/*!
-\page prism_3d_algo_page 3D extrusion meshing algorithm
+\page prism_3d_algo_page Extrusion 3D meshing algorithm
-3D extrusion algorithm can be used for meshing prisms, i.e. 3D shapes
+Extrusion 3D algorithm can be used for meshing prisms, i.e. 3D shapes
defined by two opposing faces having the same number of vertices and
edges. These two faces should be connected by quadrangle "side" faces.
+\image html prism_mesh.png "Clipping view of a mesh of a prism with non-planar base and top faces"
+
The prism is allowed to have sides composed of several faces. (A prism
side is a row of faces (or one face) connecting the corresponding edges of
the top and base faces). However, a prism
The shown sub-mesh is used by the algorithm to mesh
all eight prisms in the stacks.
-To use <em>3D extrusion</em> algorithm you need to assign algorithms
+To use <em>Extrusion 3D</em> algorithm you need to assign algorithms
and hypotheses of lower dimensions as follows.
(A sample picture below shows algorithms and hypotheses used to
mesh a cylinder with prismatic volumes).
<li> 1D algorithm and hypothesis that will be applied for meshing
(logically) vertical edges of the prism (which connect the top and the
base faces of the prism). In the sample picture above these are
- "Regular_1D" algorithm and "Nb. Segments" hypothesis named "Vertical
+ "Regular_1D" algorithm and "Number of Segments" hypothesis named "Vertical
Nb. Segments".</li>
</ul>
\ref constructing_submeshes_page "Construction of sub-meshes" are:
<ul>
<li> 1D and 2D algorithms and hypotheses that will be applied for
- meshing the top and the base prism faces. These faces can be meshed
+ meshing the top and the base prism
+ \ref submesh_shape_section "faces". These faces can be meshed
with any type of 2D elements: quadrangles, triangles, polygons or
- their mix. It is enough to define a sub-mesh on either the top or the base
- face. In the sample picture above, "NETGEN_1D2D" algorithm meshes
- "bottom disk" face with triangles. (1D algorithm is not
- assigned as "NETGEN_1D2D" does not require divided edges to create a 2D mesh.)
+ their mix. It is enough to define a sub-mesh on either the top or
+ the base face. In the sample picture above, "NETGEN_1D2D"
+ algorithm meshes "bottom disk" face with triangles. (1D algorithm
+ is not assigned as "NETGEN_1D2D" does not require divided edges to
+ create a 2D mesh.)
</li>
- <li> Optionally you can define a 1D sub-mesh on some vertical edges
- of stacked prisms, which will override the global 1D hypothesis mentioned
- above. In the <b>Prism stacks</b> picture, the
- vertical division is not equidistant on the whole length because
- a "Number Of Segments" hypothesis with Scale Factor=3 is assigned to
- the highlighted edge.
+ <li> Optionally you can define a 1D sub-mesh on some vertical
+ \ref submesh_shape_section "edges" of stacked prisms, which will
+ override the global 1D hypothesis mentioned above. In the <b>Prism
+ stacks</b> picture, the vertical division is not equidistant on
+ the whole length because a "Number Of Segments" hypothesis with
+ Scale Factor=3 is assigned to the highlighted edge.
</li></ul>
-\image html image157.gif "Prism with 3D extrusion meshing. Vertical division is different on neighbor edges because several local 1D hypotheses are assigned."
+If <em>Extrusion 3D</em> algorithm is assigned to a sub-mesh in a mesh
+with multiple sub-meshes, the described above approach may not work as
+expected. For example the bottom face may be meshed by other algorithm
+before <em>Extrusion 3D</em> have a chance to project a mesh from the
+base face. This thing can happen with vertical edges as well. All
+these can lead to either a meshing failure or to an incorrect meshing.
+
+In such a case, it's necessary to explicitly define algorithms
+that <em>Extrusion 3D</em> implicitly applies in a simple case:
+- assign \ref projection_1D2D algorithm to the top face and
+- assign a 1D algorithm to a group of all vertical edges.
+
+\image html image157.gif "Prism with Extrusion 3D meshing. Vertical division is different on neighbor edges because several local 1D hypotheses are assigned."
\sa a sample TUI Script of
-\ref tui_prism_3d_algo "Use 3D extrusion meshing algorithm".
+\ref tui_prism_3d_algo "Use Extrusion 3D meshing algorithm".
*/
