SurfArea.cpp File Reference

#include "moab/Core.hpp"
#include "moab/Range.hpp"
#include "moab/CartVect.hpp"
#include <iostream>

Go to the source code of this file.

Functions
double	compute_area (std::vector< EntityHandle > &)
int	main (int argc, char **argv)
Variables
Interface *	mb

---

Function Documentation

double compute_area

(

std::vector< EntityHandle > &

entities

)

Definition at line 92 of file SurfArea.cpp.

                                                       {
 
  ErrorCode rval= MB_SUCCESS;
  double area = 0.0;
 
  // loop thro' all the elements
  for (int i=0;i<int(entities.size());i++){
    std::vector<EntityHandle> conn;
    EntityHandle handle = entities[i];

    // get the connectivity of this element
    rval = mb->get_connectivity(&handle, 1, conn);
    if (MB_SUCCESS != rval) return -1.0;

    // break polygon into triangles and sum the area - Limitation: Convex polygon
    for (int j = 2; j<=int(conn.size()); ++j){

      EntityHandle vertices[3]={conn[0], conn[j-1],  conn[j-2]};
      CartVect coords[3];
      
      // get 3 coordinates forming the triangle
      rval = mb->get_coords(vertices, 3, coords[0].array());
      if (MB_SUCCESS != rval) return -1.0;
      
      CartVect edge0 = coords[1] - coords [0];
      CartVect edge1 = coords [2] - coords[0];
      
      // using MBCarVect overloaded operators and computing triangle area
      area+=(edge0*edge1).length()/2.0;
    }
  }
  // clear the entities, else old entities remain
  entities.clear();
  return area;
}

int main	(	int	argc,
		char **	argv
	)

Definition at line 22 of file SurfArea.cpp.

                                {
  if (1 == argc) {
    std::cout << "Usage: " << argv[0] << " <filename>" << std::endl;
    return 0;
  }
  
  // declare variables
  Tag gtag, idtag;
  ErrorCode rval;
  const char *tag_geom = "GEOM_DIMENSION";
  const char *tag_gid = "GLOBAL_ID";
  Range sets;
  std::vector<EntityHandle> ents;
  
  // load a file
  mb = new Core();
  rval = mb->load_file(argv[1]);
  if (MB_SUCCESS != rval) return 1;

  // get the tag handle for the tags
  rval = mb->tag_get_handle(tag_geom, 1, MB_TYPE_INTEGER, gtag);
  if (MB_SUCCESS != rval) return 1;
  rval = mb->tag_get_handle(tag_gid, 1, MB_TYPE_INTEGER, idtag);
  if (MB_SUCCESS != rval) return 1;

  // get all the sets with GEOM_DIMESION tag
  rval = mb->get_entities_by_type_and_tag(0, MBENTITYSET, &gtag,
                      NULL, 1, sets);
  if (MB_SUCCESS != rval) return 1;
 
  // iterate over each set, getting entities
  Range::iterator set_it;
    
  // loop thru all the geometric entity sets
  for (set_it = sets.begin(); set_it != sets.end(); set_it++)  {

    EntityHandle this_set = *set_it;
    
    // get the id for this set
    int set_id;
    rval = mb->tag_get_data(gtag, &this_set, 1, &set_id);
    if (MB_SUCCESS != rval) return 1;

    // check if it is a surface entities (GEOM_DIMENSION 2) then compute area
    if (set_id ==2){
      
      // area of a surface
      double total_area=0.0;

      //get the global id of this surface
      int gid = 0;
      rval = mb->tag_get_data(idtag, &this_set, 1, &gid);
      if (MB_SUCCESS != rval) return 1;

      // get all entities with dimension 2 in ents
      rval = mb->get_entities_by_dimension(this_set, 2, ents);
      if (MB_SUCCESS != rval) return 1;
 
      // compute the area
      total_area = compute_area(ents);

      ents.clear();
      
      std::cout << "Total area of meshes in surface " << gid << " =  " << total_area << std::endl;
    }
  }
}

---

Variable Documentation

Interface* mb

Definition at line 20 of file SurfArea.cpp.