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pycad passes on more infromation from gmsh now.
1
2 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
3 %
4 % Copyright (c) 2003-2009 by University of Queensland
5 % Earth Systems Science Computational Center (ESSCC)
6 % http://www.uq.edu.au/esscc
7 %
8 % Primary Business: Queensland, Australia
9 % Licensed under the Open Software License version 3.0
10 % http://www.opensource.org/licenses/osl-3.0.php
11 %
12 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
13
14
15
16 \chapter{The Module \pycad} \label{PYCAD CHAP}
17
18
19 \section{Introduction}
20
21 \pycad provides a simple way to build a mesh for your finite element
22 simulation. You begin by building what we call a \class{Design} using
23 primitive geometric objects, and then to go on to build a mesh from
24 this. The final step of generating the mesh from a \class{Design}
25 uses freely available mesh generation software, such as \gmshextern.
26
27 A \class{Design} is built by defining points, which are used to specify
28 the corners of geometric objects and the vertices of curves. Using
29 points you construct more interesting objects such as lines,
30 rectangles, and arcs. By adding many of these objects into what we
31 call a \class{Design}, you can build meshes for arbitrarily complex 2-D
32 and 3-D structures.
33
34 \section{The Unit Square}
35 So the simplest geometry is the unit square. First we generate the
36 corner points
37 \begin{python}
38 from esys.pycad import *
39 p0=Point(0.,0.,0.)
40 p1=Point(1.,0.,0.)
41 p2=Point(1.,1.,0.)
42 p3=Point(0.,1.,0.)
43 \end{python}
44 which are then linked to define the edges of the square
45 \begin{python}
46 l01=Line(p0,p1)
47 l12=Line(p1,p2)
48 l23=Line(p2,p3)
49 l30=Line(p3,p0)
50 \end{python}
51 The lines are put together to form a loop
52 \begin{python}
53 c=CurveLoop(l01,l12,l23,l30)
54 \end{python}
55 The orientation of the line defining the \class{CurveLoop} is important. It is assumed that the surrounded
56 area is to the left when moving along the lines from their starting points towards the end points. Moreover,
57 the line need to form a closed loop.
58
59 We use the \class{CurveLoop} to define a surface
60 \begin{python}
61 s=PlaneSurface(c)
62 \end{python}
63 Notice there is difference between the \class{CurveLoop} defining the boundary
64 of the surface and the actually surface \class{PlaneSurface}. This difference becomes clearer in the next example with a hole. The direction of the lines is important.
65 New we are ready to define the geometry which described by an instance of \class{Design} class:
66 \begin{python}
67 d=Design(dim=2,element_size=0.05)
68 \end{python}
69 Here we use the two dimensional domain with a local element size in the finite element mesh of $0.05$.
70 We then add the surface \code{s} to the geometry
71 \begin{python}
72 d.addItems(s)
73 \end{python}
74 This will automatically import all items used to construct \code{s} into the \class{Design} \code{d}.
75 Now we are ready to construct a \finley FEM mesh and then write it to the file \file{quad.fly}:
76 \begin{python}
77 from esys.finley import MakeDomain
78 dom=MakeDomain(d)
79 dom.write("quad.fly")
80 \end{python}
81 In some cases it is useful to access the script used to generate the geometry. You can specify a specific name
82 for the script file. In our case we use
83 \begin{python}
84 d.setScriptFileName("quad.geo")
85 \end{python}
86 It is also useful to check error messages generated during the mesh generation process. \gmshextern writes
87 messages to the \file{.gmsh-errors} in your home directory.
88
89 If we put everything together we get the script
90 \begin{python}
91 from esys.pycad import *
92 from esys.pycad.gmsh import Design
93 from esys.finley import MakeDomain
94 p0=Point(0.,0.,0.)
95 p1=Point(1.,0.,0.)
96 p2=Point(1.,1.,0.)
97 p3=Point(0.,1.,0.)
98 l01=Line(p0,p1)
99 l12=Line(p1,p2)
100 l23=Line(p2,p3)
101 l30=Line(p3,p0)
102 c=CurveLoop(l01,l12,l23,l30)
103 s=PlaneSurface(c)
104 d=Design(dim=2,element_size=0.05)
105 d.setScriptFileName("quad.geo")
106 d.addItems(s)
107 pl1=PropertySet("sides",l01,l23)
108 pl2=PropertySet("top_and_bottom",l12,l30)
109 d.addItems(pl1, pl2)
110 dom=MakeDomain(d)
111 dom.write("quad.fly")
112 \end{python}
113 This example is included with the software in
114 \file{quad.py} in the \ExampleDirectory.
115
116 There are three extra statements which we have not discussed yet: By default the mesh used to subdivide
117 the boundary are not written into the mesh file mainly to reduce the size of the data file. One need to explicitly add the lines to the \Design which should be present in the mesh data. Here we additionally labeled the
118 lines on the top and the bottom with the name ``top_and_bottom`` and the lines on the left and right hand side
119 with the name ``sides`` using \class{PropertySet} objects. The labeling is convenient
120 when using tagging \index{tagging}, see Chapter~\ref{ESCRIPT CHAP}.
121
122 \begin{figure}
123 \centerline{\includegraphics[width=\figwidth]{figures/quad.eps}}
124 \caption{Trapozid with triangle Hole.}
125 \label{fig:PYCAD 0}
126 \end{figure}
127
128 If you have \gmshextern installed you can run the example and view the geometry and mesh with:
129 \begin{python}
130 escript quad.py
131 gmsh quad.geo
132 gmsh quad.msh
133 \end{python}
134 You can access error messages from \gmshextern in the \file{.gmsh-errors} in your home directory.
135 See Figure~\ref{fig:PYCAD 0} for a result.
136
137 In most cases it is best practice to generate the mesh and to solve the mathematical
138 model in to different scripts. In our example you can read the \finley mesh into your simulation
139 code\footnote{\gmshextern files can be directly read using the \function{ReadGmsh}, see Chapter~\ref{CHAPTER ON FINLEY}} using
140 \begin{python}
141 from finley import ReadMesh
142 mesh=ReadMesh("quad.fly")
143 \end{python}
144 Note that the underlying mesh generation software will not accept all
145 the geometries you can create with \pycad. For example, \pycad
146 will happily allow you to create a 2-D \class{Design} that is a
147 closed loop with some additional points or lines lying outside of the
148 enclosed area, but \gmshextern will fail to create a mesh for it.
149
150 \begin{figure}
151 \centerline{\includegraphics[width=\figwidth]{figures/trap.eps}}
152 \caption{Trapozid with triangle Hole.}
153 \label{fig:PYCAD 1}
154 \end{figure}
155
156
157 \section{Holes}
158 The example included below shows how to use \pycad to create a 2-D mesh
159 in the shape of a trapezoid with a cut-out area, see Figure~\ref{fig:PYCAD 1}:
160 \begin{python}
161 from esys.pycad import *
162 from esys.pycad.gmsh import Design
163 from esys.finley import MakeDomain
164
165 # A trapezoid
166 p0=Point(0.0, 0.0, 0.0)
167 p1=Point(1.0, 0.0, 0.0)
168 p2=Point(1.0, 0.5, 0.0)
169 p3=Point(0.0, 1.0, 0.0)
170 l01=Line(p0, p1)
171 l12=Line(p1, p2)
172 l23=Line(p2, p3)
173 l30=Line(p3, p0)
174 c=CurveLoop(l01, l12, l23, l30)
175
176 # A small triangular cutout
177 x0=Point(0.1, 0.1, 0.0)
178 x1=Point(0.5, 0.1, 0.0)
179 x2=Point(0.5, 0.2, 0.0)
180 x01=Line(x0, x1)
181 x12=Line(x1, x2)
182 x20=Line(x2, x0)
183 cutout=CurveLoop(x01, x12, x20)
184
185 # Create the surface with cutout
186 s=PlaneSurface(c, holes=[cutout])
187
188 # Create a Design which can make the mesh
189 d=Design(dim=2, element_size=0.05)
190
191 # Add the trapezoid with cutout
192 d.addItems(s)
193
194 # Create the geometry, mesh and Escript domain
195 d.setScriptFileName("trapezoid.geo")
196 d.setMeshFileName("trapezoid.msh")
197 domain=MakeDomain(d)
198 # write mesh to a finley file:
199 domain.write("trapezoid.fly")
200 \end{python}
201 This example is included with the software in
202 \file{trapezoid.py} in the \ExampleDirectory.
203
204 A \code{CurveLoop} is used to connect several lines into a single curve.
205 It is used in the example above to create the trapezoidal outline for the grid
206 and also for the triangular cutout area.
207 You can use any number of lines when creating a \class{CurveLoop}, but
208 the end of one line must be identical to the start of the next.
209
210
211 \begin{figure}
212 \centerline{\includegraphics[width=\figwidth]{figures/brick.eps}}
213 \caption{Three dimensional Block.}
214 \label{fig:PYCAD 2}
215 \end{figure}
216
217 \section{A 3D example}
218 In this section we discuss the definition of 3D geometries. The example is the unit cube, see Figure~\ref{fig:PYCAD 2}. First we generate the vertices of the cube:
219 \begin{python}
220 from esys.pycad import *
221 p0=Point(0.,0.,0.)
222 p1=Point(1.,0.,0.)
223 p2=Point(0.,1.,0.)
224 p3=Point(1.,1.,0.)
225 p4=Point(0.,0.,1.)
226 p5=Point(1.,0.,1.)
227 p6=Point(0.,1.,1.)
228 p7=Point(1.,1.,1.)
229 \end{python}
230 We connect the points to form the bottom and top surfaces of the cube:
231 \begin{python}
232 l01=Line(p0,p1)
233 l13=Line(p1,p3)
234 l32=Line(p3,p2)
235 l20=Line(p2,p0)
236 bottom=PlaneSurface(CurveLoop(l01,l13,l32,l20))
237 \end{python}
238 and
239 \begin{python}
240 l45=Line(p4,p5)
241 l57=Line(p5,p7)
242 l76=Line(p7,p6)
243 l64=Line(p6,p4)
244 top=PlaneSurface(CurveLoop(l45,l57,l76,l64))
245 \end{python}
246 To form the front face we introduce the two additional lines connecting the left and right front
247 points of the the \code{top} and \code{bottom} face:
248 \begin{python}
249 l15=Line(p1,p5)
250 l40=Line(p4,p0)
251 \end{python}
252 To form the front face we encounter the problem as the line \code{l45} used to define the
253 \code{top} face is pointing the wrong direction. In \pycad you can reversing direction of an
254 object by changing its sign. So we write \code{-l45} to indicate that the direction is to be reversed. With this notation we can write
255 \begin{python}
256 front=PlaneSurface(CurveLoop(l01,l15,-l45,l40))
257 \end{python}
258 Keep in mind that if you use \code{Line(p4,p5)} instead \code{-l45} both objects are treated as different although the connecting the same points with a straight line in the same direction. The resulting geometry would include an opening along the \code{p4}--\code{p5} connection. This will lead to an inconsistent mesh and may result in a failure of the volumetric mesh generator. Similarly we can define the other sides of the cube:
259 \begin{python}
260 l37=Line(p3,p7)
261 l62=Line(p6,p2)
262 back=PlaneSurface(CurveLoop(l32,-l62,-l76,-l37))
263 left=PlaneSurface(CurveLoop(-l40,-l64,l62,l20))
264 right=PlaneSurface(CurveLoop(-l15,l13,l37,-l57))
265 \end{python}
266 We can now put the six surfaces together to form a \class{SurfaceLoop} defining the
267 boundary of the volume of the cube:
268 \begin{python}
269 sl=SurfaceLoop(top,-bottom,front,back,left,right)
270 v=Volume(sl)
271 \end{python}
272 Similar to the definition of a \code{CurvedLoop} the orientation of the surfaces \code{SurfaceLoop} is relevant. In fact the surface normal direction defined by the the right hand rule needs to point outwards as indicated by the surface normals in
273 Figure~\ref{fig:PYCAD 2}. As the \code{bottom} face is directed upwards it is inserted with the minus sign
274 into the \code{SurfaceLoop} in order to adjust the orientation of the surface.
275
276 As in the 2D case, the \class{Design} class is used to define the geometry:
277 \begin{python}
278 from esys.pycad.gmsh import Design
279 from esys.finley import MakeDomain
280
281 des=Design(dim=3, element_size = 0.1, keep_files=True)
282 des.setScriptFileName("brick.geo")
283 des.addItems(v, top, bottom, back, front, left , right)
284
285 dom=MakeDomain(des)
286 dom.write("brick.fly")
287 \end{python}
288 Note that the \finley mesh file \file{brick.fly} will contain the
289 triangles used to define the surfaces as they are added to the \class{Design}.
290 The example script of the cube is included with the software in
291 \file{brick.py} in the \ExampleDirectory.
292
293 \begin{figure}
294 \centerline{\includegraphics[width=\figwidth]{figures/refine1.eps}}
295 \caption{Local refinement at the origin by
296 \var{local_scale=0.01}
297 with \var{element_size=0.3} and number of elements on the top set to 10.}
298 \label{fig:PYCAD 5}
299 \end{figure}
300
301 \section{Element Sizes}
302 The element size used globally is defined by the
303 \code{element_size} argument of the \class{Design}. The mesh generator
304 will try to use this mesh size everywhere in the geometry. In some cases it can be
305 desirable to use locally a finer mesh. A local refinement can be defined at each
306 \class{Point}:
307 \begin{python}
308 p0=Point(0.,0.,0.,local_scale=0.01)
309 \end{python}
310 Here the mesh generator will create a mesh with an element size which is by the factor \code{0.01}
311 times smaller than the global mesh size \code{element_size=0.3}, see Figure~\ref{fig:PYCAD 5}. The point where a refinement is defined must be a point of curve used to define the geometry.
312
313 Alternatively, one can define a mesh size along a curve by defining the number of elements to be used to subdivide the curve. For instance, to use $20$ element on line \code{l23} on uses:
314 \begin{python}
315 l23=Line(p2, p3)
316 l23.setElementDistribution(20)
317 \end{python}
318 Setting the number of elements on a curve overwrites the global mesh size \code{element_size}. The result is shown in Figure~\ref{fig:PYCAD 5}.
319
320
321
322 \section{\pycad Classes}
323 \declaremodule{extension}{esys.pycad}
324 \modulesynopsis{Python geometry description and meshing interface}
325
326 \subsection{Primitives}
327
328 Some of the most commonly-used objects in \pycad are listed here. For a more complete
329 list see the full API documentation.
330
331 \begin{classdesc}{Point}{x=0.,y=0.,z=0.\optional{,local_scale=1.}}
332 Create a point with from coordinates with local characteristic length \var{local_scale}
333 \end{classdesc}
334
335 \begin{classdesc}{Line}{point1, point2}
336 Create a line with between starting and ending points.
337 \end{classdesc}
338 \begin{methoddesc}[Line]{setElementDistribution}{n\optional{,progression=1\optional{,createBump=\False}}}
339 Defines the number of elements on the line. If set it overwrites the local length setting which would be applied. The progression factor \var{progression} defines the change of element size between neighboured elements. If \var{createBump} is set
340 progression is applied towards the centre of the line.
341 \end{methoddesc}
342 \begin{methoddesc}[Line]{resetElementDistribution}{}
343 removes a previously set element distribution from the line.
344 \end{methoddesc}
345 \begin{methoddesc}[Line]{getElemenofDistribution}{}
346 Returns the element distribution as tuple of
347 number of elements, progression factor and bump flag. If
348 no element distribution is set None is returned.
349 \end{methoddesc}
350
351
352 \begin{classdesc}{Spline}{point0, point1, ...}
353 A spline curve defined by a list of points \var{point0}, \var{point1},....
354 \end{classdesc}
355 \begin{methoddesc}[Spline]{setElementDistribution}{n\optional{,progression=1\optional{,createBump=\False}}}
356 Defines the number of elements on the line. If set it overwrites the local length setting which would be applied. The progression factor \var{progression} defines the change of element size between neighboured elements. If \var{createBump} is set
357 progression is applied towards the centre of the line.
358 \end{methoddesc}
359 \begin{methoddesc}[Spline]{resetElementDistribution}{}
360 removes a previously set element distribution from the line.
361 \end{methoddesc}
362 \begin{methoddesc}[Spline]{getElemenofDistribution}{}
363 Returns the element distribution as tuple of
364 number of elements, progression factor and bump flag. If
365 no element distribution is set None is returned.
366 \end{methoddesc}
367
368 \begin{classdesc}{BSpline}{point0, point1, ...}
369 A B-spline curve defined by a list of points \var{point0}, \var{point1},....
370 \end{classdesc}
371 \begin{methoddesc}[BSpline]{setElementDistribution}{n\optional{,progression=1\optional{,createBump=\False}}}
372 Defines the number of elements on the line. If set it overwrites the local length setting which would be applied. The progression factor \var{progression} defines the change of element size between neighboured elements. If \var{createBump} is set
373 progression is applied towards the centre of the line.
374 \end{methoddesc}
375 \begin{methoddesc}[BSpline]{resetElementDistribution}{}
376 removes a previously set element distribution from the line.
377 \end{methoddesc}
378 \begin{methoddesc}[BSpline]{getElemenofDistribution}{}
379 Returns the element distribution as tuple of
380 number of elements, progression factor and bump flag. If
381 no element distribution is set None is returned.
382 \end{methoddesc}
383
384 \begin{classdesc}{BezierCurve}{point0, point1, ...}
385 A Brezier spline curve defined by a list of points \var{point0}, \var{point1},....
386 \end{classdesc}
387 \begin{methoddesc}[BezierCurve]{setElementDistribution}{n\optional{,progression=1\optional{,createBump=\False}}}
388 Defines the number of elements on the line. If set it overwrites the local length setting which would be applied. The progression factor \var{progression} defines the change of element size between neighboured elements. If \var{createBump} is set
389 progression is applied towards the centre of the line.
390 \end{methoddesc}
391 \begin{methoddesc}[BezierCurve]{resetElementDistribution}{}
392 removes a previously set element distribution from the line.
393 \end{methoddesc}
394 \begin{methoddesc}[BezierCurve]{getElemenofDistribution}{}
395 Returns the element distribution as tuple of
396 number of elements, progression factor and bump flag. If
397 no element distribution is set None is returned.
398 \end{methoddesc}
399
400 \begin{classdesc}{Arc}{centre_point, start_point, end_point}
401 Create an arc by specifying a centre for a circle and start and end points. An arc may subtend an angle of at most $\pi$ radians.
402 \end{classdesc}
403 \begin{methoddesc}[Arc]{setElementDistribution}{n\optional{,progression=1\optional{,createBump=\False}}}
404 Defines the number of elements on the line. If set it overwrites the local length setting which would be applied. The progression factor \var{progression} defines the change of element size between neighboured elements. If \var{createBump} is set
405 progression is applied towards the centre of the line.
406 \end{methoddesc}
407 \begin{methoddesc}[Arc]{resetElementDistribution}{}
408 removes a previously set element distribution from the line.
409 \end{methoddesc}
410 \begin{methoddesc}[Arc]{getElemenofDistribution}{}
411 Returns the element distribution as tuple of
412 number of elements, progression factor and bump flag. If
413 no element distribution is set None is returned.
414 \end{methoddesc}
415
416 \begin{classdesc}{CurveLoop}{list}
417 Create a closed curve from the \code{list}. of
418 \class{Line}, \class{Arc}, \class{Spline}, \class{BSpline},
419 \class{BrezierSpline}.
420 \end{classdesc}
421
422 \begin{classdesc}{PlaneSurface}{loop, \optional{holes=[list]}}
423 Create a plane surface from a \class{CurveLoop}, which may have one or more holes
424 described by \var{list} of \class{CurveLoop}.
425 \end{classdesc}
426 \begin{methoddesc}[PlaneSurface]{setRecombination}{max_deviation}
427 the mesh generator will try to recombine triangular elements
428 into quadrilateral elements. \var{max_deviation} (in radians) defines the
429 maximum deviation of any angle in the quadrilaterals from the right angle.
430 Set \var{max_deviation}=\var{None} to remove recombination.
431 \end{methoddesc}
432 \begin{methoddesc}[PlaneSurface]{setTransfiniteMeshing}{\optional{orientation="Left"}}
433 applies 2D transfinite meshing to the surface.
434 \var{orientation} defines the orientation of triangles. Allowed values
435 are \var{``Left''}, \var{``Right''} or \var{``Alternate''}. The
436 boundary of the surface must be defined by three or four lines where an
437 element distribution must be defined on all faces where opposite
438 faces uses the same element distribution. No holes must be present.
439 \end{methoddesc}
440
441
442
443 \begin{classdesc}{RuledSurface}{list}
444 Create a surface that can be interpolated using transfinite interpolation.
445 \var{list} gives a list of three or four lines defining the boundary of the
446 surface.
447 \end{classdesc}
448 \begin{methoddesc}[RuledSurface]{setRecombination}{max_deviation}
449 the mesh generator will try to recombine triangular elements
450 into quadrilateral elements. \var{max_deviation} (in radians) defines the
451 maximum deviation of any angle in the quadrilaterals from the right angle.
452 Set \var{max_deviation}=\var{None} to remove recombination.
453 \end{methoddesc}
454 \begin{methoddesc}[RuledSurface]{setTransfiniteMeshing}{\optional{orientation="Left"}}
455 applies 2D transfinite meshing to the surface.
456 \var{orientation} defines the orientation of triangles. Allowed values
457 are \var{``Left''}, \var{``Right''} or \var{``Alternate''}. The
458 boundary of the surface must be defined by three or four lines where an
459 element distribution must be defined on all faces where opposite
460 faces uses the same element distribution. No holes must be present.
461 \end{methoddesc}
462
463
464 \begin{classdesc}{SurfaceLoop}{list}
465 Create a loop of \class{PlaneSurface} or \class{RuledSurface}, which defines the shell of a volume.
466 \end{classdesc}
467
468 \begin{classdesc}{Volume}{loop, \optional{holes=[list]}}
469 Create a volume given a \class{SurfaceLoop}, which may have one or more holes
470 define by the list of \class{SurfaceLoop}.
471 \end{classdesc}
472
473 \begin{classdesc}{PropertySet}{list}
474 Create a PropertySet given a list of 1-D, 2-D or 3-D items. See the section on Properties below for more information.
475 \end{classdesc}
476
477 %============================================================================================================
478 \subsection{Transformations}
479
480 Sometimes it's convenient to create an object and then make copies at
481 different orientations and in different sizes. Transformations are
482 used to move geometrical objects in the 3-dimensional space and to
483 resize them.
484
485 \begin{classdesc}{Translation}{\optional{b=[0,0,0]}}
486 defines a translation $x \to x+b$. \var{b} can be any object that can be converted
487 into a \numpy object of shape $(3,)$.
488 \end{classdesc}
489
490 \begin{classdesc}{Rotatation}{\optional{axis=[1,1,1], \optional{ point = [0,0,0], \optional{angle=0*RAD} } } }
491 defines a rotation by \var{angle} around axis through point \var{point} and direction \var{axis}.
492 \var{axis} and \var{point} can be any object that can be converted
493 into a \numpy object of shape $(3,)$.
494 \var{axis} does not have to be normalised but must have positive length. The right hand rule~\cite{RIGHTHANDRULE}
495 applies.
496 \end{classdesc}
497
498
499 \begin{classdesc}{Dilation}{\optional{factor=1., \optional{centre=[0,0,0]}}}
500 defines a dilation by the expansion/contraction \var{factor} with
501 \var{centre} as the dilation centre.
502 \var{centre} can be any object that can be converted
503 into a \numpy object of shape $(3,)$.
504 \end{classdesc}
505
506 \begin{classdesc}{Reflection}{\optional{normal=[1,1,1], \optional{offset=0}}}
507 defines a reflection on a plane defined in normal form $n^t x = d$
508 where $n$ is the surface normal \var{normal} and $d$ is the plane \var{offset}.
509 \var{normal} can be any object that can be converted
510 into a \numpy object of shape $(3,)$.
511 \var{normal} does not have to be normalised but must have positive length.
512 \end{classdesc}
513
514 \begin{datadesc}{DEG}
515 A constant to convert from degrees to an internal angle representation in radians. For instance use \code{90*DEG} for $90$ degrees.
516 \end{datadesc}
517
518 \subsection{Properties}
519
520 If you are building a larger geometry you may find it convenient to
521 create it in smaller pieces and then assemble them into the whole.
522 Property sets make this easy, and they allow you to name the smaller
523 pieces for convenience.
524
525 Property sets are used to bundle a set of geometrical objects in a
526 group. The group is identified by a name. Typically a property set
527 is used to mark subregions with share the same material properties or
528 to mark portions of the boundary. For efficiency, the \Design class
529 object assigns a integer to each of its property sets, a so-called tag
530 \index{tag}. The appropriate tag is attached to the elements at
531 generation time.
532
533 See the file \code{pycad/examples/quad.py} for an example using a {\it PropertySet}.
534
535
536 \begin{classdesc}{PropertySet}{name,*items}
537 defines a group geometrical objects which can be accessed through a \var{name}
538 The objects in the tuple \var{items} mast all be \ManifoldOneD, \ManifoldTwoD or \ManifoldThreeD objects.
539 \end{classdesc}
540
541
542 \begin{methoddesc}[PropertySet]{getManifoldClass}{}
543 returns the manifold class \ManifoldOneD, \ManifoldTwoD or \ManifoldThreeD expected from the items
544 in the property set.
545 \end{methoddesc}
546
547 \begin{methoddesc}[PropertySet]{getDim}{}
548 returns the spatial dimension of the items
549 in the property set.
550 \end{methoddesc}
551
552 \begin{methoddesc}[PropertySet]{getName}{}
553 returns the name of the set
554 \end{methoddesc}
555
556 \begin{methoddesc}[PropertySet]{setName}{name}
557 sets the name. This name should be unique within a \Design.
558 \end{methoddesc}
559
560 \begin{methoddesc}[PropertySet]{addItem}{*items}
561 adds a tuple of items. They need to be objects of class \ManifoldOneD, \ManifoldTwoD or \ManifoldThreeD.
562 \end{methoddesc}
563
564 \begin{methoddesc}[PropertySet]{getItems}{}
565 returns the list of items
566 \end{methoddesc}
567
568 \begin{methoddesc}[PropertySet]{clearItems}{}
569 clears the list of items
570 \end{methoddesc}
571
572 \begin{methoddesc}[PropertySet]{getTag}{}
573 returns the tag used for this property set
574 \end{methoddesc}
575
576 \section{Interface to the mesh generation software}
577 \declaremodule{extension}{esys.pycad.gmsh}
578 \modulesynopsis{Python geometry description and meshing interface}
579
580 The class and methods described here provide an interface to the mesh
581 generation software, which is currently \gmshextern. This interface could be
582 adopted to triangle or another mesh generation package if this is
583 deemed to be desirable in the future.
584
585 \begin{classdesc}{Design}{
586 \optional{dim=3, \optional{element_size=1., \optional{order=1, \optional{keep_files=False}}}}}
587 The \class{Design} describes the geometry defined by primitives to be meshed.
588 The \var{dim} specifies the spatial dimension. The argument \var{element_size} defines the global
589 element size which is multiplied by the local scale to set the element size at each \Point.
590 The argument \var{order} defines the element order to be used. If \var{keep_files} is set to
591 \True temporary files a kept otherwise they are removed when the instance of the class is deleted.
592 \end{classdesc}
593
594
595 \begin{methoddesc}[Design]{setDim}{\optional{dim=3}}
596 sets the spatial dimension which needs to be $1$, $2$ or $3$.
597 \end{methoddesc}
598
599 \begin{methoddesc}[Design]{getDim}{}
600 returns the spatial dimension.
601 \end{methoddesc}
602
603 \begin{methoddesc}[Design]{setElementOrder}{\optional{order=1}}
604 sets the element order which needs to be $1$ or $2$.
605 \end{methoddesc}
606
607 \begin{methoddesc}[Design]{getElementOrder}{}
608 returns the element order.
609 \end{methoddesc}
610
611
612 \begin{methoddesc}[Design]{setElementSize}{\optional{element_size=1}}
613 set the global element size. The local element size at a point is defined as
614 the global element size multiplied by the local scale. The element size must be positive.
615 \end{methoddesc}
616
617
618 \begin{methoddesc}[Design]{getElementSize}{}
619 returns the global element size.
620 \end{methoddesc}
621
622 \begin{memberdesc}[Design]{DELAUNAY}
623 the gmsh Delauny triangulator.
624 \end{memberdesc}
625
626 \begin{memberdesc}[Design]{TETGEN}
627 the TetGen~\cite{TETGEN} triangulator.
628 \end{memberdesc}
629
630 \begin{memberdesc}[Design]{NETGEN}
631 the NETGEN~\cite{NETGEN} triangulator.
632 \end{memberdesc}
633
634 \begin{methoddesc}[Design]{setKeepFilesOn}{}
635 work files are kept at the end of the generation.
636 \end{methoddesc}
637
638 \begin{methoddesc}[Design]{setKeepFilesOff}{}
639 work files are deleted at the end of the generation.
640 \end{methoddesc}
641
642 \begin{methoddesc}[Design]{keepFiles}{}
643 returns \True if work files are kept. Otherwise \False is returned.
644 \end{methoddesc}
645
646 \begin{methoddesc}[Design]{setScriptFileName}{\optional{name=None}}
647 set the file name for the gmsh input script. if no name is given a name with extension "geo" is generated.
648 \end{methoddesc}
649
650 \begin{methoddesc}[Design]{getScriptFileName}{}
651 returns the name of the file for the gmsh script.
652 \end{methoddesc}
653
654
655 \begin{methoddesc}[Design]{setMeshFileName}{\optional{name=None}}
656 sets the name for the gmsh mesh file. if no name is given a name with extension "msh" is generated.
657 \end{methoddesc}
658
659 \begin{methoddesc}[Design]{getMeshFileName}{}
660 returns the name of the file for the gmsh msh
661 \end{methoddesc}
662
663
664 \begin{methoddesc}[Design]{addItems}{*items}
665 adds the tuple of var{items}. An item can be any primitive or a \class{PropertySet}.
666 \warning{If a \PropertySet is added as an item added object that are not
667 part of a \PropertySet are not considered in the messing.
668 }
669
670 \end{methoddesc}
671
672 \begin{methoddesc}[Design]{getItems}{}
673 returns a list of the items
674 \end{methoddesc}
675
676 \begin{methoddesc}[Design]{clearItems}{}
677 resets the items in design
678 \end{methoddesc}
679
680 \begin{methoddesc}[Design]{getMeshHandler}{}
681 returns a handle to the mesh. The call of this method generates the mesh from the geometry and
682 returns a mechanism to access the mesh data. In the current implementation this
683 method returns a file name for a gmsh file containing the mesh data.
684 \end{methoddesc}
685
686 \begin{methoddesc}[Design]{getScriptString}{}
687 returns the gmsh script to generate the mesh as a string.
688 \end{methoddesc}
689
690 \begin{methoddesc}[Design]{getCommandString}{}
691 returns the gmsh command used to generate the mesh as string.
692 \end{methoddesc}
693
694 \begin{methoddesc}[Design]{setOptions}{\optional{algorithm=None, \optional{ optimize_quality=True,\optional{ smoothing=1}}}}
695 sets options for the mesh generator. \var{algorithm} sets the algorithm to be used.
696 The algorithm needs to be \var{Design.DELAUNAY}
697 \var{Design.TETGEN}
698 or \var{Design.NETGEN}. By default \var{Design.DELAUNAY} is used. \var{optimize_quality}=\True invokes an optimization of the mesh quality. \var{smoothing} sets the number of smoothing steps to be applied to the mesh.
699 \end{methoddesc}
700
701 \begin{methoddesc}[Design]{getTagMap}{}
702 returns a \class{TagMap} to map the name \class{PropertySet} in the class to tag numbers generated by gmsh.
703 \end{methoddesc}

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