wiai / pygmsh

Python interface for Gmsh

pygmsh

Gmsh is a powerful mesh generation tool with a scripting language that is notoriously hard to write.

The goal of pygmsh is to combine the power of Gmsh with the versatility of Python and to provide useful abstractions from the Gmsh scripting language so you can create complex geometries more easily.

See here for the full documentation.

Built-in

To create the above mesh, simply do

import pygmsh
import numpy as np

geom = pygmsh.built_in.Geometry()

# Draw a cross.
poly = geom.add_polygon([
    [ 0.0,  0.5, 0.0],
    [-0.1,  0.1, 0.0],
    [-0.5,  0.0, 0.0],
    [-0.1, -0.1, 0.0],
    [ 0.0, -0.5, 0.0],
    [ 0.1, -0.1, 0.0],
    [ 0.5,  0.0, 0.0],
    [ 0.1,  0.1, 0.0]
    ],
    lcar=0.05
    )

axis = [0, 0, 1]

geom.extrude(
    poly,
    translation_axis=axis,
    rotation_axis=axis,
    point_on_axis=[0, 0, 0],
    angle=2.0 / 6.0 * np.pi
    )

points, cells, point_data, cell_data, field_data = pygmsh.generate_mesh(geom)

to retrieve all points and cells of the mesh for the specified geometry. To store the mesh, you can use meshio; for example

import meshio
meshio.write('test.vtu', points, cells, cell_data=cell_data)

The output file can be visualized with various tools, e.g., ParaView.

You will find the above mesh in the directory test/ along with other small examples.

OpenCASCADE

As of version 3.0, Gmsh supports OpenCASCADE, allowing for a CAD-style geometry specification.

Example:

import pygmsh

geom = pygmsh.opencascade.Geometry(
  characteristic_length_min=0.1,
  characteristic_length_max=0.1,
  )

rectangle = geom.add_rectangle([-1.0, -1.0, 0.0], 2.0, 2.0)
disk1 = geom.add_disk([-1.2, 0.0, 0.0], 0.5)
disk2 = geom.add_disk([+1.2, 0.0, 0.0], 0.5)
union = geom.boolean_union([rectangle, disk1, disk2])

disk3 = geom.add_disk([0.0, -0.9, 0.0], 0.5)
disk4 = geom.add_disk([0.0, +0.9, 0.0], 0.5)
flat = geom.boolean_difference([union], [disk3, disk4])

geom.extrude(flat, [0, 0, 0.3])

points, cells, point_data, cell_data, field_data = pygmsh.generate_mesh(geom)

Installation

pygmsh is available from the Python Package Index, so simply type

pip install -U pygmsh

to install or upgrade.

Usage

Just

import pygmsh as pg

and make use of all the goodies the module provides. The documentation and the examples under test/ might inspire you.

Testing

To run the pygmsh unit tests, check out this repository and type

pytest

Building Documentation

Docs are built using Sphinx.

To build run

sphinx-build -b html doc doc/_build

Distribution

To create a new release

1. bump the __version__ number,

2. publish to PyPi and GitHub:

   $ make publish
   

License

pygmsh is published under the MIT license.