[vtkusers] The confusion of vtkMarchingCubes

[朱文武]

Bill, thank you very much! Though i had found the site seconds before.
:)


Thanks.
Wenwu

On Wed, Apr 14, 2010 at 10:45 PM, Bill Lorensen <bill.lorensen at gmail.com>wrote:

> 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！
>>
>> _______________________________________________
>> Powered by www.kitware.com
>>
>> Visit other Kitware open-source projects at
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>>
>> Please keep messages on-topic and check the VTK FAQ at:
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>>
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祝
工作愉快，身体健康！
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