rapidmesh

Conforming tetrahedral and surface meshes for finite element and finite volume solvers. The mesher is written in Rust; this package is a thin layer over its API, so everything here is also available to Rust programs.

• Primitives, CAD files and exact CSG: boxes, cylinders, spheres, cones, tori, prisms, sweeps, helices, lofts, fillets and chamfers, sheets, STEP files and STL/OBJ imports, united and cut by an exact arrangement. Material interfaces stay exactly conforming.
• Bottom-up meshing: edges, then each face on its analytic surface, then each region on its own, with hierarchical sizing per region, geometric face and geometric edge. Thin layers take flat tets instead of being refined to their thickness.
• Solver output: topology with orientation signs, the geometric entity of every face and edge, named sets, periodic point pairs, gmsh MSH 4.1, VTU, OpenFOAM polyMesh with tets or polyhedral cells (mesh.write_foam(case, polyhedral=True)), CalculiX/Abaqus (mesh.write_inp(path, order=2)), second-order tets on the true geometry (mesh.second_order()), finite volume quality (mesh.fvm_quality()).

Install

pip install rapidmesh

Usage

import rapidmesh as rm

g = rm.Geometry(maxh=0.5)
air = g.box(10, 10, 13.6)
sub = g.box(10, 10, 1.6, maxh=0.8)
g.label(air, "air")
g.label(sub, "substrate")
g.xy_plate(6, 6, position=(2, 2, 1.6), tag=1)   # a PEC patch
g.label(1, "patch")

# a periodic unit cell, and a named port face
g.periodic(g.surf(normal=(-1, 0, 0)), g.surf(normal=(1, 0, 0)))
g.periodic(g.surf(normal=(0, -1, 0)), g.surf(normal=(0, 1, 0)))
g.surf(near=(5, 5, 13.6)).name = "port"

mesh = g.mesh()
print(mesh)                 # Mesh(... tets, ... points, min dihedral ... deg, ... ms)

mesh.points                 # (n_points, 3) float64
mesh.tets                   # (n_tets, 4)   uint64
mesh.tet_regions            # region tag per tet
mesh.topology               # edges, faces, incidence with signs, classification
mesh.sets()                 # {"cells": ..., "faces": ..., "edges": ...} by name
mesh.periodic_points        # (n, 2) point on a master face and its image
mesh.write_msh("cell.msh")  # physical groups from the labels and names

CAD files

g = rm.Geometry(maxh=2.0)
bodies = g.import_step("assembly.step")   # one solid per body of the file
mesh = g.mesh()                           # faces meshed on their true surfaces

STEP files (AP203 and AP214) bring planes, cylinders, cones, spheres, tori and B-spline surfaces; coordinates stay in the file's unit. Each solid takes the name the file gives its part, so an assembly's mesh has its parts as named sets and physical groups.

Sizing

g.maxh = 0.5                               # global target size
g.region(2).maxh = 0.2                     # one region
g.surf(normal=(0, 0, 1)).maxh = 0.1        # the faces facing +z
g.edge(near=(0, 0, 1)).maxh = 0.05         # the edge nearest a point
g.tol = 1e-3                               # chord tolerance of curved entities
g.refine_near_points([(1, 1, 1)], 0.02)    # point size sources
mesh = g.mesh(target_elements=50_000)      # an element budget

Surface meshes

g.surface_mesh() meshes only the surfaces (interfaces, outer boundary, sheets) and gives its edge topology and the same sets and file output. rm.polygon_union merges overlapping layout polygons into outlines for sheets and prisms.

What happened, how long, and where the quality is worst

print(mesh.report())     # stage timings, quality with location, warnings
mesh.timings             # seconds per stage
mesh.metrics             # predicate counts, point and tet counts
mesh.quality             # min_dihedral_deg, worst_location, worst_region, regions
mesh.diagnostics         # histogram, watertightness, fidelity, located defects
mesh.log                 # [{level, stage, message, at}, ...]

Set RAPIDMESH_LOG=1 to stream the log to stderr while meshing.

A geometry the mesher cannot mesh raises rm.MeshError (a ValueError) whose message says where and what to repair: features far below the mesh size, gaps between solids, degenerate faces.

License

Dual licensed: GNU Affero General Public License v3.0, or a commercial license for use in proprietary products and services without the AGPL obligations (contact milanrother.com/consulting). Versions up to 0.6.0 were published under the MIT license.