X-Git-Url: http://git.salome-platform.org/gitweb/?a=blobdiff_plain;f=doc%2Fsalome%2Fgui%2FSMESH%2Finput%2F2d_meshing_hypo.doc;h=0ccb902e0025d7266fde1d8fc95b8901a9ad9458;hb=75d61804dc733ab5c810e416dec646406af11422;hp=6d89e53d57465e4e41653c0e15f696ea7a6a9ea7;hpb=0635c9fc80f67d1e5dc0e94ec85f487286a92070;p=modules%2Fsmesh.git
diff --git a/doc/salome/gui/SMESH/input/2d_meshing_hypo.doc b/doc/salome/gui/SMESH/input/2d_meshing_hypo.doc
index 6d89e53d5..0ccb902e0 100644
--- a/doc/salome/gui/SMESH/input/2d_meshing_hypo.doc
+++ b/doc/salome/gui/SMESH/input/2d_meshing_hypo.doc
@@ -2,61 +2,146 @@
\page a2d_meshing_hypo_page 2D Meshing Hypotheses
-
-
-- \ref max_element_area_anchor "Max Element Area"
-- \ref length_from_edges_anchor "Length from Edges"
-- \ref quadrangle_preference_anchor "Quadrangle Preference"
-- \ref triangle_preference_anchor "Triangle Preference"
-
+- \ref max_element_area_anchor "Max Element Area"
+- \ref length_from_edges_anchor "Length from Edges"
+- \ref hypo_quad_params_anchor "Quadrangle parameters"
-
\anchor max_element_area_anchor
Max Element Area
-Max Element Area hypothesis is applied for meshing of 2D faces
+Max Element Area hypothesis is applied for meshing of faces
composing your geometrical object. Definition of this hypothesis
-consists of setting the maximum area of meshing elements (depending on
-the chosen meshing algorithm it can be triangles or quadrangles),
-which will compose the mesh of these 2D faces.
+consists of setting the maximum area of mesh elements,
+which will compose the mesh of these faces.
\image html a-maxelarea.png
+\n
+
\image html max_el_area.png "In this example, Max. element area is very small compared to the 1D hypothesis"
See Also a sample TUI Script of a
-\ref tui_max_element_area "Maximum Element Area" hypothesis
-operation.
+\ref tui_max_element_area "Maximum Element Area" hypothesis operation.
-
\anchor length_from_edges_anchor
Length from Edges
-Length from edges hypothesis builds 2D mesh segments having a
-length calculated as an average edge length for a given wire.
+Length from edges hypothesis builds 2D mesh elements having a
+maximum linear size calculated as an average segment length for a wire
+of a given face.
See Also a sample TUI Script of a
\ref tui_length_from_edges "Length from Edges" hypothesis operation.
-
-\anchor quadrangle_preference_anchor
-Quadrangle Preference
+\anchor hypo_quad_params_anchor
+Quadrangle parameters
-This algorithm can be used only together with Quadrangle (Mapping)
-algorithm. It allows to build quadrangular meshes even if the number
-of nodes at the opposite edges of a meshed face is not equal,
-otherwise this mesh will contain some triangular elements.
-
-This hypothesis has one restriction on its work: the total quantity of
-segments on all four sides of the face must be even (divisible by 2).
+\image html hypo_quad_params_dialog.png "Quadrangle parameters: Transition"
-
-\anchor triangle_preference_anchor
-Triangle Preference
+Quadrangle parameters is a hypothesis for Quadrangle (Mapping) algorithm.
+
+Transition tab is used to define the algorithm of transition
+between opposite sides of faces with a different number of
+segments on them. The following types of transition
+algorithms are available:
+
+- Standard is the default case, when both triangles and quadrangles
+ are possible in the transition area along the finer meshed sides.
+- Triangle preference forces building only triangles in the
+ transition area along the finer meshed sides.
+ \note This type corresponds to Triangle Preference additional hypothesis,
+ which is obsolete now.
+- Quadrangle preference forces building only quadrangles in the
+ transition area along the finer meshed sides. This hypothesis has a
+ restriction: the total quantity of segments on all
+ four sides of the face must be even (divisible by 2).
+ \note This type corresponds to Quadrangle Preference additional hypothesis,
+ which is obsolete now.
+- Quadrangle preference (reversed) works in the same way and
+ with the same restriction as Quadrangle preference, but
+ the transition area is located along the coarser meshed sides.
+- Reduced type forces building only quadrangles and the transition
+ between the sides is made gradually, layer by layer. This type has
+ a limitation on the number of segments: one pair of opposite sides must have
+ the same number of segments, the other pair must have an even difference
+ between the numbers of segments on the sides. In addition, the number
+ of rows between sides with different discretization
+ should be enough for the transition. Following the fastest transition
+ pattern, three segments become one (see the image below), hence
+ the least number of face rows needed to reduce from Nmax segments
+ to Nmin segments is log3( Nmax / Nmin ). The number of
+ face rows is equal to the number of segments on each of equally
+ discretized sides.
+
+\image html reduce_three_to_one.png "The fastest transition pattern: 3 to 1"
+
+Base vertex tab allows using Quadrangle (Mapping)
+algorithm for meshing of trilateral faces. In this case it is
+necessary to select the vertex, which will be used as the fourth edge
+(degenerated).
+
+\image html hypo_quad_params_dialog_vert.png "Quadrangle parameters: Base Vertex"
+
+\image html hypo_quad_params_1.png "A face built from 3 edges"
+
+\image html hypo_quad_params_res.png "The resulting mesh"
+
+This parameter can be also used to mesh a segment of a circular face.
+Please, consider that there is a limitation on the selection of the
+vertex for the faces built with the angle > 180 degrees (see the picture).
+
+\image html hypo_quad_params_2.png "3/4 of a circular face"
+
+In this case, selection of a wrong vertex for the Base vertex
+parameter will generate a wrong mesh. The picture below
+shows the good (left) and the bad (right) results of meshing.
+
+\image html hypo_quad_params_res_2.png "The resulting meshes"
+
+\image html hypo_quad_params_dialog_enf.png "Quadrangle parameters: Enforced nodes"
+
+Enforced nodes tab allows defining points, where the
+algorithm should create nodes. There are two ways to define positions
+of the enforced nodes.
+
+ - \b Vertices group allows to set up shapes whose vertices will
+ define positions of the enforced nodes. Only vertices successfully
+ projected to the meshed face and located close enough to the
+ meshed face will be used to create the enforced nodes.
+ - \b Points group allows to explicitly define coordinates of
+ points used to create the enforced nodes. Only points successfully
+ projected to the meshed face and located close enough to the
+ meshed face will be used to create the enforced nodes.
+
+
+Let us see how the algorithm works:
+
+
+
+ - Initially positions of nodes are computed without taking into
+ account the enforced vertex (yellow point).
+\image html hypo_quad_params_enfnodes_algo1.png "Initial mesh"
+
+ - Then the node closest to the enforced vertex is
+ detected. Extreme nodes of the row and column of the detected node
+ are used to create virtual edges (yellow lines) ending at the
+ enforced vertex.
+\image html hypo_quad_params_enfnodes_algo2.png "Creation of virtual edges"
+
+ - Consequently, the meshed face is divided by the virtual
+ edges into four quadrilateral sub-domains each of which is meshed
+ as usually: the nodes of the row and column of the detected node are
+ moved to the virtual edges and the quadrilateral elements are
+ constructed.
+
+\image html hypo_quad_params_enfnodes_algo3.png "Final mesh"
+
+
+If there are several enforced vertices, the algorithm is applied
+recursively to the formed sub-domains.
+
+See Also a sample TUI Script of a
+\ref tui_quadrangle_parameters "Quadrangle Parameters" hypothesis.
-This algorithm can be used only together with Quadrangle (Mapping)
-algorithm. It allows to build triangular mesh faces in the refinement
-area if the number of nodes at the opposite edges of a meshed face is not equal,
-otherwise refinement area will contain some quadrangular elements.
*/