/*! \page extrusion_along_path_page Extrusion along a path \n In principle, Extrusion along a path works in the same way as \b Extrusion, the main difference is that we define not a vector, but a path of extrusion which must be a 1D mesh or 1D sub-mesh. 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 the examples the sample mesh will be extruded along different paths and with different parameters. This 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: \image html mesh_for_extr_along_path.png

Extrusion along a straight edge

(not using base point or angles)
\image html straight_before.png
The image shows a 1D path mesh, built on a linear edge, and the initial 2D mesh.
\image html straight_after.png
The image shows the result of extrusion of two edges (#1 and #2) of the initial mesh along the path. \n Node #1 of path mesh has been selected as Start node.

Extrusion along a curvilinear edge

(with and without angles)
\image html curvi_simple_before.png
The image shows a 1D path mesh, built on curvilinear edge, and the initial 2D mesh.
\image html curvi_simple_after.png
The central image shows the result of extrusion of one edge (#2) of the initial mesh along the path. \n Node #1 of path mesh has been selected as Start node.
\image html curvi_angles_after.png
The same, but using angles {45, 45, 45, 0, -45, -45, -45}

Extrusion of a 2D face along a mesh built on a wire

In this example the path mesh has been built on a wire containing 3 edges. Node 1 is a start node. Linear angle variation by 180 degrees has also been applied. \image html extr_along_wire_before.png
Meshed wire
\image html extr_along_wire_after.png
The resulting extrusion

Extrusion of 2d elements along a closed path

\image html circle_simple_before.png
The image shows a path mesh built on a closed edge (circle).
\image html circle_simple_after.png
The central image shows the result of extrusion of both faces of the initial mesh. \n Note, that no sewing has been done, so, there are six coincident nodes and two coincident faces in the resulting mesh.
\image html circle_angles_after.png
The same, but using angles {45, -45, 45, -45, 45, -45, 45, -45}

To use Extrusion along a path:
  1. From the \b Modification menu choose the Extrusion along a path item or click "Extrusion along a path" button in the toolbar. \image html image101.png
    "Extrusion along a path" button
    The following dialog common for line and planar elements will appear: \image html extrusion1.png
  2. In this dialog:
  3. There are two optional parameters, which can be very useful:
  4. Click \b Apply or Apply and Close button to confirm the operation. 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.

See Also a sample TUI Script of an \ref tui_extrusion_along_path "Extrusion along a Path" operation. */