CGAL users discussion list

[Laurent Rineau <>]

On Thursday 24 May 2007 04:54:55 

 wrote:
> Dear Laurent,
>
> Thanks for your answer.
>
> > All the surfacic information are in the object c2t3. See the
> > documentation, for that class:
>
> I managed to get the surfacic information.
> But I am not sure why facet iterator variable for c2t3 does not work
> without initializing it.
>
> If I try to compile the following fragment of code,
> C2t3::Facet_iterator it;
> the compiler (VC7) complains like
> "error C2512:
> 'CGAL::Complex_2_in_triangulation_3<Tr>::Iterator_not_in_complex' ". On the
> other hand, the following one can be compiled without any claims
> C2t3::Facet_iterator it = c2t3.facets_begin();
> Am I doing something wrong?

In way, yes: you should not used uninitialized iterators. On the other hand, 
the "iterator" concept of the STL states that iterator types should have a 
default constructor.

If you really want to construct uninitialized C2t3::Facet_iterator objects, 
apply the following patch (not tested).

--- include/CGAL/Complex_2_in_triangulation_3.h 2007-05-24 09:31:33.000000000 
+0200
+++ include/CGAL/Complex_2_in_triangulation_3.h 2007-05-24 09:31:29.000000000 
+0200
@@ -167,13 +167,16 @@
   class Iterator_not_in_complex {
     Self* self;
   public:
-    Iterator_not_in_complex(Self* self) : self(self) 
+    Iterator_not_in_complex(Self* self = 0) : self(self) 
     {
     }
     
     template <typename Iterator> // Facet or Edges iterators
     bool operator()(Iterator it) const {
-      return ! self->is_in_complex(*it);
+      if(self)
+       return ! self->is_in_complex(*it);
+      else
+       return true;
     }
   }; // end struct Iterator_not_in_complex
 

> > If you want to recreate a surface from a set of points, you need a
> > surface reconstruction algorithm. As far as I know, the only one that is
> > publicly available in CGAL is the alpha shape.
>
> Could the reconstructed shape be input for the function make_surface_mesh?

No. The reconstructed shape already is a kind of surface mesh. What do you 
want to achieve? Re-mesh it?

> or do we have another way to make surface mesh from the shape?

Surface_mesher should be able to mesh implicit surfaces defined by a set of 
point, if one provides an implicit function that approximates the surface. 
However, such functionality is not implementated in CGAL.

> My goal is to create surface mesh from given points written in a file.
> I think one way to do that is to convert the file format to INRIMAGE, GIS
> or ANALYZE one if their file format opens.

INRIMAGE, GIS or ANALYZE are 3D images file formats, that is a 3D grid (for 
example 256×256×256), that has a float value at each voxel. You cannot 
convert a set of point into a 3D image.

-- 
Laurent Rineau
INRIA - Sophia Antipolis
BP 93, 2004 Route des Lucioles
06902 Sophia Antipolis Cedex FRANCE