[vtkusers] converting vtkImageData to vtkUnstructuredGrid

[Liam Kurmos]

Thanks David!

On Sat, Apr 9, 2011 at 11:27 AM, David E DeMarle
<dave.demarle at kitware.com> wrote:
> It produces voxel cells not tetrahedral cells, so the mapping is one to one.
>
> David E DeMarle
> Kitware, Inc.
> R&D Engineer
> 28 Corporate Drive
> Clifton Park, NY 12065-8662
> Phone: 518-371-3971 x109
>
>
>
> On Sat, Apr 9, 2011 at 3:59 AM, Liam Kurmos <quantum.leaf at gmail.com> wrote:
>> I've attempted to convert imagedata to unstructured data as you
>> suggested some time back using vtkthreshold.
>> In the code below vtkVol is a vtkImageData with scalar point data.
>> However when i query the number of cells in the output unstructured
>> grid i get the same as in the structured data. I would image there
>> should be twice as many unstructured tetrahedra as cells in the
>> structured data, can you comment on this?
>>
>> Liam
>>
>>
>>    vtkSmartPointer<vtkThreshold>
>> threshold=vtkSmartPointer<vtkThreshold>::New();
>>    threshold->SetInput(vtkVol);
>>    threshold->ThresholdByUpper(0);//scalars are all postive so threshold all
>>    vtkSmartPointer<vtkUnstructuredGrid> volumeMesh=threshold->GetOutput();
>>    threshold->Update();
>>    cout<<" vtkug num cells "<<volumeMesh->GetNumberOfCells()<<endl;
>>    cout<<" imagedata num cells "<<vtkVol->GetNumberOfCells()<<endl;
>>
>>
>>
>> On Wed, Feb 9, 2011 at 3:34 PM, David E DeMarle
>> <dave.demarle at kitware.com> wrote:
>>> Threshold and many other subsetting filters produce arbitrary sets of
>>> cells, thus by definition they can not produce structured data.
>>>
>>> David E DeMarle
>>> Kitware, Inc.
>>> R&D Engineer
>>> 28 Corporate Drive
>>> Clifton Park, NY 12065-8662
>>> Phone: 518-371-3971 x109
>>>
>>>
>>>
>>> On Wed, Feb 9, 2011 at 10:05 AM, Liam Kurmos <quantum.leaf at gmail.com> wrote:
>>>> Hi David,
>>>>
>>>> Thanks for replying.
>>>>
>>>>> One way is to apply the threshold filter and set the threshold so that
>>>>> it includes the entire scalar range.
>>>>
>>>> is it a side affect of the threshold filter that it will also produce
>>>> an unstructured grid from a structured one?
>>>>
>>>> cheers,
>>>>
>>>> Liam
>>>>
>>>
>>
>