smesh/doc/salome/gui/SMESH/constructing_meshes.htm

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<h1>Creating Meshes</h1>

<p class="whs1">First of all see <a href="smesh.py_introduction.htm">Example 
 of 3d mesh generation</a>, which is an example of good python script style 
 for Mesh module. </p>

<p class="whs1">Other examples of python 
 scripts will be also updated soon to use smesh package instead of direct 
 usage of idl interface. </p>

<h3><a name=bookmark>Construction of a Mesh</a></h3>

<p class="whs2"><span style="font-family: 'Lucida Console', monospace;">import 
 geompy</span></p>

<p class="whs2">import smesh</p>

<p class="whs2">&nbsp;</p>

<p class="whs3"># create a box</p>

<p class="whs2">box = geompy.MakeBox(0., 
 0., 0., 100., 200., 300.)</p>

<p class="whs2">idbox = geompy.addToStudy(box, 
 &quot;box&quot;)</p>

<p class="whs2">&nbsp;</p>

<p class="whs3"># create a mesh</p>

<p class="whs2">tetra = smesh.Mesh(box, 
 &quot;MeshBox&quot;)</p>

<p class="whs2">&nbsp;</p>

<p class="whs2">algo1D = tetra.Segment()</p>

<p class="whs2">algo1D.NumberOfSegments(7)</p>

<p class="whs2">&nbsp;</p>

<p class="whs2">algo2D = tetra.Triangle()</p>

<p class="whs2">algo2D.MaxElementArea(800.)</p>

<p class="whs2">&nbsp;</p>

<p class="whs2">algo3D = tetra.Tetrahedron(smesh.NETGEN)</p>

<p class="whs2">algo3D.MaxElementVolume(900.)</p>

<p class="whs2">&nbsp;</p>

<p class="whs3"># compute the mesh</p>

<p class="whs2">ret = tetra.Compute()</p>

<p class="whs2">if ret == 0:</p>

<p class="whs2">&nbsp;&nbsp;&nbsp;&nbsp;print 
 &quot;problem when computing the mesh&quot;</p>

<p class="whs2">else:</p>

<p class="whs2">&nbsp;&nbsp;&nbsp;&nbsp;print 
 &quot;mesh computed&quot;</p>

<p class="whs2">&nbsp;&nbsp;&nbsp;&nbsp;pass 
 </p>

<p class="whs2">&nbsp;</p>

<p class="whs2">&nbsp;</p>

<h3><a name=bookmark1>Construction of a Submesh</a></h3>

<p class="whs4"><span style="font-family: 'Lucida Console', monospace;">from 
 geompy import *</span></p>

<p class="whs4">import smesh</p>

<p class="whs4">&nbsp;</p>

<p class="whs5"># create a box</p>

<p class="whs4">box = MakeBoxDXDYDZ(10., 10., 10.)</p>

<p class="whs4">addToStudy(box, &quot;Box&quot;)</p>

<p class="whs4">&nbsp;</p>

<p class="whs5"># select one edge of 
 the box for definition of a local hypothesis</p>

<p class="whs4">p5 = MakeVertex(5., 0., 0.)</p>

<p class="whs4">EdgeX = GetEdgeNearPoint(box, p5)</p>

<p class="whs4">addToStudyInFather(box, EdgeX, &quot;Edge 
 [0,0,0 - 10,0,0]&quot;)</p>

<p class="whs4">&nbsp;</p>

<p class="whs5"># create a hexahedral 
 mesh on the box</p>

<p class="whs4">quadra = smesh.Mesh(box, &quot;Box : quadrangle 
 2D mesh&quot;)</p>

<p class="whs4">&nbsp;</p>

<p class="whs5"># create a regular 
 1D algorithm for the faces</p>

<p class="whs4">algo1D = quadra.Segment()</p>

<p class="whs4">&nbsp;</p>

<p class="whs5"># define &quot;NumberOfSegments&quot; 
 hypothesis to cut</p>

<p class="whs5"># all the edges in 
 a fixed number of segments</p>

<p class="whs4">algo1D.NumberOfSegments(4)</p>

<p class="whs4">&nbsp;</p>

<p class="whs5"># create a quadrangle 
 2D algorithm for the faces</p>

<p class="whs4">quadra.Quadrangle()</p>

<p class="whs4">&nbsp;</p>

<p class="whs5"># construct a submesh 
 on the edge with a local hypothesis</p>

<p class="whs4">algo_local = quadra.Segment(EdgeX)</p>

<p class="whs4">&nbsp;</p>

<p class="whs5"># define &quot;Arithmetic1D&quot; 
 hypothesis to cut the edge<span style="margin-top: 0px;
										margin-bottom: 0px;
										font-family: 'Times New Roman', serif;"> 
 in several segments with increasing arithmetic length</span></p>

<p class="whs4">algo_local.Arithmetic1D(1, 4)</p>

<p class="whs4">&nbsp;</p>

<p class="whs5"># define &quot;Propagation&quot; 
 hypothesis that propagates all other hypotheses</p>

<p class="whs5"># on all edges of the 
 opposite side in case of quadrangular faces</p>

<p class="whs4">algo_local.Propagation()</p>

<p class="whs4">&nbsp;</p>

<p class="whs5"># compute the mesh</p>

<p class="whs4">quadra.Compute() </p>

<p class="whs4">&nbsp;</p>

<h3><a name=bookmark2>Editing of a mesh</a></h3>

<p class="whs4"><span style="font-family: 'Lucida Console', monospace;">import 
 geompy</span></p>

<p class="whs4">import smesh</p>

<p class="whs4">&nbsp;</p>

<p class="whs4">def PrintMeshInfo(theMesh):</p>

<p class="whs4">&nbsp;&nbsp;&nbsp;&nbsp;aMesh 
 = theMesh.GetMesh()</p>

<p class="whs4">&nbsp;&nbsp;&nbsp;&nbsp;print 
 &quot;Information about mesh:&quot;</p>

<p class="whs4">&nbsp;&nbsp;&nbsp;&nbsp;print 
 &quot;Number of nodes &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;: 
 &quot;, aMesh.NbNodes()</p>

<p class="whs4">&nbsp;&nbsp;&nbsp;&nbsp;print 
 &quot;Number of edges &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;: 
 &quot;, aMesh.NbEdges()</p>

<p class="whs4">&nbsp;&nbsp;&nbsp;&nbsp;print 
 &quot;Number of faces &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;: 
 &quot;, aMesh.NbFaces()</p>

<p class="whs4">&nbsp;&nbsp;&nbsp;&nbsp;print 
 &quot;Number of volumes &nbsp;&nbsp;&nbsp;&nbsp;: 
 &quot;, aMesh.NbVolumes()</p>

<p class="whs4">&nbsp;&nbsp;&nbsp;&nbsp;pass</p>

<p class="whs4">&nbsp;</p>

<p class="whs5"># create a box</p>

<p class="whs4">box = geompy.MakeBox(0., 0., 0., 20., 
 20., 20.)</p>

<p class="whs4">geompy.addToStudy(box, &quot;box&quot;)</p>

<p class="whs4">&nbsp;</p>

<p class="whs5"># select one edge of 
 the box for definition of a local hypothesis</p>

<p class="whs4">subShapeList = geompy.SubShapeAll(box, 
 geompy.ShapeType[&quot;EDGE&quot;])</p>

<p class="whs4">edge = subShapeList[0]</p>

<p class="whs4">name = geompy.SubShapeName(edge, box)</p>

<p class="whs4">geompy.addToStudyInFather(box, edge, name)</p>

<p class="whs4">&nbsp;</p>

<p class="whs5"># create a mesh</p>

<p class="whs4">tria = smesh.Mesh(box, &quot;Mesh 2D&quot;)</p>

<p class="whs4">algo1D = tria.Segment()</p>

<p class="whs4">hyp1 = algo1D.NumberOfSegments(3)</p>

<p class="whs4">algo2D = tria.Triangle()</p>

<p class="whs4">hyp2 = algo2D.MaxElementArea(10.)</p>

<p class="whs4">&nbsp;</p>

<p class="whs5"># create a sub-mesh</p>

<p class="whs4">algo_local = tria.Segment(edge)</p>

<p class="whs4">hyp3 = algo_local.Arithmetic1D(1, 6)</p>

<p class="whs4">hyp4 = algo_local.Propagation()</p>

<p class="whs4">&nbsp;</p>

<p class="whs5"># compute the mesh</p>

<p class="whs4">tria.Compute()</p>

<p class="whs4">PrintMeshInfo(tria)</p>

<p class="whs4">&nbsp;</p>

<p class="whs5"># remove a local hypothesis</p>

<p class="whs4">mesh = tria.GetMesh()</p>

<p class="whs4">mesh.RemoveHypothesis(edge, hyp4)</p>

<p class="whs4">&nbsp;</p>

<p class="whs5"># compute the mesh</p>

<p class="whs4">tria.Compute()</p>

<p class="whs4">PrintMeshInfo(tria)</p>

<p class="whs4">&nbsp;</p>

<p class="whs5"># change the value 
 of the 2D hypothesis</p>

<p class="whs4">hyp2.SetMaxElementArea(2.)</p>

<p class="whs4">&nbsp;</p>

<p class="whs5"># compute the mesh</p>

<p class="whs4">tria.Compute()</p>

<p class="whs4">PrintMeshInfo(tria) </p>

<p class="whs6">&nbsp;</p>

<h3><a name=bookmark3>Export of a Mesh</a></h3>

<p class="whs7">import geompy</p>

<p class="whs7">import smesh</p>

<p class="whs6">&nbsp;</p>

<p class="whs6"># create a box</p>

<p class="whs7">box = geompy.MakeBox(0., 
 0., 0., 100., 200., 300.)</p>

<p class="whs7">idbox = geompy.addToStudy(box, 
 &quot;box&quot;)</p>

<p class="whs6">&nbsp;</p>

<p class="whs6"># create a mesh</p>

<p class="whs7">tetra = smesh.Mesh(box, 
 &quot;MeshBox&quot;)</p>

<p class="whs6">&nbsp;</p>

<p class="whs7">algo1D = tetra.Segment()</p>

<p class="whs7">algo1D.NumberOfSegments(7)</p>

<p class="whs7">&nbsp;</p>

<p class="whs7">algo2D = tetra.Triangle()</p>

<p class="whs7">algo2D.MaxElementArea(800.)</p>

<p class="whs7">&nbsp;</p>

<p class="whs7">algo3D = tetra.Tetrahedron(smesh.NETGEN)</p>

<p class="whs7">algo3D.MaxElementVolume(900.)</p>

<p class="whs6">&nbsp;</p>

<p class="whs6"># compute the mesh</p>

<p class="whs7">tetra.Compute()</p>

<p class="whs6">&nbsp;</p>

<p class="whs6"># export the mesh in a 
 MED file</p>

<p class="whs7">tetra.ExportMED(&quot;/tmp/meshMED.med&quot;, 
 0) </p>

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