/*!
\page netgen_2d_3d_hypo_page Netgen 2D and 3D hypotheses
Netgen 2D and Netgen 3D hypotheses work only with Netgen 1D-2D and
Netgen 1D-2D-3D algorithms. These algorithms do not require
definition of lower-level hypotheses and algorithms (2D and 1D for
meshing 3D objects and 1D for meshing 2D objects). They prove to be
useful if lower-level meshing is homogeneous for all wires and faces
of the meshed object.
\image html netgen2d.png
- Name - allows to define the name for the algorithm (Netgen
2D (or 3D) Parameters by default).
- Max Size - maximum linear dimensions for mesh cells.
- Second Order - if this box is checked in, the algorithm will
create second order nodes on the mesh, which actually will become
\ref adding_quadratic_elements_page "Quadratic".
- Fineness - ranging from Very Coarse to Very Fine allows to set the
level of meshing detalization using the three parameters below. You
can select Custom to define them manually.
- Growth rate - allows to define how much the linear dimensions of
two adjacent cells can differ (i.e. 0.3 means 30%).
- Nb. Segs per Edge and Nb Segs per Radius - allows to define the
minimum number of mesh segments in which edges and radiuses will be
split.
- Allow Quadrangles - allows to use quadrangle elements in a
triangle 2D mesh. This checkbox is not present in Netgen 3D parameters
because currently building a tetrahedral mesh with quadrangle faces is
not possible.
- Optimize - if this box is checked in, the algorithm will try to
create regular (possessing even sides) elements.
\image html netgen3d_simple.png
Netgen 2D simple parameters and Netgen 3D simple
parameters allow defining the size of elements for each
dimension.
\b 1D group allows defining the size of 1D elements in either of two ways:
- Number of Segments has the same sense as \ref
number_of_segments_anchor "Number of segments" hypothesis with
equidistant distribution.
- Average Length has the same sense as \ref
average_length_anchor "Average Length" hypothesis.
\b 2D group allows defining the size of 2D elements
- Length from edges if checked in, acts like \ref
length_from_edges_anchor "Length from Edges" hypothesis, else
- Max. Element Area defines the maximum element area like \ref
max_element_area_anchor "Max Element Area" hypothesis.
\b 3D groups allows defining the size of 3D elements.
- Length from faces if checked in, the area of sides of
volumic elements will be equal to an average area of 2D elements, else
- Max. Element Volume defines the maximum element volume like
\ref max_element_volume_hypo_page "Max Element Volume"
hypothesis.
\note Netgen algorithm does not strictly follow the input
parameters. The actual mesh can be more or less dense than
required. There are several factors in it:
- NETGEN does not actually use "NbOfSegments" parameter for discretization of
edge. This parameter is used only to define the local element size
(size at the given point), so local sizes of adjacent edges influence
each other.
- NETGEN additionally restricts the element size according to edge curvature.
- The local size of edges influences the size of close triangles.
- The order of elements and their size in the 1D mesh generated by
NETGEN differ from those in the 1D mesh generated by Regular_1D
algorithm, resulting in different 2D and 3D meshes.
*/