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1  \chapter{The module \pycad}  \chapter{The module \pycad}
2  \label{PYCAD CHAP}  \label{PYCAD CHAP}
3    
4  \declaremodule{extension}{pyvisi}  
5    
6    \section{Introduction}
7    
8    
9    \section{\pycad Classes}
10    \declaremodule{extension}{esys.pycad}
11  \modulesynopsis{Python geometry description and meshing interface}  \modulesynopsis{Python geometry description and meshing interface}
12    
13    \subsection{Primitives}
14    
15    \begin{classdesc}{Point}{}
16    
17    \end{classdesc}
18    
19    \begin{classdesc}{Manifold1D}{}
20    
21    \end{classdesc}
22    
23    \begin{classdesc}{Manifold2D}{}
24    
25    \end{classdesc}
26    
27    \begin{classdesc}{Manifold3D}{}
28    
29    \end{classdesc}
30    
31    %============================================================================================================
32    \subsection{Transformations}
33    
34    Transformations are used to move geometrical objects in the 3-dimensional space:
35    
36    \begin{datadesc}{DEG}
37    The unit of degree. For instance use \code{90*DEG} for $90$ degrees.
38    \end{datadesc}
39    
40    \begin{datadesc}{RAD}
41    The unit of radiant. For instance use \code{math.pi*RAD} for $180$ degrees.
42    \end{datadesc}
43    
44    \begin{classdesc}{Translation}{\optional{b=[0,0,0]}}
45    defines a translation $x \to x+b$. \var{b} can be any object that can be converted
46    into a \numarray object of shape $(3,)$.
47    \end{classdesc}
48                  
49    \begin{classdesc}{Rotatation}{\optional{axis=[1,1,1], \optional{ point = [0,0,0], \optional{angle=0*RAD} } } }
50    defines a rotation by \var{angle} around axis through point \var{point} and direction \var{axis}.
51    \var{axis} and \var{point} can be any object that can be converted
52    into a \numarray object of shape $(3,)$.
53    \var{axis} does not have to be normalized but must have positive length. The right hand rule~\cite{RIGHTHANDRULE}
54    applies.
55    \end{classdesc}
56    
57    
58    \begin{classdesc}{Dilation}{\optional{factor=1., \optional{center=[0,0,0]}}}
59    defines a dilation by the expansion/contraction \var{factor} with
60    \var{center} as the dilation center.
61    \var{center} can be any object that can be converted
62    into a \numarray object of shape $(3,)$.
63    \end{classdesc}
64    
65    \begin{classdesc}{Reflection}{\optional{normal=[1,1,1], \optional{offset=0}}}
66    defines a reflection on a plane defined in normal form $n^t x = d$
67    where $n$ is the surface normal \var{normal} and $d$ is the plane \var{offset}.
68    \var{normal} can be any object that can be converted
69    into a \numarray object of shape $(3,)$.
70    \var{normal} does not have to be normalized but must have positive length.
71    \end{classdesc}
72    
73    \subsection{Properties}
74    
75    Property sets are used to bundle a set of geometrical objects in a group. The group
76    is identified by a name. Typically a property set is used to mark
77    subregions with share the same material properties or to mark portions of the boundary.
78    For efficiency, the \Design class object assigns a integer to each of its property sets,
79    a so-called tag \index{tag}. The appropriate tag is attached to the elements at generation time.
80    The \TagMap generated by the \Design allows mapping the a name onto the corresponding tag.
81    In order to avoid ambiguity it is recommended to have unique names of property sets within a \Design.
82    
83    
84    \begin{classdesc}{PropertySet}{name,*items}
85    defines a group geometrical objects which can be accessed through a \var{name}
86    The objects in the tuple \var{items} mast all be \ManifoldOneD, \ManifoldTwoD or \ManifoldThreeD objects.
87    \end{classdesc}
88    
89    
90    \begin{methoddesc}[PropertySet]{getManifoldClass}{}
91    returns the manifold class \ManifoldOneD, \ManifoldTwoD or \ManifoldThreeD expected from the items
92    in the property set.
93    \end{methoddesc}
94    
95    \begin{methoddesc}[PropertySet]{getDim}{}
96    returns the spatial dimension of the items
97    in the property set.
98    \end{methoddesc}
99    
100    \begin{methoddesc}[PropertySet]{getName}{}
101    returns the name of the set
102    \end{methoddesc}
103    
104    \begin{methoddesc}[PropertySet]{setName}{name}
105    sets the name. This name should be unique within a \Design.
106    \end{methoddesc}
107    
108    \begin{methoddesc}[PropertySet]{addItem}{*items}
109    adds a tuple of items. They need to be objects of class \ManifoldOneD, \ManifoldTwoD or \ManifoldThreeD.
110    \end{methoddesc}
111    
112    \begin{methoddesc}[PropertySet]{getItems}{}
113    returns the list of items
114    \end{methoddesc}
115    
116    \begin{methoddesc}[PropertySet]{clearItems}{}
117    clears the list of items
118    \end{methoddesc}
119    
120    \begin{methoddesc}[PropertySet]{getTag}{}
121    returns the tag used for this property set
122    \end{methoddesc}
123    
124    \subsection{Accessing \PropertySet Names}
125    During mesh generation the \PropertySet objects are not identified by their name but an integer tag (mainly to provide
126    a quicker indexing mechanism). The \TagMap which is generated by a \Design class object at mesh generation time
127    provides an mechanism to map the property set names onto tags and vice versa.
128    The following example illustrates the mechanis: In this case, the \TagMap \var{tm}
129    maps the names \var{x}, \var{a} onto the tags \var{5} and \var{4} and the tag \var{4}, respectively:  
130    \begin{python}
131    tm=TagMap({5 : "x" })
132    tm.setMap(a=1,x=4)
133    print tm.getTags("a"), tm.getTags("x")
134    \end{python}
135    Th output is
136    \begin{python}
137       [ 1 ], [ 5, 4 ]
138    \end{python}
139    
140    \begin{python}
141    d=Design()
142    d.add(PropertySet(name="a"))
143    print d.getTagMap().getTags("a")
144    \end{python}
145    
146    \begin{python}
147    d=Design()
148    d.add(PropertySet(name="a"))
149    domain=esys.finley.
150    print d.getTagMap().getTags("a")
151    \end{python}
152    
153    \begin{classdesc}{TagMap}{\optional{map = \{\} }}
154    defines a mapping between names (str) and tags (int).
155    The dictionary \var{map} sets an initial mapping from tag to name.
156    \end{classdesc}
157    
158    \begin{methoddesc}[TagMap]{setMap}{**kwargs}
159    adds a map from names to tags using keyword arguments. For instance
160    \var{top=1234} assigns the tag \var{123} to name \var{top}. The tag has to be integer.
161    If a tag has been assigned to a name before the mapping will be overwritten.
162    Notice that a single name can be assigned to different tags.
163    \end{methoddesc}
164    
165    \begin{methoddesc}[TagMap]{getTags}{\optional{name=None}}
166    returns a list of the tags assigned to \var{name}. If \var{name} is not present
167    a list of tags is returned.
168    \end{methoddesc}
169    
170     \begin{methoddesc}[TagMap]{getName}{\optional{tag=None}}
171    returns a the name assigned to \var{name}. If \var{tag} is not present
172    a list of all names is returned.
173    \end{methoddesc}
174    
175    
176    \begin{methoddesc}[TagMap]{getMapping}{}
177    returns a dictionary where the tags define the keys and the values the corresponding names.
178    \end{methoddesc}
179    
180    \begin{methoddesc}[TagMap]{map}{\optional{default=0}, \optional{**kwargs}}
181    returns a dictionary where the keys are the tags and the values are the corresponding values assigned
182    to the tag via the keyword arguments \var{**kwargs}. The value of \var{default} is used for tags
183    which map onto name with unspecified values.
184    
185    The following example demonstrate the usage:
186    \begin{python}
187    tm=TagMap(x=5)
188    tm.setMap(a=1,x=4,z=10)
189    print tm.map(default = "unknown", x="john",  a="peter")
190    \end{python}  
191    The output is
192    \begin{python}
193    { 5 : "john", 4: "john", 1 : "peter", 10 : "unknown" }
194    \end{python}  
195    \end{methoddesc}
196    
197    \begin{methoddesc}[TagMap]{insert}{data,\optional{default=0, \optional{**kwargs}}}
198    inserts the values assigned to name via the keyword arguments \var{**kwargs}
199    into the \Data object \var{Data}. The value \var{default} is used for names with no given value.
200    \end{methoddesc}
201    
202    \begin{methoddesc}[TagMap]{writeXML}{\optional{iostream=None}}
203    writes an XML serialization into the \var{iostream} or if not present returns the XML representation
204    as a string.
205    \end{methoddesc}
206    
207    \begin{methoddesc}[TagMap]{fillFromXML}{iostream}
208    uses XML data \var{iostream} defining an iostream or string. This method is the
209    inverse method of \var{writeXML}.
210    
211    The following example demonstrates the usage:
212    \begin{python}
213    tm=TagMap(x=5)
214    tm.setMap(a=1,x=4,z=10)
215    tm.writeXML(open("tag_map.xml", "w"))
216    tm2=TagMap()
217    tm2.fillFromXML(open("tag_map.xml", "r"))
218    \end{python}  
219    \end{methoddesc}        
220    
221    
222    
223    \section{Interface to \gmshextern}
224    \declaremodule{extension}{esys.pycad.gmsh}
225    \modulesynopsis{Python geometry description and meshing interface}
226    
227    \begin{classdesc}{Design}{
228    \optional{dim=3, \optional{element_size=1., \optional{order=1, \optional{keep_files=False}}}}}
229    The \class{Design} describes the geometry defined by primitives to be meshed.
230    The \var{dim} specifies the spatial dimension. The argument \var{element_size} defines the global
231    element size which is multiplied by the local scale to set the element size at each \Point.
232    The argument \var{order} defines the element order to be used. If \var{keep_files} is set to
233    \True temporary files a kept otherwise they are removed when the instance of the class is deleted.
234    \end{classdesc}
235    
236    
237    \begin{methoddesc}[Design]{setDim}{\optional{dim=3}}
238    sets the spatial dimension which needs to be $1$, $2$ or $3$.
239    \end{methoddesc}
240    
241    \begin{methoddesc}[Design]{getDim}{}
242    returns the spatial dimension.
243    \end{methoddesc}
244    
245    \begin{methoddesc}[Design]{setElementOrder}{\optional{order=1}}
246    sets the element order which needs to be $1$ or $2$.
247    \end{methoddesc}
248    
249    \begin{methoddesc}[Design]{getElementOrder}{}
250    returns the element order.
251    \end{methoddesc}
252    
253    
254    \begin{methoddesc}[Design]{setElementSize}{\optional{element_size=1}}
255    set the global element size. The local element size at a point is defined as
256    the global element size multipied by the local scale. The element size must be positive.
257    \end{methoddesc}
258    
259    
260    \begin{methoddesc}[Design]{getElementSize}{}
261    returns the global element size.
262    \end{methoddesc}
263    
264    \begin{memberdesc}[Design]{DELAUNAY}
265    the \gmshextern Delauny triangulator.
266    \end{memberdesc}
267    
268    \begin{memberdesc}[Design]{TETGEN}
269    the TetGen~\cite{TETGEN} triangulator.
270    \end{memberdesc}
271    
272    \begin{memberdesc}[Design]{TETGEN}
273    the NETGEN~\cite{NETGEN} triangulator.
274    \end{memberdesc}
275    
276    \begin{methoddesc}[Design]{setKeepFilesOn}{}
277    work files are kept at the end of the generation.
278    \end{methoddesc}
279    
280    \begin{methoddesc}[Design]{setKeepFilesOff}{}
281    work files are deleted at the end of the generation.
282    \end{methoddesc}
283    
284    \begin{methoddesc}[Design]{keepFiles}{}
285    returns \True if work files are kept. Otherwise \False is returned.
286    \end{methoddesc}
287    
288    \begin{methoddesc}[Design]{setScriptFileName}{\optional{name=None}}
289    set the filename for the \gmshextern input script. if no name is given a name with extension "geo" is generated.
290    \end{methoddesc}
291    
292    \begin{methoddesc}[Design]{getScriptFileName}{}
293    returns the name of the file for the \gmshextern script.
294    \end{methoddesc}
295    
296    
297    \begin{methoddesc}[Design]{setMeshFileName}{\optional{name=None}}
298    sets the name for the \gmshextern  mesh file. if no name is given a name with extension "msh" is generated.
299    \end{methoddesc}
300    
301    \begin{methoddesc}[Design]{getMeshFileName}{}
302    returns the name of the file for the gmsh msh
303    \end{methoddesc}
304    
305    
306    \begin{methoddesc}[Design]{addItems}{*items}
307    adds the tuple of var{items}. An item can be any primitive or a \class{PropertySet}.
308    \warning{If a \PropertySet is added as an item added object that are not
309    part of a \PropertySet are not considered in the messing.  
310    }
311    
312    \end{methoddesc}
313    
314    \begin{methoddesc}[Design]{getItems}{}
315    returns a list of the items
316    \end{methoddesc}
317    
318    \begin{methoddesc}[Design]{clearItems}{}
319    resets the items in design
320    \end{methoddesc}
321    
322    \begin{methoddesc}[Design]{getMeshHandler}{}
323    returns a handle to the mesh. The call of this method generates the mesh from the geometry and
324    returns a mechnism to access the mesh data. In the current implementation this
325    is this method returns a file name for a \gmshextern file containing the mesh data but this may change in
326    later versions.
327    \end{methoddesc}
328    
329    \begin{methoddesc}[Design]{getScriptString}{}
330    returns the \gmshextern script to generate the mesh as string.
331    \end{methoddesc}
332    
333    \begin{methoddesc}[Design]{getCommandString}{}
334    returns the \gmshextern command used to generate the mesh as string..
335    \end{methoddesc}
336    
337    \begin{methoddesc}[Design]{setOptions}{\optional{algorithm=None, \optional{ optimize_quality=True,\optional{ smoothing=1}}}}
338    sets options for the mesh generator. \var{algorithm} sets the algorithm to be used.
339    The algorithm needs to be \var{Design.DELAUNAY}
340    \var{Design.TETGEN}
341    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.  
342    \end{methoddesc}
343    
344    \begin{methoddesc}[Design]{getTagMap}{}
345    returns a \class{TagMap} to map the name \class{PropertySet} in the class to tag numbers generated by \gmshextern.
346    \end{methoddesc}

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