elements can be automatically grouped. Extrusion can be used to create
a \ref extrusion_struct "structured mesh from scratch".
-\image html extrusion_box.png "If you extrude several quadrangles, you get exactly same mesh as if you meshed a geometrical box (except that the initial quadrangles can be incorrectly oriented): quadrangles and segments on boundary of generated mesh are created"
+\image html extrusion_box.png "If you extrude several quadrangles, you get exactly the same mesh as if you meshed a geometrical box (except for that the initial quadrangles can be incorrectly oriented): quadrangles and segments are created on the boundary of the generated mesh"
<p>Any node, segment or 2D element can be extruded. Each type of
elements is extruded into a corresponding type of result elements:
<tr><td>Hexagonal polygon </td><td> Hexagonal prism </td></tr>
</table>
+When 2D elements are extruded, in addition to 3D elements segments are
+created on ribs of the result 3D mesh. Free edges of input 2D elements
+generate logically horizontal rib segments. Logically vertical rib
+segments are generated from nodes belonging to a sole input 2D element
+(a figure below illustrates this rule).
+
+\image html extru_rib_segs.png "Two triangles extruded: no vertical rib segments generated from nodes #2 and #3 as they are shared by both triangles"
+
<em>To use extrusion:</em>
<ol>
<li>From the \b Modification menu choose the \b Extrusion item or click
<em>"Extrusion" button</em>
</center>
-The following dialog, looking different depending on selected options,
-will appear:
+The following dialog will appear:
\image html extrusionalongaline1.png
-\image html extrusionalongaline2.png
-
-\image html extrusionalongaline3.png
-
</li>
<li>In this dialog:
<ul>
+ <li>Use \a Selection button to specify what you are going to
+ select at a given moment, \b Nodes, \b Edges or \b Faces.
+ \image html image120.png
+ <center><em>"Selection" button</em></center>
+ </li>
<li>Specify \b Nodes, \b Edges and \b Faces, which will be extruded, by one
of following means:
<ul>
- <li><b>Select the whole mesh, sub-mesh or group</b> activating this
- checkbox.</li>
+ <li><b>Select the whole mesh, sub-mesh or group</b> activating the
+ corresponding check-box.</li>
<li>Choose mesh elements with the mouse in the 3D Viewer. It is
possible to select a whole area with a mouse frame.</li>
<li>Input the element IDs directly in <b>Node IDs</b>, <b>Edge
<li>If the <b>Extrusion to Distance</b> radio button is selected
- specify the translation vector by which the elements will be extruded.
</li>
- <li>If the <b>Extrusion Along Vector</b> radio button is selected
+ <p><br></p>
+
+\image html extrusionalongaline2.png
+
+ <li>If the <b>Extrusion Along Vector</b> radio button is selected
<ul>
<li>specify the coordinates of the \b Vector along which the elements
will be extruded, either directly or by selecting the mesh face (the
be negative).</li>
</ul>
</li>
+ <p><br></p>
+
+\image html extrusionalongaline3.png
+
<li>If the <b>Extrusion By Normal</b> radio button is selected,
- every node of selected faces is extruded along the \a average
+ every node of the selected faces is extruded along the \a average
of the \a normal vectors to the faces sharing the node. (Nodes and
- edges can't be extruded in this mode.)
+ edges cannot be extruded in this mode.)
<ul>
<li>Specify the \b Distance of extrusion (it can be negative),</li>
<li>Use <b>Along average normal</b> check-box to specify along
- what vector the distance is measured.
+ which vector the distance is measured.
<ul>
<li>If it is \a activated the distance is measured along the
average normal mentioned above. </li>
<li>If it is \a deactivated every node is extruded along the
- average normal till its intersection with the virtual plane got
+ average normal till its intersection with a virtual plane obtained
by translation of the face sharing the node along its own normal
by the \b Distance.</li>
</ul>
\image html extrusionbynormal_alongavgnorm.png "'Along average normal' activated (to the left) and deactivated (to the right)"
<p></li>
- <li>Using <b>Use only input elements</b> check-box specify what
- elements
to use to compute the average normal.<ul>
+ <li><b>Use only input elements</b> check-box specifies what
+ elements
will be used to compute the average normal.<ul>
<li> If it is \a activated only selected faces, among faces
sharing the node, are used to compute the average normal at
the node. </li>
