X-Git-Url: http://git.salome-platform.org/gitweb/?p=modules%2Fsmesh.git;a=blobdiff_plain;f=doc%2Fsalome%2Fgui%2FSMESH%2Finput%2F2d_meshing_hypo.doc;h=e019c8b87ff3c96bc64f282dc329f8b3395aab1b;hp=6d89e53d57465e4e41653c0e15f696ea7a6a9ea7;hb=5d68554076bbca0e1e95fb0db215a6c2b84b6c54;hpb=0635c9fc80f67d1e5dc0e94ec85f487286a92070 diff --git a/doc/salome/gui/SMESH/input/2d_meshing_hypo.doc b/doc/salome/gui/SMESH/input/2d_meshing_hypo.doc index 6d89e53d5..e019c8b87 100644 --- a/doc/salome/gui/SMESH/input/2d_meshing_hypo.doc +++ b/doc/salome/gui/SMESH/input/2d_meshing_hypo.doc @@ -2,61 +2,138 @@ \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 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 creation/edition dialog" -
-\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 opposite sides. 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 "Base Vertex tab of Quadrangle parameters creation/edition dialog" + +\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 "Enforced nodes tab of Quadrangle parameters creation/edition dialog" + +Enforced nodes tab allows for defining points where the +algorithm should create nodes. There are two ways to define positions +of the enforced nodes. + +Algorithm of creation of the enforced nodes is following. + +\image html hypo_quad_params_enfnodes_algo.png "Steps of the algorithm of creation of the enforced nodes" +
    +
  1. Left image: Positions of nodes are computed without taking into + account the enforced vertex (yellow point).
    2. +
  2. Middle image: A 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.
    3. +
  3. Right image: The meshed face is thus 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 detected node are + moved to the virtual edges and the quadrilateral elements are + constructed. +
+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.
*/