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

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<h1><img src="image101.gif" width="27px" height="24px" border="0" class="img_whs1">Extrusion along a path</h1>
<p>In principle, <span style="font-weight: bold;"><B>Extrusion along a path</B></span>
works in the same way as <span style="font-weight: bold;"><B>Extrusion</B></span>,
the main difference is that we define not a vector, but a path of extrusion
which must be a meshed edge. To get an idea of how this algorithm works,
examine several examples, starting from the most simple case of extrusion
along a straight edge. In all examples the same mesh will be extruded
along different paths and with different parameters. This sample 2D mesh
has two quadrangle faces and seven edges. Look at the picture, where white
digits are the node numbers and green are the element numbers:</p>
<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>
<p>&nbsp;</p>
<ul type="disc" class="whs3">
<li class=kadov-p><p><span style="font-weight: bold;"><B>Extrusion along
a straight edge</B></span> (not using base point or angles)</p></li>
</ul>
<table x-use-null-cells cellspacing="0" width="100%" class="whs4">
<col class="whs5">
<col class="whs5">
<tr valign="top" class="whs6">
<td width="50%" class="whs7">
<p class="whs8"><img src="pics/straight_before.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td>
<td width="50%" class="whs10">
<p class="whs11"><img src="pics/straight_after.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td></tr>
</table>
<p class="whs12">&nbsp;&nbsp;&nbsp;</p>
<p class="whs12">The left image shows a 1D path mesh, built
on a linear edge, and the initial 2D mesh. The right image shows the result
of extrusion of two edges (#1 and #2) of the initial mesh along the path.
Node #1 of path mesh has been selected as <span style="font-weight: bold;"><B>Start
node</B></span>.</p>
<p class="whs12">&nbsp;</p>
<ul type="disc" class="whs3">
<li class=kadov-p><p><span style="font-weight: bold;"><B>Extrusion along
a curvilinear edge</B></span> (with and without angles)</p></li>
</ul>
<table x-use-null-cells cellspacing="0" width="100%" class="whs4">
<col class="whs13">
<col class="whs13">
<col class="whs13">
<tr valign="top" class="whs6">
<td width="33.333%" class="whs14">
<p><img src="pics/curvi_simple_before.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td>
<td width="33.333%" class="whs15">
<p><img src="pics/curvi_simple_after.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td>
<td width="33.333%" class="whs16">
<p><img src="pics/curvi_angles_after.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td></tr>
<tr valign="top" class="whs6">
<td width="33.333%" class="whs17">
<p>The left image shows a 1D path mesh, built on curvilinear edge, and
the initial &nbsp;2D
mesh.</td>
<td width="33.333%" class="whs18">
<p>The central image shows the result of extrusion of one edge (#2) of
the initial mesh along the path. &nbsp;Node
#1 of path mesh has been selected as <span style="font-weight: bold;"><B>Start
node</B></span>.</td>
<td width="33.333%" class="whs19">
<p>The same, but using angles {45, 45, 45, 0, -45, -45, -45}</td></tr>
</table>
<p class="whs11">&nbsp;</p>
<ul type="disc" class="whs3">
<li class=kadov-p><p class="whs11"><span style="font-weight: bold;"><B>Extrusion
along a sub-mesh.</B></span></p></li>
</ul>
<table x-use-null-cells cellspacing="0" width="100%" class="whs4">
<col class="whs5">
<col class="whs5">
<tr valign="top" class="whs6">
<td width="50%" class="whs7">
<p><img src="pics/edge_wire_before.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td>
<td width="50%" class="whs10">
<p><img src="pics/edge_wire_after.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td></tr>
</table>
<p class="whs12">&nbsp;</p>
<p class="whs12">In this example the path mesh has been built
on a wire (polyline with six edges). The first edge of the wire was used
as <span style="font-weight: bold;"><B>Shape (edge)</B></span>, node #1 as <span
style="font-weight: bold;"><B>Start node</B></span>. The angles have been defined
as {10, 10, 10}. The middle edge (#4) of the initial mesh has been extruded.</p>
<p class="whs12">&nbsp;</p>
<ul type="disc" class="whs3">
<li class=kadov-p><p class="whs20">Extrusion
of 2d elements along a sub-mesh.</p></li>
</ul>
<table x-use-null-cells cellspacing="0" width="100%" class="whs4">
<col class="whs5">
<col class="whs5">
<tr valign="top" class="whs6">
<td width="50%" class="whs7">
<p><img src="pics/edge_wire_3d_before.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td>
<td width="50%" class="whs10">
<p><img src="pics/edge_wire_3d_after.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td></tr>
</table>
<p class="whs12">&nbsp;</p>
<p class="whs12">This extrusion bases on the same path mesh
as in the previous example but the third edge of the wire was set as <span
style="font-weight: bold;"><B>Shape (edge)</B></span> and node #4 as <span style="font-weight: bold;"><B>Start
node</B></span>. Please note, that the extrusion has been done in direction
from node #4 to node #3, i.e. against the wire direction. In this example
both faces of the initial mesh have been extruded.</p>
<p class="whs12">&nbsp;</p>
<ul type="disc" class="whs3">
<li class=kadov-p><p class="whs21">Extrusion of 2d elements
along a closed path.</p></li>
</ul>
<table x-use-null-cells cellspacing="0" width="100%" class="whs4">
<col class="whs13">
<col class="whs13">
<col class="whs13">
<tr valign="top" class="whs6">
<td width="33.333%" class="whs14">
<p><img src="pics/circle_simple_before.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td>
<td width="33.333%" class="whs15">
<p><img src="pics/circle_simple_after.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td>
<td width="33.333%" class="whs16">
<p><img src="pics/circle_angles_after.png" x-maintain-ratio="TRUE" width="389px" height="334px" border="0" class="img_whs9"></td></tr>
<tr valign="top" class="whs6">
<td width="33.333%" class="whs17">
<p>The left image shows a path mesh built on a closed edge (circle).</td>
<td width="33.333%" class="whs18">
<p>The central image shows the result of extrusion of both faces of the
initial mesh. Note, that no sewing has been done, so, there are six coincident
nodes and two coincident faces in the resulting mesh.</td>
<td width="33.333%" class="whs19">
<p>The same, but using angles {45, -45, 45, -45, 45, -45, 45, -45}</td></tr>
</table>
<p class="whs12">&nbsp;</p>
<p>&nbsp;</p>
<p class=TODO>To use Extrusion along a path:</p>
<p class="whs12">1. From the <span style="font-weight: bold;"><B>Modification
</B></span>menu choose the <span style="font-weight: bold;"><B>Extrusion along
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
following dialog box will appear:</p>
<p class="whs12">&nbsp;</p>
<p class=TODO
style="margin-left: 80px;"><img src="pics/extrusion1.png" x-maintain-ratio="TRUE" width="441px" height="541px" border="0" class="img_whs22"></p>
<p class="whs12">&nbsp;</p>
<p class="whs12">2. In the dialog box you should &nbsp;</p>
<ul type="disc" class="whs3">
<li class=kadov-p><p class="whs23">select the type of
elements which will be extruded (1D or 2D),</p></li>
<li class=kadov-p><p class="whs23">specify the <span style="font-weight: bold;"><B>IDs
of the elements</B></span> which will be extruded by selecting them in the
3D viewer or <span style="font-weight: bold;"><B>Select the whole mesh, submesh
or group</B></span>,</p></li>
<li class=kadov-p><p class="whs23">define the <span style="font-weight: bold;"><B>Path</B></span>
along which the elements will be extruded, </p></li>
</ul>
<p class="whs24">Path definition consists of several elements
</p>
<ul type="disc" class="whs3">
<li class=kadov-p><p class="whs25">Mesh
- <span style="font-weight: normal;">containing a 1D sub-mesh on the edge,
along which proceeds the extrusion.</span></p></li>
<li class=kadov-p><p class="whs25">Shape
(edge) - <span style="font-weight: normal;">as the mesh can be complex,
the edge is used to define the sub-mesh for the path.</span></p></li>
<li class=kadov-p><p class="whs25">Start
node - <span style="font-weight: normal;">&nbsp;the
first or the last node on the edge. It is used to define the direction
of extrusion.</span></p></li>
</ul>
<p class="whs12">&nbsp;</p>
<p class="whs12">3. There are two optional parameters, which
can be very useful.</p>
<ul type="disc" class="whs3">
<li class=kadov-p><p class="whs23">If the path of extrusion
is curvilinear, at each iteration the extruded shape is rotated to keep
its initial angularity to the curve. By default, the <span style="font-weight: bold;"><B>Base
Point</B></span> around which the shape is rotated is the mass center of the
shape, however, you can specify any point as the <span style="font-weight: bold;"><B>Base
Point</B></span> and the shape will be rotated with respect to this point.</p></li>
<li class=kadov-p><p class="whs23">The shape can also
be rotated around the path to get the resulting mesh in a helical fashion.
You can set the values of angles at the right, add them to the list of
angles at the left by pressing the <img src="image105.gif" width="26px" height="25px" border="0" class="img_whs26"> button and remove them
from the list by pressing the <img src="image106.gif" width="29px" height="28px" border="0" class="img_whs27"> button. </p></li>
</ul>
<p class="whs12">4. Click the <span style="font-weight: bold;"><B>Apply
</B></span>or <span style="font-weight: bold;"><B>OK </B></span>button. Mesh edges
will be extruded into faces, faces into volumes. The external surface
of the resulting 3d mesh (if faces have been extruded) is covered with
faces, and corners with edges. If the path is closed, the resulting mesh
can contain duplicated nodes and faces, because no sewing is done.</p>
<p class="whs12">&nbsp;</p>
<p>&nbsp;<span style="font-weight: bold;"><B>See
Also</B></span> a sample TUI Script of an <a href="modifying_meshes.htm#bookmark10">Extrusion
along a Path</a> operation. &nbsp;</p>
<p>&nbsp;</p>
<p>&nbsp;</p>
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