GridIn< dim, spacedim > Class Template Reference
[Grid classesInput]

List of all members.

Classes

class  ExcDBMESHWrongDimension
class  ExcGmshUnsupportedGeometry
class  ExcInvalidDBMeshFormat
class  ExcInvalidDBMESHInput
class  ExcInvalidGMSHInput
class  ExcInvalidVertexIndex
class  ExcNoTriangulationSelected
class  ExcUnknownIdentifier

Public Types

enum  Format {
  Default, ucd, dbmesh, xda,
  msh, netcdf, tecplot
}

Public Member Functions

 GridIn ()
void attach_triangulation (Triangulation< dim, spacedim > &tria)
void read (std::istream &in, Format format=Default)
void read (const std::string &in, Format format=Default)
void read_ucd (std::istream &in)
void read_dbmesh (std::istream &in)
void read_xda (std::istream &in)
void read_msh (std::istream &in)
void read_netcdf (const std::string &filename)
void read_tecplot (std::istream &in)

Static Public Member Functions

static std::string default_suffix (const Format format)
static Format parse_format (const std::string &format_name)
static std::string get_format_names ()

Static Protected Member Functions

static void debug_output_grid (const std::vector< CellData< dim > > &cells, const std::vector< Point< spacedim > > &vertices, std::ostream &out)

Protected Attributes

SmartPointer< Triangulation
< dim, spacedim > > 
tria

Static Private Member Functions

static void skip_empty_lines (std::istream &in)
static void skip_comment_lines (std::istream &in, const char comment_start)
static void parse_tecplot_header (std::string &header, std::vector< unsigned int > &tecplot2deal, unsigned int &n_vars, unsigned int &n_vertices, unsigned int &n_cells, std::vector< unsigned int > &IJK, bool &structured, bool &blocked)

Private Attributes

Format default_format


Detailed Description

template<int dim, int spacedim = dim>
class GridIn< dim, spacedim >

This class implements an input mechanism for grid data. It allows to read a grid structure into a triangulation object. At present, UCD (unstructured cell data), DB Mesh, XDA, Gmsh, Tecplot, NetCDF and Cubit are supported as input format for grid data. Any numerical data after the block of topological information is ignored. Notice also that at the moment in the codimension 1 case only UCD and Gmsh format are accepted.

Since the coarse mesh fed into a Triangulation object cannot have hanging nodes, strange things will happen if the input file has them. This is due to the fact that most mesh description formats do not store neighborship information between cells, so the grid reading functions have to regenerate it. They do so by checking whether two cells have a common face. If there are hanging nodes in a triangulation, adjacent cells have no common face, so the grid reader concludes that the adjacent cells have no neighbors along these faces and must therefore be at the boundary. In effect, an internal crack of the domain is introduced this way. Since such cases are very hard to detect, the library does not make any attempt to abort on such situations, and you will get a triangulation that probably does not do what you want.

Note: if you experience unexpected problems with the use of this class, be sure to read the documentation right until the end, and also read the documentation of the GridReordering class.

To read grid data, the triangulation to be fed with has to be empty. When giving a file which does not contain the assumed information or which does not keep to the right format, the state of the triangulation will be undefined afterwards. Upon input, only lines in one dimension and line and quads in two dimensions are accepted. All other cell types (e.g. triangles in two dimensions, quads and hexes in 3d) are rejected. The vertex and cell numbering in the input file, which need not be consecutively, is lost upon transfer to the triangulation object, since this one needs consecutively numbered elements.

Material indicators are accepted to denote the material ID of cells and to denote boundary part indication for lines in 2D. Read the according sections in the documentation of the Triangulation class for further details.

Supported input formats

At present, the following input formats are supported:

Structure of input grid data. The GridReordering class

It is your duty to use a correct numbering of vertices in the cell list, i.e. for lines in 1d, you have to first give the vertex with the lower coordinate value, then that with the higher coordinate value. For quadrilaterals in two dimensions, the vertex indices in the quad list have to be such that the vertices are numbered in counter-clockwise sense.

In two dimensions, another difficulty occurs, which has to do with the sense of a quadrilateral. A quad consists of four lines which have a direction, which is per definitionem as follows:

 *   3-->--2
 *   |     |
 *   ^     ^
 *   |     |
 *   0-->--1
 * 
Now, two adjacent cells must have a vertex numbering such that the direction of the common side is the same. For example, the following two quads
 *   3---4---5
 *   |   |   |
 *   0---1---2
 * 
may be characterised by the vertex numbers (0 1 4 3) and (1 2 5 4), since the middle line would get the direction 1->4 when viewed from both cells. The numbering (0 1 4 3) and (5 4 1 2) would not be allowed, since the left quad would give the common line the direction 1->4, while the right one would want to use 4->1, leading to an ambiguity. The Triangulation object is capable of detecting this special case, which can be eliminated by rotating the indices of the right quad by two. However, it would not know what to do if you gave the vertex indices (4 1 2 5), since then it would have to rotate by one element or three, the decision which to take is not yet implemented.

There are more ambiguous cases, where the triangulation may not know what to do at all without the use of sophisticated algorithms. Furthermore, similar problems exist in three space dimensions, where faces and lines have orientations that need to be taken care of.

For this reason, the read_* functions of this class that read in grids in various input formats call the GridReordering class to bring the order of vertices that define the cells into an ordering that satisfies the requiremenets of the Triangulation class. Be sure to read the documentation of that class if you experience unexpected problems when reading grids through this class.

Author:
Wolfgang Bangerth, 1998, 2000, Luca Heltai, 2004, 2007

Member Enumeration Documentation

template<int dim, int spacedim = dim>
enum GridIn::Format

List of possible mesh input formats. These values are used when calling the function read() in order to determine the actual reader to be called.

Enumerator:
Default  Use GridIn::default_format stored in this object.
ucd  Use read_ucd().
dbmesh  Use read_dbmesh().
xda  Use read_xda().
msh  Use read_msh().
netcdf  Use read_netcdf().
tecplot  Use read_tecplot().


Constructor & Destructor Documentation

template<int dim, int spacedim = dim>
GridIn< dim, spacedim >::GridIn (  ) 

Constructor.


Member Function Documentation

template<int dim, int spacedim = dim>
void GridIn< dim, spacedim >::attach_triangulation ( Triangulation< dim, spacedim > &  tria  ) 

Attach this triangulation to be fed with the grid data.

template<int dim, int spacedim = dim>
void GridIn< dim, spacedim >::read ( std::istream &  in,
Format  format = Default 
)

Read from the given stream. If no format is given, the default_format variable is used.

template<int dim, int spacedim = dim>
void GridIn< dim, spacedim >::read ( const std::string &  in,
Format  format = Default 
)

Open the file given by the string and call the previous function read(). This function uses the PathSearch mechanism to find files. The file class used is MESH.

template<int dim, int spacedim = dim>
void GridIn< dim, spacedim >::read_ucd ( std::istream &  in  ) 

Read grid data from an ucd file. Numerical data is ignored.

template<int dim, int spacedim = dim>
void GridIn< dim, spacedim >::read_dbmesh ( std::istream &  in  ) 

Read grid data from a file containing data in the DB mesh format.

template<int dim, int spacedim = dim>
void GridIn< dim, spacedim >::read_xda ( std::istream &  in  ) 

Read grid data from a file containing data in the XDA format.

template<int dim, int spacedim = dim>
void GridIn< dim, spacedim >::read_msh ( std::istream &  in  ) 

Read grid data from an msh file, either version 1 or version 2 of that file format. The GMSH formats are documented at http://www.geuz.org/gmsh/ .

Note:
The input function of deal.II does not distinguish between newline and other whitespace. Therefore, deal.II will be able to read files in a slightly more general format than Gmsh.

template<int dim, int spacedim = dim>
void GridIn< dim, spacedim >::read_netcdf ( const std::string &  filename  ) 

Read grid data from a NetCDF file. The only data format currently supported is the TAU grid format.

This function requires the library to be linked with the NetCDF library.

template<int dim, int spacedim = dim>
void GridIn< dim, spacedim >::read_tecplot ( std::istream &  in  ) 

Read grid data from a file containing tecplot ASCII data. This also works in the absence of any tecplot installation.

template<int dim, int spacedim = dim>
static std::string GridIn< dim, spacedim >::default_suffix ( const Format  format  )  [static]

Returns the standard suffix for a file in this format.

template<int dim, int spacedim = dim>
static Format GridIn< dim, spacedim >::parse_format ( const std::string &  format_name  )  [static]

Return the enum Format for the format name.

template<int dim, int spacedim = dim>
static std::string GridIn< dim, spacedim >::get_format_names (  )  [static]

Return a list of implemented input formats. The different names are separated by vertical bar signs (`|') as used by the ParameterHandler classes.

template<int dim, int spacedim = dim>
static void GridIn< dim, spacedim >::debug_output_grid ( const std::vector< CellData< dim > > &  cells,
const std::vector< Point< spacedim > > &  vertices,
std::ostream &  out 
) [static, protected]

This function can write the raw cell data objects created by the read_* functions in Gnuplot format to a stream. This is sometimes handy if one would like to see what actually was created, if it is known that the data is not correct in some way, but the Triangulation class refuses to generate a triangulation because of these errors. In particular, the output of this class writes out the cell numbers along with the direction of the faces of each cell. In particular the latter information is needed to verify whether the cell data objects follow the requirements of the ordering of cells and their faces, i.e. that all faces need to have unique directions and specified orientations with respect to neighboring cells (see the documentations to this class and the GridReordering class).

The output of this function consists of vectors for each line bounding the cells indicating the direction it has with respect to the orientation of this cell, and the cell number. The whole output is in a form such that it can be read in by Gnuplot and generate the full plot without further ado by the user.

template<int dim, int spacedim = dim>
static void GridIn< dim, spacedim >::skip_empty_lines ( std::istream &  in  )  [static, private]

Skip empty lines in the input stream, i.e. lines that contain either nothing or only whitespace.

template<int dim, int spacedim = dim>
static void GridIn< dim, spacedim >::skip_comment_lines ( std::istream &  in,
const char  comment_start 
) [static, private]

Skip lines of comment that start with the indicated character (e.g. #) following the point where the given input stream presently is. After the call to this function, the stream is at the start of the first line after the comment lines, or at the same position as before if there were no lines of comments.

template<int dim, int spacedim = dim>
static void GridIn< dim, spacedim >::parse_tecplot_header ( std::string &  header,
std::vector< unsigned int > &  tecplot2deal,
unsigned int n_vars,
unsigned int n_vertices,
unsigned int n_cells,
std::vector< unsigned int > &  IJK,
bool structured,
bool blocked 
) [static, private]

This function does the nasty work (due to very lax conventions and different versions of the tecplot format) of extracting the important parameters from a tecplot header, contained in the string header. The other variables are output variables, their value has no influence on the function execution..


Member Data Documentation

template<int dim, int spacedim = dim>
SmartPointer<Triangulation<dim,spacedim> > GridIn< dim, spacedim >::tria [protected]

Store address of the triangulation to be fed with the data read in.

template<int dim, int spacedim = dim>
Format GridIn< dim, spacedim >::default_format [private]

Input format used by read() if no format is given.


The documentation for this class was generated from the following file:

deal.II documentation generated on Sat Aug 15 16:52:01 2009 by doxygen 1.5.9