[vtkusers] The confusion of vtkMarchingCubes

[Bill Lorensen]

Here is an example that uses Discrete Marching Cubes:
http://www.vtk.org/Wiki/VTK/Examples/Medical/Cxx/GenerateModelsFromLabels


On Wed, Apr 14, 2010 at 9:31 AM, 朱文武 <cool.wenwu at gmail.com> wrote:

> Karthik Krishnan, thanks for your great help!
> However, firstly, i still can not understand the mean of the
> parameter-value in the member function-SetValue(int i, double value) of
> vtkMarchingCubes. For example, if the value is set to 110 (The  type of
> dataset is bmp ),  which isosurfaces should be extracted? The structure
> whose gray value is 110 or all structures whose gray value is below 110 ?
> Could you tell me?！
> Secondly,  could you provide some examples for the vtkDiscreteMarchingCubes
> , though i read the help in the "vtk documentation",  there is no detailed
> example illustrating it.  I also do not know  how to color the result !
> From my perspective, we can control the color through vtkActor,  there are
> other methods to control the properties of parts of the actor?
>
> Thanks.
>
> Wenwu
>
>
>
>
> On Wed, Apr 14, 2010 at 5:17 PM, Karthik Krishnan <
> karthik.krishnan at kitware.com> wrote:
>
>> You could use vtkDiscreteMarchingCubes and color the result by cell data
>>
>> or
>>
>> pre-process your data to set all the non-foreground voxels to background,
>> (so as to make it bilelvel) and then run marching cubes to extract each
>> label.
>>
>> On Wed, Apr 14, 2010 at 4:44 AM, 朱文武 <cool.wenwu at gmail.com> wrote:
>>
>>> hi all,
>>>
>>>       A problem confused me. I need your help. The class vtkMarchingCubes
>>> has been adapted to construct a specified structure ( extract specified
>>> isosurface),  the member function— vtkMarchingCubes::setvalue(int i, double
>>> value) is used to specify a particular contour value.  The type of dataset i
>>> used was gray bmp image.  Suppose the dataset contains gray value: 91, 111,
>>> 121, 137.
>>> Now the problem is that if i want to construct the anatomy structure
>>> whose gray value is 111,  so the code i write is that
>>> SetValue(0, 111).  However,  the result of construction is that almost
>>> all anatomy structures whose gray value is 91, 121, 137 have been
>>> constructed too. Why is it happens? what's the difference between the gray
>>> value in the bmp image and the contour value in this function?  And how to
>>> construct a specified structure?
>>>
>>> If we set the parameter -value to 111,  according to the MC algorithm,
>>> the specified isosurface should be extracted.  Do i understand wrong !?
>>> On the other hand, if i want to extract multiple isosurface and control
>>> property of each isosurface such as colors, how to do it? The function
>>> SetValue(int i, double value) can not accomplish the task. Though we can add
>>> contour value by increasing the index-i, the output of the vtkMarchingCubes
>>> is combined to the subsequent filter. Can anyone provide help? Thanks very
>>> much !
>>>
>>> The relevant code and original image and result of the construction is
>>> attached:
>>>
>>> Code:
>>>     vtkBMPReader *Image= vtkBMPReader::New();
>>>     // read the dataset
>>>      Image->Update();
>>>
>>>     vtkMarchingCubes *skinExtractor= vtkMarchingCubes::New();//
>>> skinGray=220,tendon=10,radius=20,ulna=40,
>>>     skinExtractor->SetInputConnection(Image->GetOutputPort());
>>>     skinExtractor->SetValue(0,111);// input the gray value
>>>     skinExtractor->ComputeGradientsOn();
>>>     skinExtractor->ComputeScalarsOff();
>>>
>>>     vtkDecimatePro *vdeci;
>>>     vdeci->SetInputConnection(skinExtractor->GetOutputPort());//
>>>     vdeci->SetTargetReduction(0.6);//
>>>     vdeci->PreserveTopologyOn();//
>>>
>>>     vtkSmoothPolyDataFilter *vsmoother;
>>>     vsmoother->SetInputConnection(vdeci->GetOutputPort());//
>>>     vsmoother->SetNumberOfIterations(800);//
>>>
>>>     vtkPolyDataNormals *vskinNormal;
>>>     vskinNormal->SetInputConnection(vsmoother->GetOutputPort());//
>>>     vskinNormal->SetFeatureAngle(60.0);//
>>>
>>>     vtkPolyDataMapper *vskinMapper;
>>>     vskinMapper->SetInputConnection(vskinNormal->GetOutputPort());
>>>     vskinMapper->ScalarVisibilityOff();//
>>>
>>>     vtkActor *vskin;
>>>     vskin->SetMapper(vskinMapper);//
>>>     vskin->GetProperty()->SetColor(1,0,0);
>>>
>>> The original image :
>>> [image: TCVH_1300副本.bmp]
>>>
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>>
>>
>>
>>
>
>
> --
> 祝
> 工作愉快，身体健康！
>
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