ContinentsOnGlobe.cpp

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/** @example ContinentsOnGlobe
 * Description: read a mesh on a sphere and boundaries of continents and major islands,
 * and write a boundaries mesh file (bound.vtk) and a file with sets for major continents
 * (map.h5m). Boundaries exist as 2 files, a list of boundary points and a list of loops,
 * representing each continent and major islands; there are 796 loops (islands). The first one has
 * 1239 edges/segments (Asia+Europe), while the last one has only 3. It must be a small island :)
 * ContinentsOnGlobe <input.h5m>
 * default values: poly2000.h5m : a mesh with 2000 polygons on a sphere of radius 1
 */
 
#include "moab/Core.hpp"
#include "moab/ReadUtilIface.hpp"
#include <cmath>
#include "moab/CartVect.hpp"
 
#include <iostream>
#include <fstream>
 
using namespace moab;
using namespace std;
 
string bd_name = string( MESH_DIR ) + string( "/../examples/earth/boundary_points.dat" );
string loops = string( MESH_DIR ) + string( "/../examples/earth/SaveLoopCounts" );
string input_file = string( MESH_DIR ) + string( "/../examples/earth/poly2000.h5m" );
 
double getLat( CartVect p )
{
 p.normalize();
 return asin( p[2] );
}
double getLon( CartVect p )
{
 p.normalize();
 double lon;
 
 lon = atan2( p[1], p[0] );
 
 if( lon < -2.95 )
 { // separate Asia/Europe from Americas
 return 2.0 * M_PI + lon;
 }
 else
 {
 return lon;
 }
}
 
// we project sphere points on a 2d map. We decide if a point is in interior of a loop
// with the span angle test; it will work for any island except Antarctica
 
bool interior_point( vector< double >& coords, int& startLoop, int& endLoop, double lat, double lon )
{
 // compute oriented angle between point and edges in the loop
 // if angle ~ +/-2Pi, it is in the interior
 double totalAngle = 0;
 for( int i = startLoop; i <= endLoop; i++ )
 {
 double x1 = coords[2 * i], y1 = coords[2 * i + 1];
 int i2 = i + 1;
 if( i == endLoop ) i2 = startLoop;
 double x2 = coords[2 * i2], y2 = coords[2 * i2 + 1];
 CartVect P1( x1 - lat, y1 - lon, 0. );
 CartVect P2( x2 - lat, y2 - lon, 0. );
 CartVect cross = P1 * P2;
 double angle1 = angle( P1, P2 );
 if( cross[2] < 0 ) angle1 = -angle1;
 totalAngle += angle1;
 }
 if( fabs( totalAngle + 2 * M_PI ) < 0.1 || fabs( totalAngle - 2 * M_PI ) < 0.1 ) return true;
 return false;
}
 
int main( int argc, char** argv )
{
 // Get MOAB instance
 Interface* mb = new( std::nothrow ) Core;
 if( NULL == mb ) return 1;
 
 if( argc > 1 )
 {
 // User has input file for mesh file
 input_file = argv[1];
 }
 
 cout << "input file : " << input_file << "\n";
 std::vector< double > coords;
 ifstream bdFile( bd_name.c_str() );
 if( !bdFile )
 {
 cout << endl << "Failed to open file " << bd_name << endl;
 ;
 return 1;
 }
 coords.resize( 0 );
 while( !bdFile.eof() )
 {
 double co;
 bdFile >> co;
 coords.push_back( co );
 }
 cout << " number of boundary points:" << coords.size() / 3 << "\n";
 /// get loops for boundaries
 vector< int > loopsindx;
 ifstream loopFile( loops.c_str() );
 while( !loopFile.eof() )
 {
 int indx;
 loopFile >> indx;
 loopsindx.push_back( indx );
 }
 cout << "number of loops: " << loopsindx.size() / 2 << "\n";
 // convert loops to lat-lon loops
 // it will be easier to determine in-out relations for points in 2d plane
 // careful with the international time zone; ( + - Pi longitude )
 vector< double > coords2d;
 coords2d.resize( coords.size() / 3 * 2 );
 for( int i = 0; i < (int)coords.size() / 3; i++ )
 {
 CartVect p( coords[3 * i], coords[3 * i + 1], coords[3 * i + 2] );
 coords2d[2 * i] = getLat( p );
 coords2d[2 * i + 1] = getLon( p );
 }
 
 ErrorCode rval = mb->load_file( input_file.c_str() );MB_CHK_SET_ERR( rval, "Can't load file" );
 // look at the center of element, and see if it is inside the loop
 
 Range cells;
 rval = mb->get_entities_by_dimension( 0, 2, cells );MB_CHK_SET_ERR( rval, "Can't get cells" );
 
 cout << "number of cells: " << cells.size() << "\n";
 
 // tag for continents
 Tag tag1;
 int defa = -1;
 rval = mb->tag_get_handle( "continent", 1, MB_TYPE_INTEGER, tag1, MB_TAG_DENSE | MB_TAG_CREAT, &defa );MB_CHK_SET_ERR( rval, "Trouble creating continent tag" );
 EntityHandle islandSets[6];
 for( int loop_index = 0; loop_index < 6; loop_index++ )
 {
 rval = mb->create_meshset( MESHSET_SET, islandSets[loop_index] );MB_CHK_SET_ERR( rval, "Can't create island set" );
 int startLoop = loopsindx[2 * loop_index];
 int endLoop = loopsindx[2 * loop_index + 1];
 
 vector< EntityHandle > interiorCells;
 for( Range::iterator cit = cells.begin(); cit != cells.end(); cit++ )
 {
 EntityHandle cell = *cit;
 // see if it is in the interior of the loop
 CartVect center;
 rval = mb->get_coords( &cell, 1, &( center[0] ) );MB_CHK_SET_ERR( rval, "Can't get cell center coords" );
 double lat = getLat( center ), lon = getLon( center );
 // if NA, use some boxes too, for lat/lon
 // if (NorthAmerica && (lat < 0.15 || lon < M_PI || lon > 2*M_PI - 0.5) )
 // continue;
 
 if( interior_point( coords2d, startLoop, endLoop, lat, lon ) )
 {
 interiorCells.push_back( cell );
 rval = mb->tag_set_data( tag1, &cell, 1, &loop_index );MB_CHK_SET_ERR( rval, "Can't get tag on cell" );
 }
 }
 
 rval = mb->add_entities( islandSets[loop_index], &interiorCells[0], interiorCells.size() );MB_CHK_SET_ERR( rval, "Can't add entities to set" );
 }
 
 std::stringstream islandFile;
 
 islandFile << "map.h5m";
 
 rval = mb->write_file( islandFile.str().c_str() );MB_CHK_SET_ERR( rval, "Can't write island file" );
 return 0;
}