doc/salome/gui/SMESH/extrusion_along_a_path.htm

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 116 </script>
 117 <h1><img src="image101.gif" width="27px" height="24px" border="0" class="img_whs1">Extrusion along a path</h1>
 118
 119 <p>In principle, <span style="font-weight: bold;"><B>Extrusion along a path</B></span>
 120  works in the same way as <span style="font-weight: bold;"><B>Extrusion</B></span>,
 121  the main difference is that we define not a vector, but a path of extrusion
 122  which must be a meshed edge. To get an idea of how this algorithm works,
 123  examine several examples, starting from the most simple case of extrusion
 124  along a straight edge. In all examples the same mesh will be extruded
 125  along different paths and with different parameters. This sample 2D mesh
 126  has two quadrangle faces and seven edges. Look at the picture, where white
 127  digits are the node numbers and green are the element numbers:</p>
 128
 129 <p><span style="margin-left: 40px;"><img src="pics/mesh_for_extr_along_path.png" x-maintain-ratio="TRUE" width="387px" height="334px" border="0" class="img_whs2"> .</span></p>
 130
 131 <p>&nbsp;</p>
 132
 133 <ul type="disc" class="whs3">
 134
 135         <li class=kadov-p><p><span style="font-weight: bold;"><B>Extrusion along
 136  a straight edge</B></span> (not using base point or angles)</p></li>
 137 </ul>
 138
 139 <table x-use-null-cells cellspacing="0" width="100%" class="whs4">
 140 <col class="whs5">
 141 <col class="whs5">
 142
 143 <tr valign="top" class="whs6">
 144 <td width="50%" class="whs7">
 145 <p class="whs8"><img src="pics/straight_before.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td>
 146 <td width="50%" class="whs10">
 147 <p class="whs11"><img src="pics/straight_after.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td></tr>
 148 </table>
 149
 150 <p class="whs12">&nbsp;&nbsp;&nbsp;</p>
 151
 152 <p class="whs12">The left image shows a 1D path mesh, built
 153  on a linear edge, and the initial 2D mesh. The right image shows the result
 154  of extrusion of two edges (#1 and #2) of the initial mesh along the path.
 155  Node #1 of path mesh has been selected as <span style="font-weight: bold;"><B>Start
 156  node</B></span>.</p>
 157
 158 <p class="whs12">&nbsp;</p>
 159
 160 <ul type="disc" class="whs3">
 161
 162         <li class=kadov-p><p><span style="font-weight: bold;"><B>Extrusion along
 163  a curvilinear edge</B></span> (with and without angles)</p></li>
 164 </ul>
 165
 166 <table x-use-null-cells cellspacing="0" width="100%" class="whs4">
 167 <col class="whs13">
 168 <col class="whs13">
 169 <col class="whs13">
 170
 171 <tr valign="top" class="whs6">
 172 <td width="33.333%" class="whs14">
 173 <p><img src="pics/curvi_simple_before.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td>
 174 <td width="33.333%" class="whs15">
 175 <p><img src="pics/curvi_simple_after.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td>
 176 <td width="33.333%" class="whs16">
 177 <p><img src="pics/curvi_angles_after.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td></tr>
 178
 179 <tr valign="top" class="whs6">
 180 <td width="33.333%" class="whs17">
 181 <p>The left image shows a 1D path mesh, built on curvilinear edge, and
 182  the initial &nbsp;2D
 183  mesh.</td>
 184 <td width="33.333%" class="whs18">
 185 <p>The central image shows the result of extrusion of one edge (#2) of
 186  the initial mesh along the path. &nbsp;Node
 187  #1 of path mesh has been selected as <span style="font-weight: bold;"><B>Start
 188  node</B></span>.</td>
 189 <td width="33.333%" class="whs19">
 190 <p>The same, but using angles {45, 45, 45, 0, -45, -45, -45}</td></tr>
 191 </table>
 192
 193 <p class="whs11">&nbsp;</p>
 194
 195 <ul type="disc" class="whs3">
 196
 197         <li class=kadov-p><p class="whs11"><span style="font-weight: bold;"><B>Extrusion
 198  along a sub-mesh.</B></span></p></li>
 199 </ul>
 200
 201 <table x-use-null-cells cellspacing="0" width="100%" class="whs4">
 202 <col class="whs5">
 203 <col class="whs5">
 204
 205 <tr valign="top" class="whs6">
 206 <td width="50%" class="whs7">
 207 <p><img src="pics/edge_wire_before.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td>
 208 <td width="50%" class="whs10">
 209 <p><img src="pics/edge_wire_after.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td></tr>
 210 </table>
 211
 212 <p class="whs12">&nbsp;</p>
 213
 214 <p class="whs12">In this example the path mesh has been built
 215  on a wire (polyline with six edges). The first edge of the wire was used
 216  as <span style="font-weight: bold;"><B>Shape (edge)</B></span>, node #1 as <span
 217  style="font-weight: bold;"><B>Start node</B></span>. The angles have been defined
 218  as {10, 10, 10}. The middle edge (#4) of the initial mesh has been extruded.</p>
 219
 220 <p class="whs12">&nbsp;</p>
 221
 222 <ul type="disc" class="whs3">
 223
 224         <li class=kadov-p><p class="whs20">Extrusion
 225  of 2d elements along a sub-mesh.</p></li>
 226 </ul>
 227
 228 <table x-use-null-cells cellspacing="0" width="100%" class="whs4">
 229 <col class="whs5">
 230 <col class="whs5">
 231
 232 <tr valign="top" class="whs6">
 233 <td width="50%" class="whs7">
 234 <p><img src="pics/edge_wire_3d_before.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td>
 235 <td width="50%" class="whs10">
 236 <p><img src="pics/edge_wire_3d_after.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td></tr>
 237 </table>
 238
 239 <p class="whs12">&nbsp;</p>
 240
 241 <p class="whs12">This extrusion bases on the same path mesh
 242  as in the previous example but the third edge of the wire was set as <span
 243  style="font-weight: bold;"><B>Shape (edge)</B></span> and node #4 as <span style="font-weight: bold;"><B>Start
 244  node</B></span>. Please note, that the extrusion has been done in direction
 245  from node #4 to node #3, i.e. against the wire direction. In this example
 246  both faces of the initial mesh have been extruded.</p>
 247
 248 <p class="whs12">&nbsp;</p>
 249
 250 <ul type="disc" class="whs3">
 251
 252         <li class=kadov-p><p class="whs21">Extrusion of 2d elements
 253  along a closed path.</p></li>
 254 </ul>
 255
 256 <table x-use-null-cells cellspacing="0" width="100%" class="whs4">
 257 <col class="whs13">
 258 <col class="whs13">
 259 <col class="whs13">
 260
 261 <tr valign="top" class="whs6">
 262 <td width="33.333%" class="whs14">
 263 <p><img src="pics/circle_simple_before.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td>
 264 <td width="33.333%" class="whs15">
 265 <p><img src="pics/circle_simple_after.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td>
 266 <td width="33.333%" class="whs16">
 267 <p><img src="pics/circle_angles_after.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td></tr>
 268
 269 <tr valign="top" class="whs6">
 270 <td width="33.333%" class="whs17">
 271 <p>The left image shows a path mesh built on a closed edge (circle).</td>
 272 <td width="33.333%" class="whs18">
 273 <p>The central image shows the result of extrusion of both faces of the
 274  initial mesh. Note, that no sewing has been done, so, there are six coincident
 275  nodes and two coincident faces in the resulting mesh.</td>
 276 <td width="33.333%" class="whs19">
 277 <p>The same, but using angles {45, -45, 45, -45, 45, -45, 45, -45}</td></tr>
 278 </table>
 279
 280 <p class="whs12">&nbsp;</p>
 281
 282 <p>&nbsp;</p>
 283
 284 <p class=TODO>To use Extrusion along a path:</p>
 285
 286 <p class="whs12">1. From the <span style="font-weight: bold;"><B>Modification
 287  </B></span>menu choose the <span style="font-weight: bold;"><B>Extrusion along
 288  a path </B></span>item or click <img src="image101.gif" width="27px" height="24px" border="0" class="img_whs1"> button in the toolbar. The
 289  following dialog box will appear:</p>
 290
 291 <p class="whs12">&nbsp;</p>
 292
 293 <p class=TODO
 294         style="margin-left: 80px;"><img src="pics/extrusion1.png" x-maintain-ratio="TRUE" width="441px" height="541px" border="0" class="img_whs22"></p>
 295
 296 <p class="whs12">&nbsp;</p>
 297
 298 <p class="whs12">2. In the dialog box you should &nbsp;</p>
 299
 300 <ul type="disc" class="whs3">
 301
 302         <li class=kadov-p><p class="whs23">select the type of
 303  elements which will be extruded (1D or 2D),</p></li>
 304
 305         <li class=kadov-p><p class="whs23">specify the <span style="font-weight: bold;"><B>IDs
 306  of the elements</B></span> which will be extruded by selecting them in the
 307  3D viewer or <span style="font-weight: bold;"><B>Select the whole mesh, submesh
 308  or group</B></span>,</p></li>
 309
 310         <li class=kadov-p><p class="whs23">define the <span style="font-weight: bold;"><B>Path</B></span>
 311  along which the elements will be extruded, </p></li>
 312 </ul>
 313
 314 <p class="whs24">Path definition consists of several elements
 315  </p>
 316
 317 <ul type="disc" class="whs3">
 318
 319         <li class=kadov-p><p class="whs25">Mesh
 320  - <span style="font-weight: normal;">containing a 1D sub-mesh on the edge,
 321  along which proceeds the extrusion.</span></p></li>
 322
 323         <li class=kadov-p><p class="whs25">Shape
 324  (edge) - <span style="font-weight: normal;">as the mesh can be complex,
 325  the edge is used to define the sub-mesh for the path.</span></p></li>
 326
 327         <li class=kadov-p><p class="whs25">Start
 328  node - <span style="font-weight: normal;">&nbsp;the
 329  first or the last node on the edge. It is used to define the direction
 330  of extrusion.</span></p></li>
 331 </ul>
 332
 333 <p class="whs12">&nbsp;</p>
 334
 335 <p class="whs12">3. There are two optional parameters, which
 336  can be very useful.</p>
 337
 338 <ul type="disc" class="whs3">
 339
 340         <li class=kadov-p><p class="whs23">If the path of extrusion
 341  is curvilinear, at each iteration the extruded shape is rotated to keep
 342  its initial angularity to the curve. By default, the <span style="font-weight: bold;"><B>Base
 343  Point</B></span> around which the shape is rotated is the mass center of the
 344  shape, however, you can specify any point as the <span style="font-weight: bold;"><B>Base
 345  Point</B></span> and the shape will be rotated with respect to this point.</p></li>
 346
 347         <li class=kadov-p><p class="whs23">The shape can also
 348  be rotated around the path to get the resulting mesh in a helical fashion.
 349  You can set the values of angles at the right, add them to the list of
 350  angles at the left by pressing the <img src="image105.gif" width="26px" height="25px" border="0" class="img_whs26"> button and remove them
 351  from the list by pressing the <img src="image106.gif" width="29px" height="28px" border="0" class="img_whs27"> button. </p></li>
 352 </ul>
 353
 354 <p class="whs12">4. Click the <span style="font-weight: bold;"><B>Apply
 355  </B></span>or <span style="font-weight: bold;"><B>OK </B></span>button. Mesh edges
 356  will be extruded into faces, faces into volumes. The external surface
 357  of the resulting 3d mesh (if faces have been extruded) is covered with
 358  faces, and corners with edges. If the path is closed, the resulting mesh
 359  can contain duplicated nodes and faces, because no sewing is done.</p>
 360
 361 <p class="whs12">&nbsp;</p>
 362
 363 <p>&nbsp;<span style="font-weight: bold;"><B>See
 364  Also</B></span> a sample TUI Script of an <a href="modifying_meshes.htm#bookmark10">Extrusion
 365  along a Path</a> operation. &nbsp;</p>
 366
 367 <p>&nbsp;</p>
 368
 369 <p>&nbsp;</p>
 370
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