[Insight-developers] Writing a SimplexMesh with SpatialObjectWriter

[Miller, James V (Research)]

The following code:

SpatialObjectWriter<N, T, Traits>::Pointer writer = SpatialObjectWriter<N, T, Traits>::New();
MeshSpatialObject<SimplexMeshType>::Pointer so = MeshSpatialObject<SimplexMeshType>::New();
so->SetMesh( simplexMesh );
writer->SetFileName( "foo");
writer->SetInput( so );
writer->Update();

will crash because the MetaSceneConverter assumes that a MeshSpatialObject is always templated
over a Mesh and not a subclass of Mesh.  At line 508, there is code that essentially does

	dynamic_cast<MeshSpatialObject<Mesh<T, N, Traits> >( so );

When the SpatialObject, so, is a MeshSpatialObject<SimplexMesh<T, N, Traits> >, then the dynamic_cast
will fail because C++ cannot convert between MeshSpatialObjects templated over different types (even though 
the two type are related by inheritance).

This can be fixed on the user end by passing in MeshSpatialObjects templated over a Mesh instead of a 
SimplexMesh.  Then the user calls SetMesh() on the MeshSpatialObject, the pointer to the SimplexMesh
will be cast back to a pointer to a Mesh and the writer will work.  But this is a little clunky.  

Another solution would be to create a SimplexMeshSpatialObject class that is used for wrapping
a SimplexMesh.  But this is also clunky. I don't see why one shouldn't be able to use a MeshSpatialObject
to wrap a SimplexMesh.


It would be best if this is fixed at the MetaSceneConverter level.  I think the following code

    if(!strncmp((*it)->GetTypeName(),"MeshSpatialObject",17))
      {
      typedef itk::Mesh<PixelType,NDimensions,TMeshTraits> MeshType;
      MetaMeshConverter<NDimensions,PixelType,TMeshTraits> converter;
      MetaMesh* mesh = converter.MeshSpatialObjectToMetaMesh(
          dynamic_cast<itk::MeshSpatialObject<MeshType>*>((*it).GetPointer()));
      if((*it)->GetParent())
        {
        mesh->ParentID((*it)->GetParent()->GetId());
        }
      mesh->Name((*it)->GetProperty()->GetName().c_str());
      this->SetTransform(mesh, (*it)->GetObjectToParentTransform()) ;
      metaScene->AddObject(mesh);
      }

needs to somehow cast the mesh that is internal to the SpatialObject back to a Mesh.  So even if a
MeshSpatialObject is wrapping a subclass of Mesh, it could still be written to disk.



Jim Miller 
_____________________________________
Visualization & Computer Vision
GE Research
Bldg. KW, Room C218B
1 Research Circle, Schenectady NY 12309-1027

millerjv at reserch.ge.com <mailto:millerjv at reserch.ge.com>
(518) 387-4005, Dial Comm: 8*833-4005
Cell: (518) 505-7065, Fax: (518) 387-6981