- MarchingCube is now templated with the data type. It means that it now

internaly stores a Data_type[] array, instead of a double[] array. When
  Data_type==char, it uses the 8th of the memory! For a 3D images of 182MB
  (the "colon" image), that saves 1.2GB.
  As a side effect, MarchingCubes.cpp is renamed to MarchingCubes_impl.h
  (because it is now a template class).
- Use MarchingCube.set_ext_data, so that the 3D image and the MarchingCube
  object share the same (unsigned char*) array. That saves again a lot of
  memory.
- call MarchingCube::clean_temps *before* copying its result in the demo's
  internal structures.

My laptop with 2GB RAM can now call the marching cubes algorithm on the
colon 3D image. It uses 2.8GB of virtual memory, which is just below the
limit of 3GB (Linux's limit on x86 machines)!

Surface_mesher/demo/Surface_mesher/qt4-demo/CMakeLists.txt

@@ -40,7 +40,7 @@ if ( CGAL_FOUND AND QT_FOUND AND QGLVIEWER_FOUND )
   
   include_directories( ${QGLVIEWER_INCLUDE_DIR} )
 
-  set( sources colorlisteditor.cpp isovalues_list.cpp mainwindow.cpp polyhedral_surface.cpp surface_mesher.cpp viewer.cpp volume.cpp ../../../../Marching_cube/src/mc/MarchingCubes.cpp ../../../../Marching_cube/src/mc/ply.c)
+  set( sources colorlisteditor.cpp isovalues_list.cpp mainwindow.cpp polyhedral_surface.cpp surface_mesher.cpp viewer.cpp volume.cpp ../../../../Marching_cube/src/mc/ply.c)
   
   qt4_automoc( ${sources} )
 

Surface_mesher/demo/Surface_mesher/qt4-demo/volume.cpp

@@ -313,19 +313,21 @@ void Volume::display_marchin_cube()
       mc.init_all();
 
       // set data
-      for(unsigned int i=0;i<nx;i++)
-        for(unsigned int j=0;j<ny;j++)
-          for(unsigned int k=0;k<nz;k++)
-          {
-            const float& value = m_image.value(i,j,k);
-            mc.set_data(value,i,j,k);
-          }
+//       for(unsigned int i=0;i<nx;i++)
+//         for(unsigned int j=0;j<ny;j++)
+//           for(unsigned int k=0;k<nz;k++)
+//           {
+//             const float& value = m_image.value(i,j,k);
+//             mc.set_data(value,i,j,k);
+//           }
+      mc.set_ext_data(static_cast<unsigned char*>(m_image.image()->data));
       // compute scaling ratio
       const double xr = m_image.xmax() / nx;
       const double yr = m_image.ymax() / ny;
       const double zr = m_image.zmax() / nz;
 
       mc.run(isovalues_list->isovalue(isovalue_id), xr, yr, zr);
+      mc.clean_temps();
 
       std::vector<double> facets;
       mc.get_facets(facets);
@@ -349,7 +351,6 @@ void Volume::display_marchin_cube()
     timer.stop();
     not_busy();
 
-    mc.clean_temps();
     status_message(QString("Marching cubes...done (%2 facets in %1 s)").arg(timer.time()).arg(m_surface_mc.size()));
   }
   CGAL::Bbox_3 bbox(0,0,0,0,0,0);

Surface_mesher/demo/Surface_mesher/qt4-demo/volume.h

@@ -95,7 +95,7 @@ private:
 
   std::vector<Facet> m_surface;
   std::vector<Facet> m_surface_mc;
-  MarchingCubes mc ;
+  MarchingCubes<unsigned char> mc ;
   Tr del;            // 3D-Delaunay triangulation
 
   MainWindow* mw;