[vtkusers] Create "cuberille" kind of vtkPolyData from vtkImageData

[David Gobbi]

On Sun, Feb 3, 2013 at 1:18 PM, David Gobbi <david.gobbi at gmail.com> wrote:
> On Sun, Feb 3, 2013 at 1:02 PM, joopeter <joo.peter at gmail.com> wrote:
>> I am wondering what is the most straightforward way to create that kind of
>> mesh in VTK.
>>
>> You can check what is it here:
>> http://www2.imm.dtu.dk/~janba/gallery/polygonization.html
>> <http://vtk.1045678.n5.nabble.com/file/n5718248/cuberille-candypig.png>
>>
>> Obviously internal faces need to be avoided in the final mesh, that's why
>> vtkImageDataGeometryFilter is not OK I guess.
>>
>> I think the most complex part of this to *correctly set up the mesh
>> topology* (which vertexes are connected to which other)  and to *correctly
>> set up cell ordering*.
>>
>> I understand that the final mesh is aliased compared to what Marching Cubes
>> produces but for me this 'cuberille' behaviour is a must for my project.
>>
>> Any opinion and pseudocode are welcome!
>
> This might be possible as a two-stage process:
>
> 1) Use vtkThreshold to create a 3D mesh that only contains voxels
> above threshold.
>
> 2) Use vtkGeometryFilter to get all the polygons that make up the
> surface of the mesh.

Actually, since you've already used vtkImageDataGeometry filter, do this:

1) vtkImageDataGeometryFilter (extract the voxels)
2) vtkGeometryFilter (extract the external faces)

 - David