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"
#include "MBTagConventions.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;
}