<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 the ribs of the resulting 3D mesh. Free edges of input 2D elements
+generate logically horizontal rib segments. Logically vertical rib
+segments are generated from the nodes belonging to a sole input 2D element
+(the 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
<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>
the \ref filtering_elements "Selection filters" page.</li>
</ul>
</li>
+
<li>If the <b>Extrusion to Distance</b> radio button is selected
- - specify the translation vector by which the elements will be extruded.
+ <ul>
+ <li> specify the translation vector by which the elements will
+ be extruded.</li>
+ </ul>
</li>
- <p><br></p>
-
-\image html extrusionalongaline2.png
<li>If the <b>Extrusion Along Vector</b> radio button is selected
+\image html extrusionalongaline2.png
<ul>
- <li>specify the coordinates of the \b Vector along which the elements
+ <li>specify the components of the \b Vector along which the elements
will be extruded, either directly or by selecting the mesh face (the
normal to the face will define the vector),</li>
<li>specify the \b Distance of extrusion along the vector (it can
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 the selected faces is extruded along the \a average
of the \a normal vectors to the faces sharing the node. (Nodes and
edges cannot be extruded in this mode.)
+\image html extrusionalongaline3.png
<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
</ul>
<li>Specify the <b>Number of steps</b>.</li>
+
+ <li>Optionally specify <b>Scale Factors</b>. Each scale factor in
+ the list is applied to nodes of a corresponding extrusion step
+ unless <b>Linear Variation of Scale Factors</b> is checked, is
+ which case the scale factors are spread over all extrusion steps.</li>
+ <ul>
+ <li><b>Scaling Center</b> can be defined either using spin boxes
+ or by picking a node in the Viewer or by picking a geometrical
+ vertex in the Object Browser.</li>
+ <li>\b Add button adds a scale factor to the list.
+ \image html add.png
+ <center><em>"Add" button</em></center>
+ </li>
+ <li>\b Remove button removes selected scale factors from the list.
+ \image html remove.png
+ <center><em>"Remove" button</em></center>
+ </li>
+ </ul>
+
<li>If you activate <b>Generate Groups</b> check-box, the <em>result elements</em>
created from <em>selected elements</em> contained in groups will be
included into new groups named by pattern "<old group
