Import a mesh

A mesh can be loaded from an external file instead of being generated from geometry. All import paths return a Mesh that can be used directly in any _Simu. Import utilities are available in the Mesher class and in the EasyFEA.Utilities.MeshIO namespace.

When a mesh file contains physical groups (named regions, boundaries), EasyFEA preserves them as tags. Tags are the primary way to identify node and element sets to apply boundary conditions — see Use tags to apply boundary conditions.

Note

A mesh currently supports only one element group of dimension mesh.dim — the dominant volumetric (or surface) elements. Mixing element types at the same dimension (e.g. TETRA4 and HEXA8 in the same 3D mesh) is not supported. Lower-dimension groups (boundary faces, edges) can coexist and are used for tags and Neumann conditions. Lifting this restriction would require non-trivial changes to the simulation assembly layer.

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From a Gmsh .msh file

Use Mesh_Import_mesh() to load an existing Gmsh mesh file:

from EasyFEA import Display, ElemType
from EasyFEA.FEM import Mesher
from EasyFEA.Geoms import Domain

mesher = Mesher()
mesh = mesher.Mesh_Import_mesh("path/to/mesh.msh")

The coef argument scales node coordinates — useful to convert units (e.g. m to mm):

mesh = mesher.Mesh_Import_mesh("path/to/mesh.msh", coef=1000.0)

Set setPhysicalGroups=True to automatically create physical groups from the Gmsh entities, which lets you retrieve node sets by tag afterwards:

mesh = mesher.Mesh_Import_mesh("path/to/mesh.msh", setPhysicalGroups=True)

After importing, use EasyFEA.Utilities.Display.Plot_Tags() or EasyFEA.Utilities.PyVista.Plot_Tags() to visualize the available tags on the mesh:

Display.Plot_Tags(mesh)

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From a CAD file (.stp / .igs)

Use Mesh_Import_part() to mesh a STEP or IGES file directly:

mesh = mesher.Mesh_Import_part("part.stp", dim=3, meshSize=5.0)

Only triangular (TRI3) or tetrahedral (TETRA4) elements are supported for CAD import. Use refineGeoms to locally refine the mesh around specific geometric regions:

refine = Domain((0, 0, 0), (10, 10, 10), meshSize=1.0)
mesh = mesher.Mesh_Import_part("part.stp", dim=3, meshSize=5.0, refineGeoms=[refine])

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From a meshio-compatible format

Note

The MeshIO module requires the io optional dependency:

pip install EasyFEA[io]

Use Gmsh_to_EasyFEA() after loading with meshio directly, or use the dedicated converters:

from EasyFEA.Utilities import MeshIO

# From a Medit .mesh file
mesh = MeshIO.Medit_to_EasyFEA("path/to/mesh.mesh")

# From a Gmsh .msh file (alternative to Mesher.Mesh_Import_mesh)
mesh = MeshIO.Gmsh_to_EasyFEA("path/to/mesh.msh")

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From PyVista

Use PyVista_to_EasyFEA() to convert a PyVista UnstructuredGrid or MultiBlock:

import pyvista as pv
from EasyFEA.Utilities import MeshIO

pv_mesh = pv.read("path/to/mesh.vtk")
mesh = MeshIO.PyVista_to_EasyFEA(pv_mesh)

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From an Ensight file

from EasyFEA.Utilities import MeshIO

mesh = MeshIO.Ensight_to_EasyFEA("path/to/mesh.geo")

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Export a mesh

EasyFEA meshes can also be exported to external formats for use in other tools:

from EasyFEA.Utilities import MeshIO

# To Gmsh .msh
MeshIO.EasyFEA_to_Gmsh(mesh, folder="output/", name="mesh")

# To Medit .mesh
MeshIO.EasyFEA_to_Medit(mesh, folder="output/", name="mesh")

# To Ensight .geo
MeshIO.EasyFEA_to_Ensight(mesh, folder="output/", name="mesh")

# To PyVista UnstructuredGrid
pv_mesh = MeshIO.EasyFEA_to_PyVista(mesh)

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Geometric operations

EasyFEA meshes support in-place geometric transformations directly on the Mesh object:

# Translate by (dx, dy, dz)
mesh.Translate(dx=10.0, dy=0.0, dz=0.0)

# Rotate by theta degrees around an axis
mesh.Rotate(theta=90, center=(0, 0, 0), direction=(0, 0, 1))  # 90° around z-axis

# Symmetry with respect to a plane defined by a point and its normal
mesh.Symmetry(point=(0, 0, 0), n=(1, 0, 0))  # mirror across the y-z plane

All three operations modify the mesh in place and update every element group consistently. They are useful when composing assemblies: transform individual parts before merging them.

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Merge meshes

To combine several meshes into one (e.g. assemblies with multiple parts):

merged = MeshIO.Merge([mesh1, mesh2, mesh3])

Set constructUniqueElements=False to skip deduplication of shared elements if the meshes are already conforming.