CGAL users discussion list

["Laurent Rineau (CGAL/GeometryFactory)" <>]

Le Friday 27 March 2015 04:36:27 misterdan a écrit :
> I'm trying to make a 3D mesh from a segmented 3D cardiac image, which is
> very similar to the example shown in the documentation.
> http://doc.cgal.org/latest/Mesh_3/Mesh_3_2mesh_3D_image_8cpp-example.html
> <http://doc.cgal.org/latest/Mesh_3/Mesh_3_2mesh_3D_image_8cpp-example.html>
> 
> However, the program could not produce any mesh from my image, it stuck in
> the meshing process for very long time, and I had no choice but to terminate
> the program manually.
> My input image is a binary image, with value 0 or 255.
> I have checked that the program did indeed read my image successfully (it
> shows the correct image dimension)
> 
> I have tried different parameters and it still stuck in the meshing process.
> Any useful suggestion ?
> Thank you very much.
> I attach the image below for your reference. (it's in inr.gz format...)
> Mask.gz <http://cgal-discuss.949826.n4.nabble.com/file/n4660606/Mask.gz>

Hi,

The image Mask.gz is labellized, but its data type is `double`. By default, 
the class template `CGAL::Labeled_image_mesh_domain_3` only deal with 
labellized image whose data type is 8 bits (signed or not, that makes no 
difference).

Two options:
  - you can recreate the image Mask.gz, so that the data type is 'unsigned 
char',
  - you can try non-default options of CGAL classes, that honestly have not 
been tested for years.

For the second option, see the declaration of that class template:

    template<class Image,
             class BGT,
             class Wrapper = Mesh_3::Image_to_labeled_function_wrapper<Image, 
BGT> >
    class Labeled_image_mesh_domain_3;

The third parameter is `Wrapper`, and its default argument is:

    CGAL:: Mesh_3::Image_to_labeled_function_wrapper<Image, BGT>

See now the declaration of `Image_to_labeled_function_wrapper`, in 
<CGAL/Mesh_3/Image_to_labeled_function_wrapper.h>:

    template<class Image_,
             class BGT,
             typename Image_word_type = unsigned char,
             typename Return_type = int,
             bool use_trilinear_interpolation=true>
    class Image_to_labeled_function_wrapper

You can see that, by default, the data type (here named `Image_word_type`) is 
`unsigned char`. You can try to modify that. In the example, instead of:

    typedef CGAL::Labeled_image_mesh_domain_3<CGAL::Image_3,K> Mesh_domain;

use a different wrapper:

    typedef CGAL::Mesh_3::Image_to_labeled_function_wrapper<CGAL::Image_3,
                                                            K,
                                                            double> Wrapper;
    typedef CGAL::Labeled_image_mesh_domain_3<CGAL::Image_3,K,Wrapper> 
Mesh_domain;

I have tried on my Linux machine, and I was able to mesh your data set with 
that modified .cpp file.


-- 
Laurent Rineau, PhD
R&D Engineer at GeometryFactory           http://www.geometryfactory.com/
Release Manager of the CGAL Project       http://www.cgal.org/