[Insight-developers] itkVTKPolyDataReader.h reads ascii only--- why?

[Vincent Magnotta]

Brian,

I have taken the same approach as Slicer with this effort. Essentially a VTK
transform is generated from the direction cosines, spacing and origin. The
VTK image is then set to have an origin of 0,0,0 and spacing of 1,1,1. Once
the mesh is generated, the resulting poly data is transformed using the VTK
transform. The resulting pipeline is then

ITK-Image =>  VTK-Image => Change VTK Info => MarchingCube => VTK-Mesh
=> Transform VTK-Mesh => ITK-Mesh


Vince


On 10/19/10 10:40 PM, "brian avants" <stnava at gmail.com> wrote:

> Vince --- My understanding (though perhaps outdated?) is that vtk
> meshes lose direction information (obtained by calling GetDirection on
> an itk image) b/c a vtk image does not store this information.  So, if
> you create a pipeline like this:
> 
> ITK-Image =>  VTK-Image => MarchingCube => VTK-Mesh => ITK-Mesh
> 
> then you will lose the directionality information at the ITK to VTK
> stage.  Which is a problem if the direction is not the identity. The
> mesh, consequently, doesnt have orientation either, unless you
> explicitly set it yourself (not hard to do) by mapping the vtk-points
> through the orienting transformation.  So, maybe there is a filter
> that already does this or perhaps the vtk image object is updated and
> now stores the orientation?   Or maybe there's another vtk filter that
> should be inserted into the pipeline above to reorient the output of
> marching cubes back into ITK physical space?
> 
> B
> 
> 
> On Tue, Oct 19, 2010 at 10:55 PM, Magnotta, Vincent A
> <vincent-magnotta at uiowa.edu> wrote:
>> Brian,
>> 
>> I don't understand this question. Isn't the VTK point information already in
>> physical space? Maybe this is just how I have always dealt with the VTK
>> data. I believe that Slicer also follows this convention.
>> 
>> Vince
>> 
>> 
>> ----------------------
>> Associate Professor
>> Department of Radiology
>> 0453-D JCP
>> 200 Hawkins Drive
>> Iowa City, IA 52242
>> E-mail: vincent-magnotta at uiowa.edu
>> Phone: 319-356-8255 Fax: 319-353-6275
>> Website: http://www.radiology.uiowa.edu
>> 
>> 
>> 
>> -----Original Message-----
>> From: insight-developers-bounces at itk.org on behalf of brian avants
>> Sent: Tue 10/19/2010 2:57 PM
>> To: Alexandre GOUAILLARD
>> Cc: Insight-developers at itk.org; Luis Ibanez
>> Subject: Re: [Insight-developers] itkVTKPolyDataReader.h reads ascii only---
>> why?
>> 
>> Hi Alexandre, Wanlin , dev-list
>> 
>> Would it be possible to add a reference image space to the vtk reader?
>>  That is, because vtk files dont have physical space associated with
>> them, we could have an optional input to the filter that would
>> reorient the mesh using the space of the image from which the mesh was
>> originally derived.  I guess this should probably be a separate
>> unoriented to oriented mesh filter ... have you already resolved this
>> issue?
>> 
>> Brian
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> 
> 

----------------------
Associate Professor
Department of Radiology
0453-D JCP
200 Hawkins Drive
Iowa City, IA 52242
E-mail: vincent-magnotta at uiowa.edu
Phone: 319-356-8255 Fax: 319-353-6275
Website: http://www.radiology.uiowa.edu