EMS Mesh Checker

ems_mesh_checker is a Python proof-of-concept for checking finite-element mesh topology and reconstructing representative Property geometry from EMSolution meshes. It uses PyVista/VTK for feature-edge extraction, then applies its own topology and curve reconstruction to export reusable CAD/mesher input.

Features

• Extract external faces and interfaces between Property IDs.
• Select only specified Properties with --properties.
• Exclude specified Properties, such as an air region, with --exclude-properties.
• Treat multiple Properties as one region and omit their mutual interfaces with --merge-properties.
• Optionally suppress same-Property hexahedron/tetrahedron coupling interfaces made from one quadrilateral and two triangles.
• Reconstruct representative straight lines and circular arcs from feature edges.
• Export the same reconstructed curves to DXF, Gmsh GEO, and Femap Neutral geometry files.
• Report node/element loading progress for large Femap Neutral files.

The current PoC targets linear elements. Higher-order element support is not a current release goal.

Installation

Python 3.10 or newer is required. The normal installation model is to install both projects as Python packages; the two repositories do not need to remain in the same parent directory.

Install from PyPI. ems-file-format-converter 0.6.0 or newer is installed automatically as a dependency:

python -m pip install ems-mesh-checker

For development of both projects, clone and install both repositories:

git clone https://github.com/EMSolution-SSIL/ems_file_format_converter.git
git clone https://github.com/EMSolution-SSIL/ems_mesh_checker.git

python -m venv .venv
.\.venv\Scripts\python.exe -m pip install -e .\ems_file_format_converter
.\.venv\Scripts\python.exe -m pip install -e ".\ems_mesh_checker[dev]"

The editable installs may point to repositories in any directories. Placing them next to each other is only a convenient convention.

Command-line usage

The command accepts an arbitrary input mesh. It always writes three files with the same stem: representative .dxf, .geo, and Femap geometry .neu.

ems-mesh-checker INPUT_MESH [OUTPUT.dxf]

IronCoil public sample:

ems-mesh-checker .\data\3D\IronCoil\post_geom.atl .\generated\IronCoil.dxf `
  --circle-elements-per-turn 48

QuadTri public sample, retaining cross-Property boundaries while suppressing same-Property hex/tet coupling faces:

ems-mesh-checker .\data\3D\QuadTri\post_geom.neu .\generated\QuadTri.dxf `
  --suppress-quad-tri-interfaces

Export only Properties 2 and 5:

ems-mesh-checker model.neu geometry.dxf --properties 2,5

Exclude air Property 1 and merge Properties 4 and 5 into one extracted region:

ems-mesh-checker model.neu geometry.dxf `
  --exclude-properties 1 `
  --merge-properties 4,5

For repeated independent groups, repeat --merge-properties. Run ems-mesh-checker --help for tolerance, preview, Gmsh validation, and other options.

PyVista can occasionally return small triangular or polygonal feature-edge noise. The opt-in cleanup below removes closed edge loops and isolated open surface components whose boundary contains at most 10 edges; adjust --max-loop-edges for the model when needed.

ems-mesh-checker model.neu geometry.dxf `
  --remove-small-loops `
  --max-loop-edges 10

This cleanup is disabled by default because a small loop or open surface can also be a real geometric feature. Closed and multi-surface components are kept, as are 2-D closed regions. The CLI reports both removed edge loops and removed open surface components in its diagnostics.

Output formats

• DXF contains point/line/arc-oriented representative geometry for CAD and mesher interoperability.
• Gmsh GEO contains points, lines, circles, planar/ruled surfaces, surface loops, and volumes where reconstruction succeeds.
• Femap Neutral output contains reconstructed point, line, and arc geometry.

Feature-edge extraction is heuristic. Complex or noisy meshes may contain open shells or unsupported planar regions; review the CLI diagnostics and generated geometry before using it for production meshing.

Python API

The lower-level API is available from ems_mesh_checker:

from ems_file_format_converter import read_mesh
from ems_mesh_checker import BoundaryExtractor, FeatureEdgeConfig
from ems_mesh_checker import extract_property_group_feature_edges

mesh = read_mesh("model.neu", progress=True)
boundaries = BoundaryExtractor(mesh).extract()
features = extract_property_group_feature_edges(
    boundaries,
    (2, 5),
    config=FeatureEdgeConfig(
        feature_angle_degrees=30.0,
        remove_small_loops=True,
        max_loop_edges=10,
    ),
)

Public sample data

Only the following reviewed sample models are included:

• data/3D/IronCoil/post_geom.atl
• data/3D/QuadTri/post_geom.neu

Other development and customer models are intentionally excluded. The .gitignore treats all additional files below data/ as private by default.

Tests

python -m pytest -q

License

MIT License. Copyright (c) 2026 Hiroyuki Kaimori. See LICENSE.