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 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
<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
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>
- <li>If the <b>Extrusion Along Vector</b> radio button is selected
+
+ <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>
+
<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.)
+\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
- 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>
</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
