The Gmsh API Cookbook

This is a collection of short examples to get you started with the Gmsh API.

Geometry

Mesh

Post processing

Gmsh is copyright (C) Christophe Geuzaine and Jean-François Remacle

Geometry

Embed a point in a curve

Gmsh supports embedding arbitrary points in surfaces and volumes, but not for curves.

We can provide this feature ourselves by segmenting the curve at the given point. This requires the OpenCASCADE kernel.

Python

import gmsh

def pointInCurve(point_tag, curve_tag):
    return gmsh.model.occ.fragment([(0, point_tag)], [(1, curve_tag)])[0]

gmsh.initialize()
a = gmsh.model.occ.addPoint(0, 0, 0)
b = gmsh.model.occ.addPoint(5, 0, 0)
line = gmsh.model.occ.addLine(a, b)

# the point we want to embed
p = gmsh.model.occ.addPoint(1, 0, 0)

# embed it
result_tags = pointInCurve(p, line)
# find the new point tag
embedded_point = next(tag for (dim, tag) in result_tags if dim == 0)

# add a physical group for the new point
gmsh.model.occ.synchronize()
group = gmsh.model.addPhysicalGroup(0, [embedded_point])
gmsh.model.setPhysicalName(0, group, "embedded point")

gmsh.finalize()

Mesh

Line segments

Gmsh does not have a line segment primitive, but we can make our own by adding 1D mesh elements one by one.

Python

import gmsh
import itertools

# points to connect
points = [(-1, 0, 0), (1, 1, 0), (-1, 2, 0), (1, 3, 0), (-1, 4, 0)]

# assign node numbers
nodes = [x for x in range(1, len(points)+1)]
# get a flat list of coordinates
coords = list(itertools.chain.from_iterable(points))

gmsh.initialize()
# add a dummy line to add nodes to
dummy_line = 1
gmsh.model.addDiscreteEntity(1, dummy_line)

# add nodes
gmsh.model.mesh.addNodes(1, dummy_line, nodes, coords)

# add line elements between each node
line_elt = 1
for i in range(len(nodes) - 1):
    gmsh.model.mesh.addElementsByType(
        dummy_line, line_elt, [], [nodes[i], nodes[i+1]])

gmsh.finalize()

Post processing

List of view names

A lot of Gmsh state is available through the options interface. We use this feature to get a list of all the view names.

Python

import gmsh

def getViewNames(view_tags):
        return [gmsh.option.getString(f'View[{gmsh.view.getIndex(tag)}].Name')
                for tag in view_tags]

gmsh.initialize()

gmsh.view.add("view 1")
gmsh.view.add("view 2")
gmsh.view.add("view 3")

for name in getViewNames(gmsh.view.getTags()):
    print(name)

gmsh.finalize()