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

Merge vertices in 2d cell, if they are repeated
To run: QuadTriConv input_file output_file

In this example, a mesh that has vertices repeated due to south or north pole, for example in an rll mesh, need to be converted to triangles, preserving GLOBAL_ID tag

/** @example QuadTriConv.cpp \n
* \brief Merge vertices in 2d cell, if they are repeated \n
* <b>To run</b>: QuadTriConv input_file output_file \n
*
* In this example, a mesh that has vertices repeated due to south or north pole, for
* example in an rll mesh, need to be converted to triangles, preserving GLOBAL_ID tag
*/
#include <iostream>
#include <vector>
//#include <string>
// Include header for MOAB instance and tag conventions for
#include "moab/Core.hpp"
using namespace moab;
using namespace std;
int main( int argc, char** argv )
{
// Get MOAB instance
Interface* mb = new( std::nothrow ) Core;
if( NULL == mb ) return 1;
std::string filename, outfile;
outfile = string( "out.h5m" );
if( argc == 1 ) return 0;
if( argc > 1 ) filename = string( argv[1] );
if( argc > 2 ) outfile = string( argv[2] );
// This file is in the mesh files directory
ErrorCode rval = mb->load_file( filename.c_str() );MB_CHK_SET_ERR( rval, "Failed to read" );
// get all cells of dimension 2;
Range cells;
rval = mb->get_entities_by_dimension( 0, 2, cells );MB_CHK_SET_ERR( rval, "Failed to get cells" );
cout << " number of cells : " << cells.size() << "\n";
Tag gid; // global id tag
rval = mb->tag_get_handle( "GLOBAL_ID", gid );MB_CHK_SET_ERR( rval, "Failed to get Global ID tag" );
Range modifiedCells; // will be deleted at the end; keep the gid
for( Range::iterator cit = cells.begin(); cit != cells.end(); cit++ )
{
EntityHandle cell = *cit;
const EntityHandle* connec = NULL;
int num_verts = 0;
rval = mb->get_connectivity( cell, connec, num_verts );MB_CHK_SET_ERR( rval, "Failed to get connectivity" );
vector< EntityHandle > newConnec;
newConnec.push_back( connec[0] ); // at least one vertex
int index = 0;
int new_size = 1;
while( index < num_verts - 2 )
{
int next_index = ( index + 1 );
if( connec[next_index] != newConnec[new_size - 1] )
{
newConnec.push_back( connec[next_index] );
new_size++;
}
index++;
}
// add the last one only if different from previous and first node
if( ( connec[num_verts - 1] != connec[num_verts - 2] ) && ( connec[num_verts - 1] != connec[0] ) )
{
newConnec.push_back( connec[num_verts - 1] );
new_size++;
}
if( new_size < num_verts )
{
// cout << "new cell from " << cell << " has only " << new_size << " vertices \n";
modifiedCells.insert( cell );
// create a new cell with type triangle, quad or polygon
EntityType type = MBTRI;
if( new_size == 3 )
type = MBTRI;
else if( new_size == 4 )
type = MBQUAD;
else if( new_size > 4 )
type = MBPOLYGON;
// create new cell
EntityHandle newCell;
rval = mb->create_element( type, &newConnec[0], new_size, newCell );MB_CHK_SET_ERR( rval, "Failed to create new cell" );
// set the old id to the new element
int id;
rval = mb->tag_get_data( gid, &cell, 1, &id );MB_CHK_SET_ERR( rval, "Failed to get global id" );
rval = mb->tag_set_data( gid, &newCell, 1, &id );MB_CHK_SET_ERR( rval, "Failed to set global id on new cell" );
}
}
mb->delete_entities( modifiedCells );
// in case global ids are not set for vertices, set them, in order;
// they are needed for migrating later on
//
Range verts;
rval = mb->get_entities_by_dimension( 0, 0, verts );MB_CHK_SET_ERR( rval, "Failed to get vertices" );
vector< int > gids;
gids.resize( verts.size() );
rval = mb->tag_get_data( gid, verts, &gids[0] );MB_CHK_SET_ERR( rval, "Failed to get gids on vertices" );
if( gids[0] <= 0 )
{
// gids were never set, assign them
for( size_t i = 1; i <= verts.size(); i++ )
gids[i - 1] = (int)i;
rval = mb->tag_set_data( gid, verts, &gids[0] );MB_CHK_SET_ERR( rval, "Failed to set gids on vertices" );
}
rval = mb->write_file( outfile.c_str() );MB_CHK_SET_ERR( rval, "Failed to write new file" );
cout << " wrote file " << outfile << " with " << modifiedCells.size() << " modified cells\n";
delete mb;
return 0;
}