3 \page blsurf_hypo_page BLSURF Parameters hypothesis
5 \n BLSURF Parameters hypothesis works only with <b>BLSURF</b> 2d
6 algorithm. This algorithm is a commercial software.
8 \image html blsurf_parameters.png
11 <li><b>Name</b> - allows defining the name of the hypothesis (BLSURF
12 Parameters_n by default).</li>
14 <li><b>Physical Mesh</b> - can be set to None, Custom or Size Map
16 <li>if set to "Custom", allows user input in the
17 in <b>User size</b>, <b>Max Physical Size</b> and <b>Min Physical
19 <li>if set to "Size Map", behaves like "Custom" mode and takes into account the custom elements sizes given in the Size Map tab.</li>
23 <li><b>User size</b> - defines the size of the generated mesh elements. </li>
25 <li><b>Max Physical Size</b> - defines the upper limit of mesh element size. </li>
27 <li><b>Min Physical Size</b> - defines the lower limit of mesh element size. </li>
29 <li><b>Geometrical mesh</b> - if set to "Custom", allows user input in
30 <b>Angle Mesh S</b>, <b>Angle Mesh C</b> and
31 <b>Gradation</b> fields. These fields control
32 computation of the element size, so called <i>geometrical size</i>, conform to
33 the surface geometry considering local curvatures. \n
34 If both the <b>User size</b> and the <i>geometrical size</i> are defined, the
35 eventual element size correspond to the least of the two. </li>
37 <li><b>Angle Mesh S</b> - maximum angle between the mesh face and the
38 tangent to the geometrical surface at each mesh node, in degrees. </li>
40 <li><b>Angle Mesh C</b> - maximum angle between the mesh edge and the
41 tangent to the geometrical curve at each mesh node, in degrees. </li>
43 <li><b>Max Geometrical Size</b> - defines the upper limit of the <i>geometrical size</i>.</li>
45 <li><b>Min Geometrical Size</b> - defines the lower limit of the <i>geometrical size</i>.</li>
47 <li><b>Gradation</b> - maximum ratio between the lengths of
48 two adjacent edges. </li>
50 <li><b>Allow Quadrangles</b> - if checked, allows the creation of quadrilateral elements.</li>
52 <li><b>Patch independent</b> - if checked, geometrical
53 edges are not respected and all geometrical faces are meshed as one
56 \image html blsurf_parameters_advanced.png
58 <li><b>Topology</b> - allows creation of a conform mesh on a shell of
61 <li>"From CAD" means that mesh conformity is assured by conformity
63 <li>"Pre-process" and "Pre-process++" allow the BLSURF software to
64 pre-process the geometrical model to eventually produce a conform
68 <li><b>Verbosity level</b> - Defines the percentage of "verbosity" of
71 <li><b>Add option</b> - provides the choice of multiple advanced
72 options, which appear, if selected, in a table where it is possible to
73 input the value of the option and to edit it later.</li>
75 <li><b>Clear option</b> - removes the option selected in the table.
80 The following options are commonly usable. The notion of <i>diag</i>
81 used in the descriptions means
82 the diagonal of the bounding box of the geometrical object to mesh.
85 <li><b>topo_eps1</b> (real) - is the tolerance level inside a CAD
86 patch. By default is equal to <i>diag</i> × 10-4. This tolerance is used to
87 identify nodes to merge within one geometrical face when \b Topology
88 option is to pre-process. Default is <i>diag</i>/10.0.</li>
90 <li><b>topo_eps2</b> (real) - is the tolerance level between two CAD
91 patches. By default is equal to <i>diag</i> × 10-4. This tolerance is used to
92 identify nodes to merge over different geometrical faces when
93 \b Topology option is to pre-process. Default is <i>diag</i>/10.0.</li>
95 <li>\b LSS (real) - is an abbreviation for "length of sub-segment". It is
96 a maximal allowed length of a mesh edge. Default is 0.5.</li>
98 <li>\b frontal (integer)
100 <li> 1 - the mesh generator inserts points with an advancing front method.</li>
101 <li> 0 - it inserts them with an algebraic method (on internal edges). This method is
102 slightly faster but generates less regular meshes. </li>
106 \anchor blsurf_hinterpol_flag
107 <li>\b hinterpol_flag (integer) - determines the computation of an
108 interpolated value <i>v</i> between two points <i>P1</i> and <i>P2</i> on a
109 curve. Let <i>h1</i> be the value at point <i>P1,</i> <i>h2</i> be the value at point
110 <i>P2,</i> and <i>t</i> be a parameter varying from 0 to 1 when moving from <i>P1
113 <li>0 - the interpolation is linear: <i>v = h1 + t (h2 - h1 )</i></li>
114 <li>1 - the interpolation is geometric: <i>v = h1 * pow( h2/h1, t)</i></li>
115 <li>2 - the interpolation is sinusoidal: <i>v = (h1+h2)/2 +
116 (h1-h2)/2*cos(PI*t)</i></li>
120 \anchor blsurf_hmean_flag
121 <li>\b hmean_flag (integer) - determines the computation of the average of several
123 <li>-1 - the minimum is computed.</li>
124 <li>0 or 2 - the arithmetic average computed.
125 <li>1 - the geometric average is computed.</li>
129 <li>\b CheckAdjacentEdges, \b CheckCloseEdges and \b CheckWellDefined
130 (integers) - gives the number of calls of equally named subroutines the
131 purpose of which is to improve the mesh of domains having narrow
132 parts. At each iteration,\b CheckCloseEdges decreases the sizes of the
133 edges when two boundary curves are neighboring,\b CheckAdjacentEdges
134 balances the sizes of adjacent edges, and \b CheckWellDefined checks if
135 the parametric domain is well defined. Default values are 0.</li>
138 <li>\b CoefRectangle (real)- defines the relative thickness of the rectangles
139 used by subroutine \b CheckCloseEdges (see above). Default is 0.25.</li>
141 <li>\b eps_collapse (real) - if more than 0.0, BLSURF removes
142 curves whose lengths are less than \b eps_collapse. To obtain an
143 approximate value of the length of a curve, it is arbitrarily
144 split into 20 edges. Default is 0.0.</li>
146 <li>\b eps_ends (real) - is used to detect the curves whose lengths are very
147 small, which sometimes constitutes an error. A message is printed
148 if<i> fabs(P2-P1) < eps_ends</i>, where <i>P1</i> and <i>P2</i> are the
149 extremities of a curve. Default is <i>diag</i>/500.0.</li>
151 <li>\b prefix (char) - is a prefix of the files generated by
152 BLSURF. Default is "x".</li>
154 <li>\b refs (integer) - reference of a surface, used when exporting
155 files. Default is 1.</li>
159 The following advanced options are not documented and you can use them
161 \n\n Integer variables:
163 <li> addsurf_ivertex</li>
164 <li> background </li>
166 <li> communication </li>
168 <li> export_flag </li>
172 <li> intermedfile </li>
176 <li> pardom_flag </li>
179 <li> surforient </li>
181 <li> topo_collapse </li>
185 <li> addsurf_angle </li>
188 <li> addsurf_FG </li>
190 <li> addsurf_PA </li>
191 <li> angle_compcurv </li>
192 <li> angle_ridge </li>
193 <li> eps_pardom </li>
197 <li> export_format </li>
198 <li> export_option </li>
199 <li> import_option </li>
202 \image html blsurf_parameters_sizemap.png
204 It is possible to define user sizes on faces, edges or verteces.
206 <li>Those faces, edges and verteces must be sub-shapes (from explode command) of the meshed geometry object.</li>
207 <li>Groups are currently not handled.</li>
208 <li>Multi-selection is possible.</li>
209 <li>The sizes are constant values.</li>
212 <br><b>See Also</b> a sample TUI Script of the \ref tui_blsurf "creation of a BLSurf hypothesis", including size map.
214 \anchor blsurf_sizemap_computation
215 <h2>Computation of the physical size</h2>
216 Here is the detail on the calculation of the size (from BLSurf documentation).
218 The size is obtained by querying sizemap functions associated to the input CAD object for surfaces, curves and points.
219 Each function can either return a value h (which is then trimmed between the two bounds hphymin and hphymax), or "no answer" (by not assigning a value to h), thus providing great flexibility in the specification of the sizes. The computation depends whether point P is internal to a surface, internal to a curve, or at the end of several curves:
221 <li> If point P is internal to a surface, the CAD surface size function is queried. If no answer is returned, one interpolates with the values at the vertices of the discretized interface curves.</li>
222 <li> If point P is internal to a curve, the CAD curve size function is queried first. If no answer is returned, the surface size function is queried for every adjacent surface and the mean value of the returned values is computed. If no answer is returned, sizes h1 and h2 at both ends of the curve are considered (see next item) and the interpolated value is computed.</li>
223 <li> If point P is at the extremity of several curves, the CAD point size function is queried first. If no answer is returned, the curve size function is queried for every adjacent curve and the mean value of the returned values is computed. If no answer is returned, the surface size function is queried for every adjacent surface and the mean value of the returned values is computed. If there is still no answer returned, the default value hphydef is kept.</li>
225 In order to compute the mean of several values, the arithmetic mean is used by default, but this can be modified by the parameter \ref blsurf_hmean_flag "hmean flag". In the same way, in order to interpolate two values, a linear interpolation is used by default, but this can be modified by \ref blsurf_hinterpol_flag "hinterpol flag".
229 Currently BLSURF plugin has the following limitations.
231 <li>The created mesh will contain inverted elements if it is based on a shape,
232 consisting of more than one face (box, cone, torus...) and if
233 the option "Allow Quadrangles (Test)" has been checked before
236 <li>SIGFPE exception is raised at the attempt to compute the mesh
237 based on a box when the option "Patch independent" is checked.</li>
239 <li>BLSURF algorithm cannot be used as a local algorithm (on
240 sub-meshes) or as a provider of a low-level
241 mesh for some 3D algorithms, because the BLSURF mesher (and
242 consequently plugin) does not provide the information on node
243 parameters on edges (U) and faces (U,V). For example the
244 following combinations of algorithms are impossible:
246 <li> global MEFISTO or Quadrangle(mapping) + local BLSURF;</li>
247 <li> BLSUFR + Projection 2D from faces meshed by BLSURF;</li>
248 <li> local BLSURF + Extrusion 3D;</li>