CGAL users discussion list

[Merlin Etzold <>]

Dear Andreas,

Thank you very much for your reply - I will try it out tomorrow. I have a question: I would have never worked that out for myself - is there any reference (which I have obviously missed so far) where the underlying design ideas are explained?

Thank you very much and best wishes,

Merlin :)

Merlin A. Etzold, PhD

24 Oyster Row

Cambridge

CB5 8LJ

United Kindgom
+44 7851 467997

On 6 April 2016 at 15:26, Andreas Fabri <> wrote:

The Polyhedron does not allow to directly change coordinates.

You can do it with the help of property maps.
A property map is something for that there are
global functions get and put to acces, for example,
the point property of a vertex.

This is used systematically in the Polygon Mesh
Processing, package, so learning how to use them
for the simple problem you want to solve, will
save you time later.


#include <CGAL/Simple_cartesian.h>
#include <CGAL/Polyhedron_3.h>
#include <CGAL/IO/Polyhedron_iostream.h>
#include <CGAL/boost/graph/graph_traits_Polyhedron_3.h>
#include <CGAL/boost/graph/properties_Polyhedron_3.h>
#include <fstream>

typedef CGAL::Simple_cartesian<double> Kernel;
typedef Kernel::Point_3                Point_3;
typedef CGAL::Polyhedron_3<Kernel>     Polyhedron;

typedef boost::graph_traits<Polyhedron> GraphTraits;
typedef GraphTraits::vertex_descriptor vertex_descriptor;

int main(int, char** argv)
{
  std::ifstream in(argv[1]);
  Polyhedron P;
  in >> P;


  // First obtain the type of the property map:
  typedef boost::property_map<Polyhedron, CGAL::vertex_point_t>::type PM;

  // Then obtain the property map for P
  PM coord = get(CGAL::vertex_point,P);

  BOOST_FOREACH(vertex_descriptor vd, vertices(P)){
    // Now access the property
    Point_3 p =  get(coord, vd);
    p = p + (p - CGAL::ORIGIN);
    put(coord, vd, p);
  }
  BOOST_FOREACH(vertex_descriptor vd, vertices(P)){
    std::cout << get(coord, vd) << std::endl;
  }
  return 0;

}



On 06/04/2016 16:06, Merlin Etzold wrote:

Dear All,

Sorry if this is a duplication - I tried to ask the question previously
as a follow-on to another question:

I have a Polyhedron_3 and want to alter the position of individual
vertices to distort the shape. However, I have not found a way how to
actually change the vertex coordinates - only how to read them out. Help
would be much appreciated.

Thank you and best wishes,
Merlin :)


Merlin A. Etzold, PhD
24 Oyster Row
Cambridge
CB5 8LJ
United Kindgom
+44 7851 467997

--
Andreas Fabri, PhD
Chief Officer, GeometryFactory
Editor, The CGAL Project

phone: +33.492.954.912    skype: andreas.fabri

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