Mesh Oriented datABase  (version 5.5.1)
An array-based unstructured mesh library
ComputeTriDual.cpp

Compute the polygonal (dual) mesh of the primal simplex grid in 2-D.
To run: ComputeTriDual input_file output_file
An example to demonstrate computing the dual polygonal grid of a triangulation on a spherical surface.

/** @example ComputeTriDual.cpp \n
* \brief Compute the polygonal (dual) mesh of the primal simplex grid in 2-D. \n
* <b>To run</b>: ComputeTriDual input_file output_file \n
* An example to demonstrate computing the dual polygonal grid of a triangulation
* on a spherical surface.
*/
#include <iostream>
#include <vector>
// Include header for MOAB instance and tag conventions for
#include "moab/Range.hpp"
#include "moab/Core.hpp"
#ifdef MOAB_HAVE_MPI
#endif
///////////////////////////////////////////////////////////////////////////////
{
moab::Range verts;
rval = mb->get_connectivity( cells, verts );MB_CHK_SET_ERR( rval, "Failed to get connectivity" );
rval = mb->query_interface( iface );MB_CHK_SET_ERR( rval, "Can't get reader interface" );
std::vector< double* > ccenters;
rval = iface->get_node_coords( 3, cells.size(), 0, startv, ccenters );MB_CHK_SET_ERR( rval, "Can't get node coords" );
moab::Tag gidTag = mb->globalId_tag();
std::vector< int > gids( cells.size() );
rval = mb->get_coords( cells, ccenters[0], ccenters[1], ccenters[2] );MB_CHK_SET_ERR( rval, "Failed to get coordinates" );
rval = mb->tag_get_data( gidTag, cells, &gids[0] );MB_CHK_SET_ERR( rval, "Can't set global_id tag" );
moab::Range dualverts( startv, startv + cells.size() - 1 );
rval = mb->add_entities( dual_set, dualverts );MB_CHK_SET_ERR( rval, "Can't add entities" );
rval = mb->tag_set_data( gidTag, dualverts, &gids[0] );MB_CHK_SET_ERR( rval, "Can't set global_id tag" );
#define CC( ind ) moab::CartVect( ccenters[0][ind], ccenters[1][ind], ccenters[2][ind] )
#define CCXMY( ind, cv ) \
moab::CartVect( ccenters[0][ind] - ( cv )[0], ccenters[1][ind] - ( cv )[1], ccenters[2][ind] - ( cv )[2] )
const moab::EntityHandle svtx = *( cells.begin() );
// maintain block-wise polygon elements
moab::Range dualcells;
std::map< size_t, std::vector< moab::EntityHandle > > polygonConn;
// Generate new Face array
for( moab::Range::iterator vit = verts.begin(); vit != verts.end(); ++vit )
{
moab::EntityHandle vtx = *vit;
std::vector< moab::EntityHandle > adjs;
// generate all required adjacencies
rval = mb->get_adjacencies( &vtx, 1, 2, true, adjs );MB_CHK_SET_ERR( rval, "Failed to get adjacencies" );
const size_t nEdges = adjs.size();
double vxyz[3];
rval = mb->get_coords( &vtx, 1, vxyz );MB_CHK_SET_ERR( rval, "Failed to get coordinates" );
// Reorient Faces
moab::CartVect nodeCentral( vxyz );
moab::CartVect noderef = CC( adjs[0] - svtx );
moab::CartVect node0 = noderef - nodeCentral;
double dNode0Mag = node0.length();
moab::CartVect nodeCross = noderef * nodeCentral;
// Determine the angles about the central Node of each Face Node
std::vector< double > dAngles;
dAngles.resize( nEdges );
dAngles[0] = 0.0;
for( size_t j = 1; j < nEdges; j++ )
{
moab::CartVect nodeDiff = CCXMY( adjs[j] - svtx, nodeCentral );
double dNodeDiffMag = nodeDiff.length();
double dSide = nodeCross % nodeDiff;
double dDotNorm = ( node0 % nodeDiff ) / ( dNode0Mag * dNodeDiffMag );
// double dAngle;
if( dDotNorm > 1.0 )
{
dDotNorm = 1.0;
}
dAngles[j] = acos( dDotNorm );
if( dSide > 0.0 )
{
dAngles[j] = -dAngles[j] + 2.0 * M_PI;
}
}
std::vector< moab::EntityHandle >& face = polygonConn[nEdges];
if( face.size() == 0 ) face.reserve( nEdges * verts.size() / 4 );
face.push_back( dualverts[adjs[0] - svtx] );
// Orient each Face by putting Nodes in order of increasing angle
double dCurrentAngle = 0.0;
for( size_t j = 1; j < nEdges; j++ )
{
int ixNextNode = 1;
double dNextAngle = 2.0 * M_PI;
for( size_t k = 1; k < nEdges; k++ )
{
if( ( dAngles[k] > dCurrentAngle ) && ( dAngles[k] < dNextAngle ) )
{
ixNextNode = k;
dNextAngle = dAngles[k];
}
}
face.push_back( dualverts[adjs[ixNextNode] - svtx] );
dCurrentAngle = dNextAngle;
}
}
std::map< size_t, std::vector< moab::EntityHandle > >::iterator eit;
for( eit = polygonConn.begin(); eit != polygonConn.end(); ++eit )
{
const size_t nVPerE = eit->first;
const size_t nElePerType = static_cast< int >( eit->second.size() / nVPerE );
moab::EntityHandle starte; // Connectivity
rval = iface->get_element_connect( nElePerType, eit->first, moab::MBPOLYGON, 0, starte, conn );MB_CHK_SET_ERR( rval, "Can't get element connectivity" );
// copy the connectivity that we have accumulated
std::copy( eit->second.begin(), eit->second.end(), conn );
eit->second.clear();
// add this polygon sequence to the aggregate data
moab::Range mbcells( starte, starte + nElePerType - 1 );
dualcells.merge( mbcells );
}
// add the computed dual cells to mesh
rval = mb->add_entities( dual_set, dualcells );MB_CHK_SET_ERR( rval, "Can't add polygonal entities" );
// Assign global IDs to all the dual cells - same as original vertices
assert( dualcells.size() == verts.size() );
gids.resize( verts.size() );
rval = mb->tag_get_data( gidTag, verts, &gids[0] );MB_CHK_SET_ERR( rval, "Can't set global_id tag" );
if( gids[0] == gids[1] && gids[0] < 0 )
{
#ifdef MOAB_HAVE_MPI
moab::ParallelComm pcomm( mb, MPI_COMM_WORLD );
rval = pcomm.assign_global_ids( dual_set, 2, 1, false, true, true );MB_CHK_SET_ERR( rval, "Can't assign global_ids" );
#else
// No global ID assigned to input vertices.
// Can we use std::iota ??
for( size_t ix = 0; ix < gids.size(); ++ix )
gids[ix] = ix + 1;
// set GID tag
rval = mb->tag_set_data( gidTag, dualcells, &gids[0] );MB_CHK_SET_ERR( rval, "Can't set global_id tag" );
std::cout << "GIDs: " << gids[0] << " " << gids[1] << " " << gids[2] << " " << gids[3] << " " << gids[4] << " "
<< gids[5] << "\n";
#endif
}
gids.clear();
// delete the original entities from the mesh
rval = mb->delete_entities( cells );MB_CHK_SET_ERR( rval, "Can't remove entities" );
rval = mb->delete_entities( verts );MB_CHK_SET_ERR( rval, "Can't remove entities" );
}
///////////////////////////////////////////////////////////////////////////////
int main( int argc, char** argv )
{
// Get MOAB instance
moab::Interface* mb = new( std::nothrow ) moab::Core;
if( NULL == mb ) return 1;
std::string inputFile = std::string( MESH_DIR ) + "/globalmpas_deltri.h5m";
opts.addOpt< std::string >( "inFile,i", "Specify the input file name string ", &inputFile );
#ifdef MOAB_HAVE_HDF5
std::string outputFile = "outDualMesh.h5m";
#else
std::string outputFile = "outDualMesh.vtk";
#endif
opts.addOpt< std::string >( "outFile,o", "Specify the input file name string ", &outputFile );
opts.parseCommandLine( argc, argv );
moab::EntityHandle triangle_set, dual_set;
rval = mb->create_meshset( moab::MESHSET_SET, triangle_set );MB_CHK_SET_ERR( rval, "Can't create new set" );
rval = mb->create_meshset( moab::MESHSET_SET, dual_set );MB_CHK_SET_ERR( rval, "Can't create new set" );
// This file is in the mesh files directory
const char* readopts = "";
rval = mb->load_file( inputFile.c_str(), &triangle_set, readopts );MB_CHK_SET_ERR( rval, "Failed to read" );
// get all cells of dimension 2;
moab::Range cells;
rval = mb->get_entities_by_dimension( triangle_set, 2, cells );MB_CHK_SET_ERR( rval, "Failed to get cells" );
std::cout << "Original number of triangular cells : " << cells.size() << "\n";
// call the routine to compute the dual grid
rval = compute_dual_mesh( mb, dual_set, cells );MB_CHK_SET_ERR( rval, "Failed to compute dual mesh" );
// write the mesh to disk
rval = mb->write_file( outputFile.c_str() );MB_CHK_SET_ERR( rval, "Failed to write new file" );
cells.clear();
rval = mb->get_entities_by_dimension( dual_set, 2, cells );MB_CHK_SET_ERR( rval, "Failed to get cells" );
std::cout << "Wrote the dual mesh: " << outputFile << " containing " << cells.size() << " polygonal cells\n";
delete mb;
return 0;
}