/*!

\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 defining the name of the hypothesis (BLSURF
Parameters_n by default).</li>

<li><b>Physical Mesh</b> - if set to "Custom", allows user input in te
in <b>User size</b>, <b>Max Physical Size</b> and <b>Min Physical
Size</b> fields.
</li>

<li><b>User size</b> - defines the size of the generated mesh elements. </li>

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

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

<li><b>Geometrical mesh</b> - if set to "Custom", allows user input in
 <b>Angle Mesh S</b>, <b>Angle Mesh C</b> and
<b>Gradation</b> fields. These fields control
computation of the element size, so called <i>geometrical size</i>, conform to
the surface geometry considering local curvatures. \n
If both the <b>User size</b> and the <i>geometrical size</i> are defined, the
 eventual element size correspond to the least of the two. </li>

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

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

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

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

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

<li><b>Allow Quadrangles</b> - if checked, allows the creation of quadrilateral elements.</li>

<li><b>Patch independent</b> - if checked, 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++" allow the BLSURF software to
  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 the choice of multiple advanced
options, which appear, if selected, in a table where it is possible to
input the value of the option and to edit it later.</li>

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

</ul>

\n
The following options are commonly usable. The notion of <i>diag</i>
used in the descriptions means
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> × 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> × 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 average of several
values:<ul>
<li>-1 - the minimum is computed.</li>
<li>0 or 2 - the arithmetic average computed.
<li>1 - the geometric average is computed.</li>
</ul>
Default is 0.</li>

<li>\b CheckAdjacentEdges, \b CheckCloseEdges and \b CheckWellDefined
(integers) - gives the 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 more than 0.0, BLSURF removes
curves whose lengths are less than \b eps_collapse. To obtain an
approximate value of the length of a curve, it is arbitrarily
split into 20 edges. Default is 0.0.</li>

<li>\b eps_ends (real) - is used to detect the 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</i> and <i>P2</i> are the
extremities of a curve. Default is <i>diag</i>/500.0.</li>

<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>The created mesh will contain inverted elements if it is based on a shape,
      consisting of more than one face (box, cone, torus...) and if
      the option "Allow Quadrangles (Test)" has been checked before
      computation.</li>

  <li>SIGFPE exception is raised at the attempt to compute the mesh
      based on a box when the option "Patch independent" is checked.</li>

  <li>BLSURF algorithm cannot be used as a local algorithm (on
      sub-meshes) or as a provider of a low-level
      mesh for some 3D algorithms, because the BLSURF mesher (and
      consequently plugin) does not provide the 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;</li>
      </ul>
      </li>
</ul>

*/