smesh/doc/salome/gui/SMESH/input/tui_creating_meshes.doc

/*!

\page tui_creating_meshes_page Creating Meshes

\n First of all see \ref example_3d_mesh "Example of 3d mesh generation",
 which is an example of good python script style for Mesh module.

<br>
<h2>Construction of a Mesh</h2>

\code
import geompy
import smesh

# create a box
box = geompy.MakeBox(0., 0., 0., 100., 200., 300.)
idbox = geompy.addToStudy(box, "box")

# create a mesh
tetra = smesh.Mesh(box, "MeshBox")

algo1D = tetra.Segment()
algo1D.NumberOfSegments(7)

algo2D = tetra.Triangle()
algo2D.MaxElementArea(800.)

algo3D = tetra.Tetrahedron(smesh.NETGEN)
algo3D.MaxElementVolume(900.)

# compute the mesh
ret = tetra.Compute()
if ret == 0:
    print "problem when computing the mesh"
else:
    print "mesh computed"
    pass
\endcode

<br>
\anchor tui_construction_submesh
<h2>Construction of a Submesh</h2>

\code
from geompy import *
import smesh

# create a box
box = MakeBoxDXDYDZ(10., 10., 10.)
addToStudy(box, "Box")

# select one edge of the box for definition of a local hypothesis
p5 = MakeVertex(5., 0., 0.)
EdgeX = GetEdgeNearPoint(box, p5)
addToStudyInFather(box, EdgeX, "Edge [0,0,0 - 10,0,0]")

# create a hexahedral mesh on the box
quadra = smesh.Mesh(box, "Box : quadrangle 2D mesh")

# create a regular 1D algorithm for the faces
algo1D = quadra.Segment()

# define "NumberOfSegments" hypothesis to cut
# all the edges in a fixed number of segments
algo1D.NumberOfSegments(4)

# create a quadrangle 2D algorithm for the faces
quadra.Quadrangle()

# construct a submesh on the edge with a local hypothesis
algo_local = quadra.Segment(EdgeX)

# define "Arithmetic1D" hypothesis to cut the edge in several segments with increasing arithmetic length
algo_local.Arithmetic1D(1, 4)

# define "Propagation" hypothesis that propagates all other hypotheses
# on all edges of the opposite side in case of quadrangular faces
algo_local.Propagation()

# compute the mesh
quadra.Compute()

\endcode

<br>
<h2>Change priority of submeshes in Mesh</h2>

\code
import salome
import geompy
import smesh
import SMESH

Box_1 = geompy.MakeBoxDXDYDZ(200, 200, 200)
[Face_1,Face_2,Face_3,Face_4,Face_5,Face_6] = geompy.SubShapeAllSorted(Box_1, geompy.ShapeType["FACE"])

# create Mesh object on Box shape
Mesh_1 = smesh.Mesh(Box_1)

# assign mesh algorithms
Regular_1D = Mesh_1.Segment()
Nb_Segments_1 = Regular_1D.NumberOfSegments(20)
Nb_Segments_1.SetDistrType( 0 )
MEFISTO_2D = Mesh_1.Triangle()
Max_Element_Area_1 = MEFISTO_2D.MaxElementArea(1200)
Tetrahedron_Netgen = Mesh_1.Tetrahedron(algo=smesh.NETGEN)
Max_Element_Volume_1 = Tetrahedron_Netgen.MaxElementVolume(40000)

# create submesh and assign algorithms on Face_1
Netgen_1D_2D = Mesh_1.Triangle(algo=smesh.NETGEN,geom=Face_1)
SubMesh_1 = Netgen_1D_2D.GetSubMesh()
NETGEN_2D_Simple_Parameters_1 = Netgen_1D_2D.Parameters(which=smesh.SIMPLE)
NETGEN_2D_Simple_Parameters_1.SetNumberOfSegments( 4 )
NETGEN_2D_Simple_Parameters_1.LengthFromEdges()

# create submesh and assign algorithms on Face_2
Netgen_1D_2D_1 = Mesh_1.Triangle(algo=smesh.NETGEN,geom=Face_2)
SubMesh_2 = Netgen_1D_2D_1.GetSubMesh()
NETGEN_2D_Simple_Parameters_2 = Netgen_1D_2D_1.Parameters(which=smesh.SIMPLE)
NETGEN_2D_Simple_Parameters_2.SetNumberOfSegments( 8 )
NETGEN_2D_Simple_Parameters_2.LengthFromEdges()
smeshObj_1 = smesh.CreateHypothesis('NETGEN_SimpleParameters_2D',
'NETGENEngine')

# create submesh and assign algorithms on Face_3
Netgen_1D_2D_2 = Mesh_1.Triangle(algo=smesh.NETGEN,geom=Face_3)
SubMesh_3 = Netgen_1D_2D_2.GetSubMesh()
NETGEN_2D_Simple_Parameters_3 = Netgen_1D_2D_2.Parameters(which=smesh.SIMPLE)
NETGEN_2D_Simple_Parameters_3.SetNumberOfSegments( 12 )
NETGEN_2D_Simple_Parameters_3.LengthFromEdges()

# check exisiting submesh priority order
[ [ SubMesh_1, SubMesh_3, SubMesh_2 ] ] = Mesh_1.GetMeshOrder()
# set new submesh order
isDone = Mesh_1.SetMeshOrder( [ [ SubMesh_1, SubMesh_2, SubMesh_3 ] ])
# compute mesh
isDone = Mesh_1.Compute()

# clear mesh result and compute with other submesh order
Mesh_1.Clear()
isDone = Mesh_1.SetMeshOrder( [ [ SubMesh_2, SubMesh_1, SubMesh_3 ] ])
isDone = Mesh_1.Compute()

\endcode

<br>
\anchor tui_editing_mesh
<h2>Editing of a mesh</h2>

\code
import geompy
import smesh

def PrintMeshInfo(theMesh):
    aMesh = theMesh.GetMesh()
    print "Information about mesh:"
    print "Number of nodes       : ", aMesh.NbNodes()
    print "Number of edges       : ", aMesh.NbEdges()
    print "Number of faces       : ", aMesh.NbFaces()
    print "Number of volumes     : ", aMesh.NbVolumes()
    pass

# create a box
box = geompy.MakeBox(0., 0., 0., 20., 20., 20.)
geompy.addToStudy(box, "box")

# select one edge of the box for definition of a local hypothesis
subShapeList = geompy.SubShapeAll(box, geompy.ShapeType["EDGE"])
edge = subShapeList[0]
name = geompy.SubShapeName(edge, box)
geompy.addToStudyInFather(box, edge, name)

# create a mesh
tria = smesh.Mesh(box, "Mesh 2D")
algo1D = tria.Segment()
hyp1 = algo1D.NumberOfSegments(3)
algo2D = tria.Triangle()
hyp2 = algo2D.MaxElementArea(10.)

# create a sub-mesh
algo_local = tria.Segment(edge)
hyp3 = algo_local.Arithmetic1D(1, 6)
hyp4 = algo_local.Propagation()

# compute the mesh
tria.Compute()
PrintMeshInfo(tria)

# remove a local hypothesis
mesh = tria.GetMesh()
mesh.RemoveHypothesis(edge, hyp4)

# compute the mesh
tria.Compute()
PrintMeshInfo(tria)

# change the value of the 2D hypothesis
hyp2.SetMaxElementArea(2.)

# compute the mesh
tria.Compute()
PrintMeshInfo(tria)
\endcode

<br>
\anchor tui_export_mesh
<h2>Export of a Mesh</h2>

\code
import geompy
import smesh

# create a box
box = geompy.MakeBox(0., 0., 0., 100., 200., 300.)
idbox = geompy.addToStudy(box, "box")

# create a mesh
tetra = smesh.Mesh(box, "MeshBox")

algo1D = tetra.Segment()
algo1D.NumberOfSegments(7)

algo2D = tetra.Triangle()
algo2D.MaxElementArea(800.)

algo3D = tetra.Tetrahedron(smesh.NETGEN)
algo3D.MaxElementVolume(900.)

# compute the mesh
tetra.Compute()

# export the mesh in a MED file
tetra.ExportMED("/tmp/meshMED.med", 0)

# export a group in a MED file
face = geompy.SubShapeAll( box, geompy.ShapeType["FACE"])[0] # a box side
group = tetra.GroupOnGeom( face, "face group" ) # group of 2D elements on the <face>
tetra.ExportMED("/tmp/groupMED.med", meshPart=group)
\endcode

<br>
<h2>How to mesh a cylinder with hexahedrons?</h2>
Here you can see an example of python script, creating a hexahedral
mesh on a cylinder. And a picture below the source code of the script,
demonstrating the resulting mesh.
\include ex24_cylinder.py

\image html mesh_cylinder_hexa.png

<br>
\anchor tui_building_compound
<h2>Building a compound of meshes</h2>
\dontinclude SMESH_BuildCompound.py
\skipline import geompy
\until #end

<br>
\anchor tui_copy_mesh
<h2>Mesh Copying</h2>
\code
from smesh import *
SetCurrentStudy(salome.myStudy)

# make geometry of a box
box = geompy.MakeBoxDXDYDZ(100,100,100)
face = geompy.SubShapeAllSorted(box, geompy.ShapeType["FACE"])[0]

# generate 3D mesh
mesh = Mesh(box)
localAlgo = mesh.Triangle(face)
mesh.AutomaticHexahedralization()

# objects to copy
fGroup = mesh.GroupOnGeom( face, "2D on face")
nGroup = mesh.GroupOnGeom( face, "nodes on face", NODE)
subMesh = localAlgo.GetSubMesh()

# make a new mesh by copying different parts of the mesh

# 1. copy the whole mesh
newMesh = CopyMesh( mesh, "whole mesh copy")

# 2. copy a group of 2D elements along with groups
newMesh = CopyMesh( fGroup,  "face group copy with groups",toCopyGroups=True)

# 3. copy a group of nodes with preseving their ids
newMesh = CopyMesh( nGroup, "node group copy", toKeepIDs=True)

# 4. copy some faces
faceIds = fGroup.GetIDs()[-10:]
newMesh = CopyMesh( mesh.GetIDSource( faceIds, FACE ), "some faces copy")

# 5. copy some nodes
nodeIds = nGroup.GetIDs()[-10:]
newMesh = CopyMesh( mesh.GetIDSource( nodeIds, NODE), "some nodes copy")

# 6. copy a sub-mesh
newMesh = CopyMesh( subMesh, "submesh copy" )
\endcode

*/