<!doctype HTML public "-//W3C//DTD HTML 4.0 Frameset//EN"> <html> <head> <title>Constructing Meshes</title> <meta http-equiv="content-type" content="text/html; charset=windows-1252"> <meta name="generator" content="RoboHelp by eHelp Corporation www.ehelp.com"><style type="text/css"> <!-- p.whs1 { margin-top:0pt; margin-bottom:0pt; } p.whs2 { margin-top:0pt; margin-bottom:0pt; font-family:'Lucida Console' , monospace; } p.whs3 { margin-top:0pt; margin-bottom:0pt; font-family:'Times New Roman' , serif; } p.whs4 { font-family:'Lucida Console' , monospace; margin-top:0px; margin-bottom:0px; } p.whs5 { margin-top:0px; margin-bottom:0px; font-family:'Times New Roman' , serif; } p.whs6 { margin-top:0px; margin-bottom:0px; } p.whs7 { margin-top:0px; margin-bottom:0px; font-family:'Lucida Console' , monospace; } --> </style><script type="text/javascript" language="JavaScript"> <!-- if ((navigator.appName == "Netscape") && (parseInt(navigator.appVersion) == 4)) { var strNSS = "<style type='text/css'>"; 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addButton("show",BTN_IMG,"Show","","","","",0,0,"whd_show0.gif","whd_show2.gif","whd_show1.gif"); addButton("hide",BTN_IMG,"Hide","","","","",0,0,"whd_hide0.gif","whd_hide2.gif","whd_hide1.gif"); } if (window.setRelStartPage) { setRelStartPage("index.htm"); autoSync(1); sendSyncInfo(); sendAveInfoOut(); } } else if (window.gbIE4) document.location.reload(); //--> </script> </head> <body><script type="text/javascript" language="javascript1.2"> <!-- if (window.writeIntopicBar) writeIntopicBar(4); //--> </script> <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"> </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, "box")</p> <p class="whs2"> </p> <p class="whs3"># create a mesh</p> <p class="whs2">tetra = smesh.Mesh(box, "MeshBox")</p> <p class="whs2"> </p> <p class="whs2">algo1D = tetra.Segment()</p> <p class="whs2">algo1D.NumberOfSegments(7)</p> <p class="whs2"> </p> <p class="whs2">algo2D = tetra.Triangle()</p> <p class="whs2">algo2D.MaxElementArea(800.)</p> <p class="whs2"> </p> <p class="whs2">algo3D = tetra.Tetrahedron(smesh.NETGEN)</p> <p class="whs2">algo3D.MaxElementVolume(900.)</p> <p class="whs2"> </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"> print "problem when computing the mesh"</p> <p class="whs2">else:</p> <p class="whs2"> print "mesh computed"</p> <p class="whs2"> pass </p> <p class="whs2"> </p> <p class="whs2"> </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"> </p> <p class="whs5"># create a box</p> <p class="whs4">box = MakeBoxDXDYDZ(10., 10., 10.)</p> <p class="whs4">addToStudy(box, "Box")</p> <p class="whs4"> </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, "Edge [0,0,0 - 10,0,0]")</p> <p class="whs4"> </p> <p class="whs5"># create a hexahedral mesh on the box</p> <p class="whs4">quadra = smesh.Mesh(box, "Box : quadrangle 2D mesh")</p> <p class="whs4"> </p> <p class="whs5"># create a regular 1D algorithm for the faces</p> <p class="whs4">algo1D = quadra.Segment()</p> <p class="whs4"> </p> <p class="whs5"># define "NumberOfSegments" 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"> </p> <p class="whs5"># create a quadrangle 2D algorithm for the faces</p> <p class="whs4">quadra.Quadrangle()</p> <p class="whs4"> </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"> </p> <p class="whs5"># define "Arithmetic1D" 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"> </p> <p class="whs5"># define "Propagation" 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"> </p> <p class="whs5"># compute the mesh</p> <p class="whs4">quadra.Compute() </p> <p class="whs4"> </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"> </p> <p class="whs4">def PrintMeshInfo(theMesh):</p> <p class="whs4"> aMesh = theMesh.GetMesh()</p> <p class="whs4"> print "Information about mesh:"</p> <p class="whs4"> print "Number of nodes : ", aMesh.NbNodes()</p> <p class="whs4"> print "Number of edges : ", aMesh.NbEdges()</p> <p class="whs4"> print "Number of faces : ", aMesh.NbFaces()</p> <p class="whs4"> print "Number of volumes : ", aMesh.NbVolumes()</p> <p class="whs4"> pass</p> <p class="whs4"> </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, "box")</p> <p class="whs4"> </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["EDGE"])</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"> </p> <p class="whs5"># create a mesh</p> <p class="whs4">tria = smesh.Mesh(box, "Mesh 2D")</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"> </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"> </p> <p class="whs5"># compute the mesh</p> <p class="whs4">tria.Compute()</p> <p class="whs4">PrintMeshInfo(tria)</p> <p class="whs4"> </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"> </p> <p class="whs5"># compute the mesh</p> <p class="whs4">tria.Compute()</p> <p class="whs4">PrintMeshInfo(tria)</p> <p class="whs4"> </p> <p class="whs5"># change the value of the 2D hypothesis</p> <p class="whs4">hyp2.SetMaxElementArea(2.)</p> <p class="whs4"> </p> <p class="whs5"># compute the mesh</p> <p class="whs4">tria.Compute()</p> <p class="whs4">PrintMeshInfo(tria) </p> <p class="whs6"> </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"> </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, "box")</p> <p class="whs6"> </p> <p class="whs6"># create a mesh</p> <p class="whs7">tetra = smesh.Mesh(box, "MeshBox")</p> <p class="whs6"> </p> <p class="whs7">algo1D = tetra.Segment()</p> <p class="whs7">algo1D.NumberOfSegments(7)</p> <p class="whs7"> </p> <p class="whs7">algo2D = tetra.Triangle()</p> <p class="whs7">algo2D.MaxElementArea(800.)</p> <p class="whs7"> </p> <p class="whs7">algo3D = tetra.Tetrahedron(smesh.NETGEN)</p> <p class="whs7">algo3D.MaxElementVolume(900.)</p> <p class="whs6"> </p> <p class="whs6"># compute the mesh</p> <p class="whs7">tetra.Compute()</p> <p class="whs6"> </p> <p class="whs6"># export the mesh in a MED file</p> <p class="whs7">tetra.ExportMED("/tmp/meshMED.med", 0) </p> <script type="text/javascript" language="javascript1.2"> <!-- if (window.writeIntopicBar) writeIntopicBar(0); 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