doc/salome/gui/SMESH/constructing_meshes.htm

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  94 <h1>Creating Meshes</h1>
  95
  96 <p class="whs1">First of all see <a href="smesh.py_introduction.htm">Example
  97  of 3d mesh generation</a>, which is an example of good python script style
  98  for Mesh module. </p>
  99
 100 <p class="whs1">Other examples of python
 101  scripts will be also updated soon to use smesh package instead of direct
 102  usage of idl interface. </p>
 103
 104 <h3><a name=bookmark>Construction of a Mesh</a></h3>
 105
 106 <p class="whs2"><span style="font-family: 'Lucida Console', monospace;">import
 107  geompy</span></p>
 108
 109 <p class="whs2">import smesh</p>
 110
 111 <p class="whs2">&nbsp;</p>
 112
 113 <p class="whs3"># create a box</p>
 114
 115 <p class="whs2">box = geompy.MakeBox(0.,
 116  0., 0., 100., 200., 300.)</p>
 117
 118 <p class="whs2">idbox = geompy.addToStudy(box,
 119  &quot;box&quot;)</p>
 120
 121 <p class="whs2">&nbsp;</p>
 122
 123 <p class="whs3"># create a mesh</p>
 124
 125 <p class="whs2">tetra = smesh.Mesh(box,
 126  &quot;MeshBox&quot;)</p>
 127
 128 <p class="whs2">&nbsp;</p>
 129
 130 <p class="whs2">algo1D = tetra.Segment()</p>
 131
 132 <p class="whs2">algo1D.NumberOfSegments(7)</p>
 133
 134 <p class="whs2">&nbsp;</p>
 135
 136 <p class="whs2">algo2D = tetra.Triangle()</p>
 137
 138 <p class="whs2">algo2D.MaxElementArea(800.)</p>
 139
 140 <p class="whs2">&nbsp;</p>
 141
 142 <p class="whs2">algo3D = tetra.Tetrahedron(smesh.NETGEN)</p>
 143
 144 <p class="whs2">algo3D.MaxElementVolume(900.)</p>
 145
 146 <p class="whs2">&nbsp;</p>
 147
 148 <p class="whs3"># compute the mesh</p>
 149
 150 <p class="whs2">ret = tetra.Compute()</p>
 151
 152 <p class="whs2">if ret == 0:</p>
 153
 154 <p class="whs2">&nbsp;&nbsp;&nbsp;&nbsp;print
 155  &quot;problem when computing the mesh&quot;</p>
 156
 157 <p class="whs2">else:</p>
 158
 159 <p class="whs2">&nbsp;&nbsp;&nbsp;&nbsp;print
 160  &quot;mesh computed&quot;</p>
 161
 162 <p class="whs2">&nbsp;&nbsp;&nbsp;&nbsp;pass
 163  </p>
 164
 165 <p class="whs2">&nbsp;</p>
 166
 167 <p class="whs2">&nbsp;</p>
 168
 169 <h3><a name=bookmark1>Construction of a Submesh</a></h3>
 170
 171 <p class="whs4"><span style="font-family: 'Lucida Console', monospace;">from
 172  geompy import *</span></p>
 173
 174 <p class="whs4">import smesh</p>
 175
 176 <p class="whs4">&nbsp;</p>
 177
 178 <p class="whs5"># create a box</p>
 179
 180 <p class="whs4">box = MakeBoxDXDYDZ(10., 10., 10.)</p>
 181
 182 <p class="whs4">addToStudy(box, &quot;Box&quot;)</p>
 183
 184 <p class="whs4">&nbsp;</p>
 185
 186 <p class="whs5"># select one edge of
 187  the box for definition of a local hypothesis</p>
 188
 189 <p class="whs4">p5 = MakeVertex(5., 0., 0.)</p>
 190
 191 <p class="whs4">EdgeX = GetEdgeNearPoint(box, p5)</p>
 192
 193 <p class="whs4">addToStudyInFather(box, EdgeX, &quot;Edge
 194  [0,0,0 - 10,0,0]&quot;)</p>
 195
 196 <p class="whs4">&nbsp;</p>
 197
 198 <p class="whs5"># create a hexahedral
 199  mesh on the box</p>
 200
 201 <p class="whs4">quadra = smesh.Mesh(box, &quot;Box : quadrangle
 202  2D mesh&quot;)</p>
 203
 204 <p class="whs4">&nbsp;</p>
 205
 206 <p class="whs5"># create a regular
 207  1D algorithm for the faces</p>
 208
 209 <p class="whs4">algo1D = quadra.Segment()</p>
 210
 211 <p class="whs4">&nbsp;</p>
 212
 213 <p class="whs5"># define &quot;NumberOfSegments&quot;
 214  hypothesis to cut</p>
 215
 216 <p class="whs5"># all the edges in
 217  a fixed number of segments</p>
 218
 219 <p class="whs4">algo1D.NumberOfSegments(4)</p>
 220
 221 <p class="whs4">&nbsp;</p>
 222
 223 <p class="whs5"># create a quadrangle
 224  2D algorithm for the faces</p>
 225
 226 <p class="whs4">quadra.Quadrangle()</p>
 227
 228 <p class="whs4">&nbsp;</p>
 229
 230 <p class="whs5"># construct a submesh
 231  on the edge with a local hypothesis</p>
 232
 233 <p class="whs4">algo_local = quadra.Segment(EdgeX)</p>
 234
 235 <p class="whs4">&nbsp;</p>
 236
 237 <p class="whs5"># define &quot;Arithmetic1D&quot;
 238  hypothesis to cut the edge<span style="margin-top: 0px;
 239                                                                                 margin-bottom: 0px;
 240                                                                                 font-family: 'Times New Roman', serif;">
 241  in several segments with increasing arithmetic length</span></p>
 242
 243 <p class="whs4">algo_local.Arithmetic1D(1, 4)</p>
 244
 245 <p class="whs4">&nbsp;</p>
 246
 247 <p class="whs5"># define &quot;Propagation&quot;
 248  hypothesis that propagates all other hypotheses</p>
 249
 250 <p class="whs5"># on all edges of the
 251  opposite side in case of quadrangular faces</p>
 252
 253 <p class="whs4">algo_local.Propagation()</p>
 254
 255 <p class="whs4">&nbsp;</p>
 256
 257 <p class="whs5"># compute the mesh</p>
 258
 259 <p class="whs4">quadra.Compute() </p>
 260
 261 <p class="whs4">&nbsp;</p>
 262
 263 <h3><a name=bookmark2>Editing of a mesh</a></h3>
 264
 265 <p class="whs4"><span style="font-family: 'Lucida Console', monospace;">import
 266  geompy</span></p>
 267
 268 <p class="whs4">import smesh</p>
 269
 270 <p class="whs4">&nbsp;</p>
 271
 272 <p class="whs4">def PrintMeshInfo(theMesh):</p>
 273
 274 <p class="whs4">&nbsp;&nbsp;&nbsp;&nbsp;aMesh
 275  = theMesh.GetMesh()</p>
 276
 277 <p class="whs4">&nbsp;&nbsp;&nbsp;&nbsp;print
 278  &quot;Information about mesh:&quot;</p>
 279
 280 <p class="whs4">&nbsp;&nbsp;&nbsp;&nbsp;print
 281  &quot;Number of nodes &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;:
 282  &quot;, aMesh.NbNodes()</p>
 283
 284 <p class="whs4">&nbsp;&nbsp;&nbsp;&nbsp;print
 285  &quot;Number of edges &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;:
 286  &quot;, aMesh.NbEdges()</p>
 287
 288 <p class="whs4">&nbsp;&nbsp;&nbsp;&nbsp;print
 289  &quot;Number of faces &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;:
 290  &quot;, aMesh.NbFaces()</p>
 291
 292 <p class="whs4">&nbsp;&nbsp;&nbsp;&nbsp;print
 293  &quot;Number of volumes &nbsp;&nbsp;&nbsp;&nbsp;:
 294  &quot;, aMesh.NbVolumes()</p>
 295
 296 <p class="whs4">&nbsp;&nbsp;&nbsp;&nbsp;pass</p>
 297
 298 <p class="whs4">&nbsp;</p>
 299
 300 <p class="whs5"># create a box</p>
 301
 302 <p class="whs4">box = geompy.MakeBox(0., 0., 0., 20.,
 303  20., 20.)</p>
 304
 305 <p class="whs4">geompy.addToStudy(box, &quot;box&quot;)</p>
 306
 307 <p class="whs4">&nbsp;</p>
 308
 309 <p class="whs5"># select one edge of
 310  the box for definition of a local hypothesis</p>
 311
 312 <p class="whs4">subShapeList = geompy.SubShapeAll(box,
 313  geompy.ShapeType[&quot;EDGE&quot;])</p>
 314
 315 <p class="whs4">edge = subShapeList[0]</p>
 316
 317 <p class="whs4">name = geompy.SubShapeName(edge, box)</p>
 318
 319 <p class="whs4">geompy.addToStudyInFather(box, edge, name)</p>
 320
 321 <p class="whs4">&nbsp;</p>
 322
 323 <p class="whs5"># create a mesh</p>
 324
 325 <p class="whs4">tria = smesh.Mesh(box, &quot;Mesh 2D&quot;)</p>
 326
 327 <p class="whs4">algo1D = tria.Segment()</p>
 328
 329 <p class="whs4">hyp1 = algo1D.NumberOfSegments(3)</p>
 330
 331 <p class="whs4">algo2D = tria.Triangle()</p>
 332
 333 <p class="whs4">hyp2 = algo2D.MaxElementArea(10.)</p>
 334
 335 <p class="whs4">&nbsp;</p>
 336
 337 <p class="whs5"># create a sub-mesh</p>
 338
 339 <p class="whs4">algo_local = tria.Segment(edge)</p>
 340
 341 <p class="whs4">hyp3 = algo_local.Arithmetic1D(1, 6)</p>
 342
 343 <p class="whs4">hyp4 = algo_local.Propagation()</p>
 344
 345 <p class="whs4">&nbsp;</p>
 346
 347 <p class="whs5"># compute the mesh</p>
 348
 349 <p class="whs4">tria.Compute()</p>
 350
 351 <p class="whs4">PrintMeshInfo(tria)</p>
 352
 353 <p class="whs4">&nbsp;</p>
 354
 355 <p class="whs5"># remove a local hypothesis</p>
 356
 357 <p class="whs4">mesh = tria.GetMesh()</p>
 358
 359 <p class="whs4">mesh.RemoveHypothesis(edge, hyp4)</p>
 360
 361 <p class="whs4">&nbsp;</p>
 362
 363 <p class="whs5"># compute the mesh</p>
 364
 365 <p class="whs4">tria.Compute()</p>
 366
 367 <p class="whs4">PrintMeshInfo(tria)</p>
 368
 369 <p class="whs4">&nbsp;</p>
 370
 371 <p class="whs5"># change the value
 372  of the 2D hypothesis</p>
 373
 374 <p class="whs4">hyp2.SetMaxElementArea(2.)</p>
 375
 376 <p class="whs4">&nbsp;</p>
 377
 378 <p class="whs5"># compute the mesh</p>
 379
 380 <p class="whs4">tria.Compute()</p>
 381
 382 <p class="whs4">PrintMeshInfo(tria) </p>
 383
 384 <p class="whs6">&nbsp;</p>
 385
 386 <h3><a name=bookmark3>Export of a Mesh</a></h3>
 387
 388 <p class="whs7">import geompy</p>
 389
 390 <p class="whs7">import smesh</p>
 391
 392 <p class="whs6">&nbsp;</p>
 393
 394 <p class="whs6"># create a box</p>
 395
 396 <p class="whs7">box = geompy.MakeBox(0.,
 397  0., 0., 100., 200., 300.)</p>
 398
 399 <p class="whs7">idbox = geompy.addToStudy(box,
 400  &quot;box&quot;)</p>
 401
 402 <p class="whs6">&nbsp;</p>
 403
 404 <p class="whs6"># create a mesh</p>
 405
 406 <p class="whs7">tetra = smesh.Mesh(box,
 407  &quot;MeshBox&quot;)</p>
 408
 409 <p class="whs6">&nbsp;</p>
 410
 411 <p class="whs7">algo1D = tetra.Segment()</p>
 412
 413 <p class="whs7">algo1D.NumberOfSegments(7)</p>
 414
 415 <p class="whs7">&nbsp;</p>
 416
 417 <p class="whs7">algo2D = tetra.Triangle()</p>
 418
 419 <p class="whs7">algo2D.MaxElementArea(800.)</p>
 420
 421 <p class="whs7">&nbsp;</p>
 422
 423 <p class="whs7">algo3D = tetra.Tetrahedron(smesh.NETGEN)</p>
 424
 425 <p class="whs7">algo3D.MaxElementVolume(900.)</p>
 426
 427 <p class="whs6">&nbsp;</p>
 428
 429 <p class="whs6"># compute the mesh</p>
 430
 431 <p class="whs7">tetra.Compute()</p>
 432
 433 <p class="whs6">&nbsp;</p>
 434
 435 <p class="whs6"># export the mesh in a
 436  MED file</p>
 437
 438 <p class="whs7">tetra.ExportMED(&quot;/tmp/meshMED.med&quot;,
 439  0) </p>
 440
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