mbex3.cpp

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/// \file mbex3.cpp
///
/// \author Milad Fatenejad
///
/// \brief beginner tutorial, example 3: Demonstrates
/// constructing/saving a simple 2x2x2 hex mesh using the
/// structured mesh interface
///
/// In this example, we create a 2x2x2 mesh that is identical to the
/// previous example. However, in this case we will use the structured
/// mesh interface since the mesh we created is logically
/// structured. There are many advantages to using the structured mesh
/// interface...such as memory savings, speed, ease-of-use...
///
/// In the previous example, we had to create 27 vertexes manually,
/// define the connectivity, then manually create 8 hexahedrons. With
/// the structured mesh interface, we just have to create the 27
/// vertexes then tell MOAB that these define a 2x2x2 structured mesh
/// and everything else is taken care of for us!
 
// The moab/Core.hpp header file is needed for all MOAB work...
#include "moab/Core.hpp"
 
// The moab/ScdInterface.hpp contains code which defines the moab
// structured mesh interface
#include "moab/ScdInterface.hpp"
 
#include <iostream>
 
// ****************
// * *
// * main *
// * *
// ****************
int main()
{
 moab::ErrorCode rval;
 moab::Core mbint;
 
 // **********************************
 // * Create the Structured Mesh *
 // **********************************
 
 // As before, we have to create an array defining the coordinate of
 // each vertex:
 const unsigned NUMVTX = 27;
 const double vertex_coords[3 * NUMVTX] = {
 0, 0, 0, 1, 0, 0, 2, 0, 0, 0, 1, 0, 1, 1, 0, 2, 1, 0, 0, 2, 0, 1, 2, 0, 2, 2, 0,
 
 0, 0, 1, 1, 0, 1, 2, 0, 1, 0, 1, 1, 1, 1, 1, 2, 1, 1, 0, 2, 1, 1, 2, 1, 2, 2, 1,
 
 0, 0, 2, 1, 0, 2, 2, 0, 2, 0, 1, 2, 1, 1, 2, 2, 1, 2, 0, 2, 2, 1, 2, 2, 2, 2, 2 };
 
 // moab::ScdInterface is the structured mesh interface class for
 // MOAB.
 moab::ScdInterface* scdint;
 
 // The query_interface method will create a structured mesh instance
 // for mbcore and will point scdint to it. This is how you tell moab
 // that our moab::Core instance is going to represent a structured
 // mesh.
 rval = mbint.query_interface( scdint );MB_CHK_SET_ERR( rval, "mbint.query_interface failed" );
 
 // Structured meshes a divided into "boxes". Each box represents a
 // little structured mesh. A single mesh, for example a
 // block-structured mesh, can contain many individual boxes. In this
 // example, we want to create a single, 2x2x2 box. The construct_box
 // method will do this for us.
 moab::ScdBox* scdbox = NULL;
 rval = scdint->construct_box( moab::HomCoord( 0, 0, 0 ), moab::HomCoord( 2, 2, 2 ), vertex_coords, NUMVTX, scdbox );MB_CHK_SET_ERR( rval, "scdint->construct_box failed" );
 
 // moab::HomCoord is a little class that is used to represent a
 // coordinate in logical space. Above, we told MOAB that we want
 // indexes which extend from 0,0,0 to 2,2,2 for vertexes. Since the
 // i,j,k start/end indexes are all different, MOAB knows that our
 // mesh consists of hexes. If we had gone from 0,0,0 to 1,1,0 then
 // MOAB would construct a 2x2x1 mesh of quadrilaterals.
 
 // ***************
 // * Inspect *
 // ***************
 
 // Our mesh now exists and contains a single box! Lets loop over
 // that box and manually print out the handle of each vertex/hex:
 unsigned i, j, k;
 
 // Print out the entity handle associated with each hex:
 for( i = 0; i < 2; ++i )
 for( j = 0; j < 2; ++j )
 for( k = 0; k < 2; ++k )
 {
 std::cout << "Hex (" << i << "," << j << "," << k << ") "
 << "has handle: " << scdbox->get_element( i, j, k ) << std::endl;
 }
 
 // Print out the entity handle associated with each vertex:
 for( i = 0; i < 3; ++i )
 for( j = 0; j < 3; ++j )
 for( k = 0; k < 3; ++k )
 {
 std::cout << "Vertex (" << i << "," << j << "," << k << ") "
 << "has handle: " << scdbox->get_vertex( i, j, k ) << std::endl;
 }
 
 // Of course, you can still use all of the functionality defined in
 // mbint to get coordinates, connectivity, etc...
 
 // ***************************
 // * Write Mesh to Files *
 // ***************************
 rval = mbint.write_file( "mbex3.vtk" );MB_CHK_SET_ERR( rval, "write_file(mbex3.vtk) failed" );
 
 return 0;
}