CGAL users discussion list

[Laurent Rineau <>]

On Thursday 04 December 2008 17:42:07 

 wrote:
> Hi,
>
> I am a newbie to CGAL. I was writing a code to access OFF files. I am not
> able to access the properties of mesh. Could some one please point out
> where I am making the mistake.
>
> #include <CGAL/Simple_cartesian.h>
> #include <CGAL/Polyhedron_3.h>
> #include <CGAL/IO/Polyhedron_iostream.h>
>
> #include <iostream>
> #include <istream>
> #include <fstream>
>
> typedef CGAL::Simple_cartesian<double> Kernel;
> typedef CGAL::Polyhedron_3<Kernel>     Polyhedron;
>
> int main() {
>     std::ifstream stream("test.off");
>     Polyhedron P;
>     stream >> P;
>     std::cout << "\n "<<P.size_of_vertices();
>     return 0;
> }

The correct code is that one:

int main() {
    std::ifstream stream("test.off");
    if(!stream} {
      std::cerr << "Cannot open file!\n";
      return 1;
    }
    Polyhedron P;
    stream >> P;
    if(!stream} {
      std::cerr << "test.off is not a polyhedron\n";
      return 1;
    }
    std::cout << "\n "<<P.size_of_vertices();
    return 0;
}

That is: you need to test the good() bits of the stream *after* the attempt 
to 
read a polyhedron from it.

Most probably you OFF file does not correspond to a manifold *and oriented* 
mesh (with optional boundaries). You need to orient your off before trying to 
read it to a polyhedron.

-- 
Laurent Rineau, PhD
Engineer at GeometryFactory
http://www.geometryfactory.com/