3 \page extrusion_page Extrusion
5 \n Extrusion is used to build mesh elements of plus one
6 dimension than the input ones. Boundary elements around generated
7 mesh of plus one dimension are additionally created. All created
8 elements can be automatically grouped. Extrusion can be used to create
9 a \ref extrusion_struct "structured mesh from scratch".
11 \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"
13 <p>Any node, segment or 2D element can be extruded. Each type of
14 elements is extruded into a corresponding type of result elements:
16 <tr><td><b>Extruded element</b></td><td><b> Result element </b></td></tr>
17 <tr><td>Node </td><td> Segment </td></tr>
18 <tr><td>Segment </td><td> Quadrilateral </td></tr>
19 <tr><td>Triangle </td><td> Pentahedron </td></tr>
20 <tr><td>Quadrilateral </td><td> Hexahedron </td></tr>
21 <tr><td>Polygon </td><td> Polyhedron </td></tr>
22 <tr><td>Hexagonal polygon </td><td> Hexagonal prism </td></tr>
25 When 2D elements are extruded, in addition to 3D elements segments are
26 created on the ribs of the resulting 3D mesh. Free edges of input 2D elements
27 generate logically horizontal rib segments. Logically vertical rib
28 segments are generated from the nodes belonging to a sole input 2D element
29 (the figure below illustrates this rule).
31 \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"
33 <em>To use extrusion:</em>
35 <li>From the \b Modification menu choose the \b Extrusion item or click
36 <em>"Extrusion"</em> button in the toolbar.
39 \image html image91.png
40 <em>"Extrusion" button</em>
43 The following dialog will appear:
45 \image html extrusionalongaline1.png
51 <li>Use \a Selection button to specify what you are going to
52 select at a given moment, \b Nodes, \b Edges or \b Faces.
53 \image html image120.png
54 <center><em>"Selection" button</em></center>
56 <li>Specify \b Nodes, \b Edges and \b Faces, which will be extruded, by one
59 <li><b>Select the whole mesh, sub-mesh or group</b> activating the
60 corresponding check-box.</li>
61 <li>Choose mesh elements with the mouse in the 3D Viewer. It is
62 possible to select a whole area with a mouse frame.</li>
63 <li>Input the element IDs directly in <b>Node IDs</b>, <b>Edge
64 IDs</b> and <b>Face IDs</b> fields. The selected elements will
65 be highlighted in the viewer, if the mesh is shown there.</li>
66 <li>Apply Filters. <b>Set filter</b> button allows to apply a
67 filter to the selection of elements. See more about filters in
68 the \ref filtering_elements "Selection filters" page.</li>
72 <li>If the <b>Extrusion to Distance</b> radio button is selected
74 <li> specify the translation vector by which the elements will
79 <li>If the <b>Extrusion Along Vector</b> radio button is selected
80 \image html extrusionalongaline2.png
82 <li>specify the components of the \b Vector along which the elements
83 will be extruded, either directly or by selecting the mesh face (the
84 normal to the face will define the vector),</li>
85 <li>specify the \b Distance of extrusion along the vector (it can
90 <li>If the <b>Extrusion By Normal</b> radio button is selected,
91 every node of the selected faces is extruded along the \a average
92 of the \a normal vectors to the faces sharing the node. (Nodes and
93 edges cannot be extruded in this mode.)
94 \image html extrusionalongaline3.png
96 <li>Specify the \b Distance of extrusion (it can be negative),</li>
97 <li>Use <b>Along average normal</b> check-box to specify along
98 which vector the distance is measured.
100 <li>If it is \a activated the distance is measured along the
101 average normal mentioned above. </li>
102 <li>If it is \a deactivated every node is extruded along the
103 average normal till its intersection with a virtual plane obtained
104 by translation of the face sharing the node along its own normal
105 by the \b Distance.</li>
107 The picture below shows a cross-section of a 2D mesh extruded
108 with <b>Along average normal</b> activated (to the left) and
109 deactivated (to the right).
111 \image html extrusionbynormal_alongavgnorm.png "'Along average normal' activated (to the left) and deactivated (to the right)"
114 <li><b>Use only input elements</b> check-box specifies what
115 elements will be used to compute the average normal.<ul>
116 <li> If it is \a activated only selected faces, among faces
117 sharing the node, are used to compute the average normal at
119 <li>Else all faces sharing the node are used.</li></ul>
121 The picture below shows a cross-section of a 2D mesh the upper
122 plane of which is extruded with <b>Use only input elements</b>
123 activated (to the left) and deactivated (to the right).
125 \image html extrusionbynormal_useonly.png "'Use only input elements' activated (to the left) and deactivated (to the right)"
130 <li>Specify the <b>Number of steps</b>.</li>
131 <li>If you activate <b>Generate Groups</b> check-box, the <em>result elements</em>
132 created from <em>selected elements</em> contained in groups will be
133 included into new groups named by pattern "<old group
134 name>_extruded" and "<old group name>_top". For example if a
135 selected quadrangle is included in \a g_Faces group (see figures
136 below) then result hexahedra will be included in \a
137 g_Faces_extruded group and a quadrangle created at the "top" of
138 extruded mesh will be included in \a g_Faces_top group. <br>
139 \image html extrusion_groups.png
140 \image html extrusion_groups_res.png
141 <p> This check-box is active only if there are some groups in the mesh.
145 <li>Click \b Apply or <b> Apply and Close</b> button to confirm the operation.</li>
149 \anchor extrusion_struct
150 <h2>Example: creation of a structured mesh from scratch</h2>
152 \image html image75.jpg "A node is extruded into a line of segments"
154 \image html image76.jpg "The line of segments is extruded into a quadrangle mesh"
156 \image html image77.jpg "The quadrangle mesh is revolved into a hexahedral mesh"
159 <br><b>See Also</b> a sample TUI Script of an
160 \ref tui_extrusion "Extrusion" operation.