.generate_mesh(model, backend="gmsh", target_size=0.1)

The two are not interchangeable in what they guarantee, and the differences are recorded rather than smoothed over: an unstructured mesh has no (i, j) index, so that field is left empty instead of filled with something plausible. Planar boundaries may contain ANYgeometry straight lines, circular arcs or Bezier splines; Gmsh receives each as its corresponding exact curve primitive.

Native triangulation

Mapped/native face selection is separate from the triangulator used after a face has selected the native strategy. In 0.2.1, omitted native_backend and planar backend arguments default to "auto": an explicitly registered boundary is preferred, then the built-in compiled boundary, with the deterministic Python reference used only when native capability is absent.

Use "python" to require the compatibility/reference implementation and "native" to require compiled capability without fallback. Import or execution failure from a present but corrupt extension is reported; it is never treated as ordinary absence. ANYfem format 6 persists this selector explicitly, while its format 1-5 migration writes "python" so old projects retain their behavior.

Design notes

One shared geometry authority. ANYmesher never converts a geometry model. It consumes the same GeometryModel and EntityRef objects that applications use for selections and attributes, then records associations to their stable IDs.

Conformity by construction. Node generation order is fixed: one node per used vertex, then n - 1 interior nodes per edge in the edge's own direction, then face interior nodes from the Coons blend. Neighbouring faces look their boundary nodes up from the same registries, so they share the very same nodes. The alternative — meshing faces independently and merging coincident nodes within a tolerance — fails quietly on nearly-coincident geometry and produces a mesh that looks connected and is not.

Coupling records, not constraints. When a stiffener stands off the plating, the mesher records per beam node: the shell element it projects into, the shape weights at that point, and the eccentricity vector. That is a statement about geometry. Deciding it becomes six multi-point constraints is the consuming solver's business. Interpolating through the shape functions is what removes the older requirement that a beam node lie on a shell node row, so the mesh no longer has to be aligned to the stiffeners for the coupling to be exact.

Numbering is a contract. A consumer stores results per node and element ID, so a renumbering that is mathematically irrelevant still invalidates its baselines. The primitives number shell nodes from 1, beam nodes from 10000, beam elements from 20000 and couplings from 30000; the mapped mesher numbers by registry order. Both are documented where they are implemented and asserted by test.

See docs/ARCHITECTURE.md for the layering, and MIGRATION.md for what was extracted from where.

Scope

Out of scope: geometry ownership, elements, materials, assembly and solution. General splitting, trimming, projection, transforms and intersections belong to ANYgeometry. check_mappable, triangle_to_quads and the four-patch butterfly hole decomposition stay here because they exist specifically for mapped quads. The convenience workflow generate_mesh_with_intersections reuses ANYgeometry's qualified intersection imprint on a temporary clone before mapped meshing; it does not introduce a second geometric intersection kernel. The same workflow also makes structural beam joints explicit: coincident beam ends share a node, a beam ending on or crossing another straight beam splits the receiving spans, and beam nodes on a shell use either the coincident shell node or an interpolation coupling. The design geometry remains unwelded and all associations are folded back to its original owners. At a qualified shell T-junction, boundary nodes of the terminating shell are likewise attached to the interior support shell with interpolation records; crossing shell interiors still require conformal imprinting and fail closed if the topology cannot be qualified. The legacy anymesher.split_face_at, split_face_between and strip_face imports likewise retain their mapped-partition semantics; new neutral geometry code should import the general edit operations from anygeometry. Writing a mesh to a .fem or .inp file belongs to ANYfileio, which depends on this package — so the arrow cannot point back. The JSON in anymesher.serialize is the mesh container written out as itself, not an interchange format.

Units

SI throughout, lengths in m. There is no conversion layer. The mesher window accepts mm because that is how plate and profile dimensions are quoted, and converts at the widget.

Development

python -m pip install --no-deps -e C:\Github\ANYgeometry
python -m pip install -e "C:\Github\ANYmesh[dev,gmsh]"
python -m pytest

To open the mesher straight from a checkout — including an IDE's Run button, with nothing installed — run run_gui.py at the repository root.

python run_gui.py