smesh/doc/salome/gui/SMESH/input/blsurf_hypo.doc

/*!

\page blsurf_hypo_page BLSURF Parameters hypothesis

\n BLSURF Parameters hypothesis works only with <b>BLSURF</b> 2d
algorithm. This algorithm is a commercial software.

\image html blsurf_parameters.png

<ul>
<li><b>Name</b> - allows to define the name of the hypothesis (BLSURF
Parameters by default).</li>

<li><b>Physical Mesh</b> - if is set to "Custom", allows to set size
of mesh elements to generate in <b>User size</b> field.
</li>

<li><b>User size</b> - size of mesh elements to generate. </li>

<li><b>Max Physical Size</b> - is an upper limit of mesh element size. </li>

<li><b>Min Physical Size</b> - is a lower limit of mesh element size. </li>

<li><b>Geometrical mesh</b> - if is set to "Custom", allows to set
mesh element deflection from curves and surfaces and element
size change rate in <b>Angle Mesh S</b>, <b>Angle Mesh C</b> and
<b>Gradation</b> fields correspondingly. These fields control
computation of element size, so called <i>geometrical size</i>, conform to
the surface geometry considering local curvatures. \n
The eventual element size at each point will be minimum of <b>User
size</b>, if given, and the <i>geometrical size</i>. </li>

<li><b>Angle Mesh S</b> - maximal allowed angle in degrees at a mesh
node between the mesh face and the tangent to the geometrical surface. </li>

<li><b>Angle Mesh C</b> - maximal allowed angle in degrees at a mesh
node between the mesh edge and the tangent to the geometrical curve. </li>

<li><b>Max Geometrical Size</b> - is an upper limit of <i>geometrical size</i>.</li>

<li><b>Min Geometrical Size</b> - is a lower limit of <i>geometrical size</i>.</li>

<li><b>Gradation</b> - maximal allowed ratio between the lengths of
two adjacent edges. </li>

<li><b>Allow Quadrangles</b> - to create quadrilateral elements.</li>

<li><b>Patch independent</b> - if this box is checked on, geometrical
edges are not respected and all geometrical faces are meshed as one
hyper-face.</li>

\image html blsurf_parameters_advanced.png

<li><b>Topology</b> - allows creation of a conform mesh on a shell of
not sewed faces. 
<ul>
  <li>"From CAD" means that mesh conformity is assured by conformity
  of a shape.</li>
  <li>"Pre-process" and "Pre-process++" let BLSURF software
  pre-process the geometrical model to eventually produce a conform
  mesh. </li>
</ul>

<li><b>Verbosity level</b> - Defines the percentage of "verbosity" of
BLSURF [0-100].</li>

<li><b>Add option</b> - provides a choice of multiple advanced
options, each of which, if selected, appear in a table where you can
enter a value of the option and edit it later.</li>

<li><b>Clear option</b> - removes option selected in the table.

</ul>

\n
Commonly usable options are following. The name <i>diag</i> stands there for
the diagonal of the bounding box of the geometrical object to mesh.

<ul>
<li><b>topo_eps1</b> (real) - is the tolerance level inside a CAD
patch. By default is equal to <i>diag</i> <20> 10-4. This tolerance is used to
identify nodes to merge within one geometrical face when \b Topology
option is to pre-process. Default is <i>diag</i>/10.0.</li>

<li><b>topo_eps2</b> (real) - is the tolerance level between two CAD
patches. By default is equal to <i>diag</i> <20> 10-4. This tolerance is used to
identify nodes to merge over different geometrical faces when
\b Topology option is to pre-process. Default is <i>diag</i>/10.0.</li>

<li>\b LSS (real) - is an abbreviation for "length of sub-segment". It is
a maximal allowed length of a mesh edge. Default is 0.5.</li>

<li>\b frontal (integer)
<ul>
<li> 1 - the mesh generator inserts points with an advancing front method.</li>
<li> 0 - it inserts them with an algebraic method (on internal edges). This method is
slightly faster but generates less regular meshes. </li>
</ul>
Default is 0.</li>

<li>\b hinterpol_flag (integer) - determines the computation of an
interpolated value <i>v</i> between two points <i>P1</i> and <i>P2</i> on a
curve. Let <i>h1</i> be the value at point <i>P1,</i> <i>h2</i> be the value at point
<i>P2,</i> and <i>t</i> be a parameter varying from 0 to 1 when moving from <i>P1
to</i> <i>P2</i> . 
<ul>
<li>0 - the interpolation is linear: <i>v = h1 + t (h2 - h1 )</i></li>
<li>1 - the interpolation is geometric: <i>v = h1 * pow( h2/h1, t)</i></li>
<li>2 - the interpolation is sinusoidal: <i>v = (h1+h2)/2 +
(h1-h2)/2*cos(PI*t)</i></li>
</ul>
Default is 0.</li>

<li>\b hmean_flag (integer) - determines the computation of the mean of several
values:<ul>
<li>-1 - the minimum is computed.</li>
<li>0 or 2 - the arithmetic mean computed.
<li>1 - the geometric mean is computed.</li>
</ul>
Default is 0.</li>

<li>\b CheckAdjacentEdges, \b CheckCloseEdges and \b CheckWellDefined
(integers) - give number of calls of equally named subroutines the
purpose of which is to improve the mesh of domains having narrow
parts. At each iteration,\b CheckCloseEdges decreases the sizes of the
edges when two boundary curves are neighboring,\b CheckAdjacentEdges
balances the sizes of adjacent edges, and \b CheckWellDefined checks if
the parametric domain is well defined. Default values are 0.</li>


<li>\b CoefRectangle (real)- defines the relative thickness of the rectangles
used by subroutine \b CheckCloseEdges (see above). Default is 0.25.</li>

<li>\b eps_collapse (real) - if is more than 0.0, BLSURF removes
curves whose lengths are less than \b eps_collapse. Here, to obtain an
approximate value of the length of a curve, the latter is arbitrarily
split into 20 edges. Default is 0.0.</li>

<li>\b eps_ends (real) - is used to detect curves whose lengths are very
small, which sometimes constitutes an error. A message is printed
if<i> fabs(P2-P1) < eps_ends</i>, where </i>P1 and </i>P2 are the
extremities of a curve. Default is <i>diag</i>/500.0.

<li>\b prefix (char) - is a prefix of the files generated by
BLSURF. Default is "x".</li>

<li>\b refs (integer) - reference of a surface, used when exporting
files. Default is 1.</li>
</ul>

\n
The following advanced options are not documented and you can use them
at your own risk.
\n\n Interger variables:
<ul>
<li>    addsurf_ivertex</li>
<li>    background     </li>
<li>    coiter         </li>
<li>    communication  </li>
<li>    decim          </li>
<li>    export_flag    </li>
<li>    file_h         </li>
<li>    gridnu         </li>
<li>    gridnv         </li>
<li>    intermedfile   </li>
<li>    memory         </li>
<li>    normals        </li>
<li>    optim          </li>
<li>    pardom_flag    </li>
<li>    pinch          </li>
<li>    rigid          </li>
<li>    surforient     </li>
<li>    tconf          </li>
<li>    topo_collapse  </li>
</ul>
Real variables:
<ul>
<li>    addsurf_angle  </li>
<li>    addsurf_R      </li>
<li>    addsurf_H      </li>
<li>    addsurf_FG     </li>
<li>    addsurf_r      </li>
<li>    addsurf_PA     </li>
<li>    angle_compcurv </li>
<li>    angle_ridge    </li>
<li>    eps_pardom     </li>
</ul>
String variables:
<ul>
<li>    export_format  </li>
<li>    export_option  </li>
<li>    import_option  </li>  
</ul>


\n
Currently BLSURF plugin has the following limitations.
<ul>
<li>Mesh contains inverted elements, if it is based on shape, consisting of more than one face (box, cone, torus...) and if the option "Allow Quadrangles (Test)" was checked before computation.</li>

<li>SIGFPE exception is raised at trying to compute mesh, based on box, with checked option "Patch independent".</l>

<li>It has been found out that BLSURF algorithm can't be used as a local algorithm (on sub-meshes) and as a provider of low-level mesh for some 3D algorithms because BLSURF mesher (and consequently plugin) does not provide information on node parameters on edges (U) and faces (U,V). For example the following combinations of algorithms are impossible:
<ul>
<li> global MEFISTO or Quadrangle(mapping) + local BLSURF;</li>
<li> BLSUFR + Projection 2D from faces meshed by BLSURF;</li>
<li> local BLSURF + Extrusion 3D;
</ul>
</ul>

*/