[Insight-developers] Writing a SimplexMesh with SpatialObjectWriter

[Julien Jomier]

Jim,

I don't see any easy way to fix this problem. The main issue is that a 
->GetMesh() will fail on the MeshSpatialObject if the cast is not correct.

One other option is to template the SpatialObjectReader/Writer on the 
type of Mesh to write instead of the current MeshTrait...

I think it's a good idea to keep the MeshSpatialObject has a wrapper to 
the SimplexMesh.

Julien

Miller, James V (Research) wrote:
> I dont't think a static cast is a safe thing to do in this context.
> 
> Jim
> 
> -----Original Message-----
> From: Julien Jomier [mailto:jjomier at cs.unc.edu]
> Sent: Thursday, July 14, 2005 12:01 PM
> To: Miller, James V (Research)
> Cc: Insight-developers (E-mail)
> Subject: Re: [Insight-developers] Writing a SimplexMesh with
> SpatialObjectWriter
> 
> 
> Hi Jim,
> 
> Thanks for the report.
> How about replacing the dynamic_cast by a static_cast in MetaSceneConverter?
> 
> This option seems to work for me,
> Let me know,
> 
> Julien
> 
> Miller, James V (Research) wrote:
> 
>>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
>>
>>
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>>Insight-developers at itk.org
>>http://www.itk.org/mailman/listinfo/insight-developers
>>
>>
>>
> 
> 
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