ExtrudePoly.cpp

Description: read a 2d mesh in plane, extrude to form layers of prisms (polyhedra)
To run: ./ExtrudePoly [meshfile] [outfile] [nlayers] [thickness_layer]

/** @example ExtrudePoly.cpp
 * Description: read a 2d mesh in plane, extrude to form layers of prisms (polyhedra) \n
 *
 * To run: ./ExtrudePoly [meshfile] [outfile] [nlayers] [thickness_layer] \n
 */
 
#include "moab/Core.hpp"
#include "moab/ReadUtilIface.hpp"
#include <iostream>
 
using namespace moab;
using namespace std;
 
#ifndef MESH_DIR
#define MESH_DIR "."
#endif
 
// at most 20 edges per polygon
#define MAXEDGES 20
// Note: change the file name below to test a trivial "No such file or directory" error
string test_file_name = string( MESH_DIR ) + string( "/io/poly8-10.vtk" );
string output = string( "polyhedra.vtk" );
int layers = 1;
double layer_thick = 1.0;
 
int main( int argc, char** argv )
{
 // Get MOAB instance
 Interface* mb = new( std::nothrow ) Core;
 if( NULL == mb ) return 1;
 
 // Need option handling here for input filename
 if( argc > 1 )
 {
 // User has input a mesh file
 test_file_name = argv[1];
 }
 if( argc > 2 ) output = argv[2];
 
 if( argc > 3 ) layers = atoi( argv[3] );
 
 if( argc > 4 ) layer_thick = atof( argv[4] );
 
 std::cout << "Run: " << argv[0] << " " << test_file_name << " " << output << " " << layers << " " << layer_thick
 << "\n";
 // Load the mesh from vtk file
 ErrorCode rval = mb->load_mesh( test_file_name.c_str() );MB_CHK_ERR( rval );
 
 // Get verts entities, by type
 Range verts;
 rval = mb->get_entities_by_type( 0, MBVERTEX, verts );MB_CHK_ERR( rval );
 
 // Get faces, by dimension, so we stay generic to entity type
 Range faces;
 rval = mb->get_entities_by_dimension( 0, 2, faces );MB_CHK_ERR( rval );
 cout << "Number of vertices is " << verts.size() << endl;
 cout << "Number of faces is " << faces.size() << endl;
 
 Range edges;
 // create all edges
 rval = mb->get_adjacencies( faces, 1, true, edges, Interface::UNION );MB_CHK_ERR( rval );
 
 cout << "Number of edges is " << edges.size() << endl;
 
 std::vector< double > coords;
 int nvPerLayer = (int)verts.size();
 coords.resize( 3 * nvPerLayer );
 
 rval = mb->get_coords( verts, &coords[0] );MB_CHK_ERR( rval );
 // create first vertices
 Range* newVerts = new Range[layers + 1];
 newVerts[0] = verts; // just for convenience
 for( int ii = 0; ii < layers; ii++ )
 {
 for( int i = 0; i < nvPerLayer; i++ )
 coords[3 * i + 2] += layer_thick;
 
 rval = mb->create_vertices( &coords[0], nvPerLayer, newVerts[ii + 1] );MB_CHK_ERR( rval );
 }
 // for each edge, we will create layers quads
 int nquads = edges.size() * layers;
 ReadUtilIface* read_iface;
 rval = mb->query_interface( read_iface );MB_CHK_SET_ERR( rval, "Error in query_interface" );
 
 EntityHandle start_elem, *connect;
 // Create quads
 rval = read_iface->get_element_connect( nquads, 4, MBQUAD, 0, start_elem, connect );MB_CHK_SET_ERR( rval, "Error in get_element_connect" );
 int nedges = (int)edges.size();
 
 int indexConn = 0;
 for( int j = 0; j < nedges; j++ )
 {
 EntityHandle edge = edges[j];
 
 const EntityHandle* conn2 = NULL;
 int num_nodes;
 rval = mb->get_connectivity( edge, conn2, num_nodes );MB_CHK_ERR( rval );
 if( 2 != num_nodes ) MB_CHK_ERR( MB_FAILURE );
 
 int i0 = verts.index( conn2[0] );
 int i1 = verts.index( conn2[1] );
 for( int ii = 0; ii < layers; ii++ )
 {
 connect[indexConn++] = newVerts[ii][i0];
 connect[indexConn++] = newVerts[ii][i1];
 connect[indexConn++] = newVerts[ii + 1][i1];
 connect[indexConn++] = newVerts[ii + 1][i0];
 }
 }
 
 int nfaces = (int)faces.size();
 EntityHandle* allPolygons = new EntityHandle[nfaces * ( layers + 1 )];
 for( int i = 0; i < nfaces; i++ )
 allPolygons[i] = faces[i];
 
 // vertices are parallel to the base vertices
 int indexVerts[MAXEDGES] = { 0 }; // polygons with at most MAXEDGES edges
 EntityHandle newConn[MAXEDGES] = { 0 };
 EntityHandle polyhedronConn[MAXEDGES + 2] = { 0 };
 
 // edges will be used to determine the lateral faces of polyhedra (prisms)
 int indexEdges[MAXEDGES] = { 0 }; // index of edges in base polygon
 for( int j = 0; j < nfaces; j++ )
 {
 EntityHandle polyg = faces[j];
 
 const EntityHandle* connp = NULL;
 int num_nodes;
 rval = mb->get_connectivity( polyg, connp, num_nodes );MB_CHK_ERR( rval );
 
 for( int i = 0; i < num_nodes; i++ )
 {
 indexVerts[i] = verts.index( connp[i] );
 int i1 = ( i + 1 ) % num_nodes;
 EntityHandle edgeVerts[2] = { connp[i], connp[i1] };
 // get edge adjacent to these vertices
 Range adjEdges;
 rval = mb->get_adjacencies( edgeVerts, 2, 1, false, adjEdges );MB_CHK_ERR( rval );
 if( adjEdges.size() < 1 ) MB_CHK_SET_ERR( MB_FAILURE, " did not find edge " );
 indexEdges[i] = edges.index( adjEdges[0] );
 if( indexEdges[i] < 0 ) MB_CHK_SET_ERR( MB_FAILURE, "did not find edge in range" );
 }
 
 for( int ii = 0; ii < layers; ii++ )
 {
 // create a polygon on each layer
 for( int i = 0; i < num_nodes; i++ )
 newConn[i] = newVerts[ii + 1][indexVerts[i]]; // vertices in layer ii+1
 
 rval = mb->create_element( MBPOLYGON, newConn, num_nodes, allPolygons[nfaces * ( ii + 1 ) + j] );MB_CHK_ERR( rval );
 
 // now create a polyhedra with top, bottom and lateral swept faces
 // first face is the bottom
 polyhedronConn[0] = allPolygons[nfaces * ii + j];
 // second face is the top
 polyhedronConn[1] = allPolygons[nfaces * ( ii + 1 ) + j];
 // next add lateral quads, in order of edges, using the start_elem
 // first layer of quads has EntityHandle from start_elem to start_elem+nedges-1
 // second layer of quads has EntityHandle from start_elem + nedges to
 // start_elem+2*nedges-1 ,etc
 for( int i = 0; i < num_nodes; i++ )
 {
 polyhedronConn[2 + i] = start_elem + ii + layers * indexEdges[i];
 }
 // Create polyhedron
 EntityHandle polyhedron;
 rval = mb->create_element( MBPOLYHEDRON, polyhedronConn, 2 + num_nodes, polyhedron );MB_CHK_ERR( rval );
 }
 }
 rval = mb->write_file( output.c_str() );MB_CHK_ERR( rval );
 
 delete mb;
 
 return 0;
}