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Giannis Nikiteas authoredGiannis Nikiteas authored
t3.py 5.34 KiB
# ------------------------------------------------------------------------------
#
# Gmsh Python tutorial 3
#
# Extruded meshes, ONELAB parameters, options
#
# ------------------------------------------------------------------------------
import gmsh
import math
import sys
gmsh.initialize()
def createGeometryAndMesh():
# Clear all models and create a new one
gmsh.clear()
gmsh.model.add("t3")
# Copied from t1.py...
lc = 1e-2
gmsh.model.geo.addPoint(0, 0, 0, lc, 1)
gmsh.model.geo.addPoint(.1, 0, 0, lc, 2)
gmsh.model.geo.addPoint(.1, .3, 0, lc, 3)
gmsh.model.geo.addPoint(0, .3, 0, lc, 4)
gmsh.model.geo.addLine(1, 2, 1)
gmsh.model.geo.addLine(3, 2, 2)
gmsh.model.geo.addLine(3, 4, 3)
gmsh.model.geo.addLine(4, 1, 4)
gmsh.model.geo.addCurveLoop([4, 1, -2, 3], 1)
gmsh.model.geo.addPlaneSurface([1], 1)
gmsh.model.geo.synchronize()
gmsh.model.addPhysicalGroup(1, [1, 2, 4], 5)
ps = gmsh.model.addPhysicalGroup(2, [1])
gmsh.model.setPhysicalName(2, ps, "My surface")
# As in `t2.py', we plan to perform an extrusion along the z axis. But
# here, instead of only extruding the geometry, we also want to extrude the
# 2D mesh. This is done with the same `extrude()' function, but by
# specifying element 'Layers' (2 layers in this case, the first one with 8
# subdivisions and the second one with 2 subdivisions, both with a height of
# h/2). The number of elements for each layer and the (end) height of each
# layer are specified in two vectors:
h = 0.1
ov = gmsh.model.geo.extrude([(2, 1)], 0, 0, h, [8, 2], [0.5, 1])
# The extrusion can also be performed with a rotation instead of a
# translation, and the resulting mesh can be recombined into prisms (we use
# only one layer here, with 7 subdivisions). All rotations are specified by
# an an axis point (-0.1, 0, 0.1), an axis direction (0, 1, 0), and a
# rotation angle (-Pi/2):
ov = gmsh.model.geo.revolve([(2, 28)], -0.1, 0, 0.1, 0, 1, 0, -math.pi / 2,
[7])
# Using the built-in geometry kernel, only rotations with angles < Pi are
# supported. To do a full turn, you will thus need to apply at least 3
# rotations. The OpenCASCADE geometry kernel does not have this limitation.
# A translation (-2 * h, 0, 0) and a rotation ((0, 0.15, 0.25), (1, 0, 0),
# angle * Pi / 180) can also be combined to form a "twist". The last
# (optional) argument for the extrude() and twist() functions specifies
# whether the extruded mesh should be recombined or not. The `angle'
# parameter is retrieved from the ONELAB database (it can be set
# interactively in the GUI -- see below):
angle = gmsh.onelab.getNumber('Parameters/Twisting angle')[0]
ov = gmsh.model.geo.twist([(2, 50)], 0, 0.15, 0.25, -2 * h, 0, 0, 1, 0, 0,
angle * math.pi / 180., [10], [], True)
gmsh.model.geo.synchronize()
# All the extrusion functions return a vector of extruded entities: the
# "top" of the extruded surface (in `ov[0]'), the newly created volume (in
# `ov[1]') and the tags of the lateral surfaces (in `ov[2]', `ov[3]', ...).
# We can then define a new physical volume (with tag 101) to group all the
# elementary volumes:
gmsh.model.addPhysicalGroup(3, [1, 2, ov[1][1]], 101)
gmsh.model.mesh.generate(3)
gmsh.write("t3.msh")
# Let us now change some options... Since all interactive options are accessible
# through the API, we can for example make point tags visible or redefine some
# colors:
gmsh.option.setNumber("Geometry.PointNumbers", 1)
gmsh.option.setColor("Geometry.Points", 255, 165, 0)
gmsh.option.setColor("General.Text", 255, 255, 255)
gmsh.option.setColor("Mesh.Points", 255, 0, 0)
# Note that color options are special: setting a color option of "X.Y"
# actually sets the option "X.Color.Y".
r, g, b, a = gmsh.option.getColor("Geometry.Points")
gmsh.option.setColor("Geometry.Surfaces", r, g, b, a)
# We create a ONELAB parameter to define the angle of the twist. ONELAB
# parameters can be modified interactively in the GUI, and can be exchanged with
# other codes connected to the same ONELAB database. The database can be
# accessed through the Gmsh Python API using JSON-formatted strings (see
# https://gitlab.onelab.info/doc/tutorials/-/wikis/ONELAB-JSON-interface for
# more information):
gmsh.onelab.set("""[
{
"type":"number",
"name":"Parameters/Twisting angle",
"values":[90],
"min":0,
"max":120,
"step":1
}
]""")
# Create the geometry and mesh it:
createGeometryAndMesh()
# Launch the GUI and handle the "check" event (recorded in the "ONELAB/Action"
# parameter) to recreate the geometry with a new twisting angle if necessary:
def checkForEvent():
action = gmsh.onelab.getString("ONELAB/Action")
if len(action) and action[0] == "check":
gmsh.onelab.setString("ONELAB/Action", [""])
createGeometryAndMesh()
gmsh.graphics.draw()
return True
if "-nopopup" not in sys.argv:
gmsh.fltk.initialize()
while gmsh.fltk.isAvailable() and checkForEvent():
gmsh.fltk.wait()
# When the GUI is launched, you can use the `Help->Current Options and
# Workspace' menu to see the current values of all options. To save the options
# in a file, use `File->Export->Gmsh Options', or through the api:
# gmsh.write("t3.opt");
gmsh.finalize()