Examples

Built-in Geometry

This is an example showing how to create a mesh of a simple skrew using the built-in geometry module:

To create the above mesh, simply do:

Download file

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 Geometry

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

This is an example showing how to create a mesh of a simple puzzle piece using the OpenCASCADE geometry module:

To create the above mesh, simply do:

Download file

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)